Methods We present an extension of previously published design (propensity score matching) and analysis (targeted maximum likelihood estimation) methods to evaluate the behavioural and health impacts of a pre-existing but non-randomized intervention (a 3-year, combined household water treatment and handwashing campaign in rural Guatemala). Six months after the intervention, we conducted a cross-sectional cohort study in 30 villages (15 intervention and 15 control) that included 600 households, and 929 children <5 years of age.

Results The study design created a sample of intervention and control villages that were comparable across more than 30 potentially confounding characteristics. The intervention led to modest gains in confirmed water treatment behaviour [risk difference = 0.05, 95% confidence interval (CI) 0.02–0.09]. We found, however, no difference between the intervention and control villages in self-reported handwashing behaviour, spot-check hygiene conditions, or the prevalence of child diarrhoea, clinical acute lower respiratory infections or child growth.

Conclusions To our knowledge this is the first post-intervention follow-up study of a combined household water treatment and handwashing behaviour change intervention, and the first post-intervention follow-up of either intervention type to include child health measurement. The lack of child health impacts is consistent with unsustained behaviour adoption. Our findings highlight the difficulty of implementing behaviour-based household water treatment and handwashing outside of intensive efficacy trials.

Methods Using linear regression we described the relationship between estimated ambient-erythemal ultraviolet (eUV) exposure in Oxford (1990–95) and total hours of sunshine and month in order to forecast eUV in nearby regions, whilst adjusting for regional variations in weather. The forecast was validated with empirical data collected from Cornwall and then predicted for the Avon region. Total 98-day prenatal ambient-eUV was then predicted in 355 expectant mothers in the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort and its relationship with maternal vitamin D status was determined.

Results Estimated ambient-eUV was strongly associated with measured ambient-eUV (r² = 0.989) with a near 1:1 prediction for the validation data set [β = 0.99, 95% confidence interval (CI) 0.913, 1.067 r² = 0.980]; strong seasonal associations were observed between eUV in the last trimester of pregnancy and maternal serum 25-(OH)D concentrations (r² = 0.40).

Conclusion This technique of prediction could be applied to existing cohorts allowing the relationship between maternal vitamin D status and the health of the offspring to be studied via instrumental variable analysis.

Methods A follow-up study was conducted for 16 828 men and 8368 women aged 30–59 years and apparently healthy at baseline. Incident DM was identified by ‘fasting serum glucose ≥7.00 mmol/l (126 mg/dl)’ or/and ‘under medical treatment for DM’. Using Cox proportional hazard models, hazard ratio (HR) for incident DM were estimated according to the quartiles of heart rate, systolic or diastolic BP (SBP, DBP), and its linear trends were checked by computing the three indices as continuous variables. Subsequently, interactive effects of slow/fast heart rate (dichotomized by the median) and low/high SBP or DBP (dichotomized by the median) on HR were examined. Baseline age, body mass index, smoking, drinking, exercise and education were computed as conventional confounders.

Results During the follow-up of 125 106 person-years for men and 59 616 person-years for women, 869 men and 224 women developed DM. The multivariate-adjusted HR for incident DM increased across quartiles of heart rate, SBP and DBP in both sexes (linear trend P<0.001 for all). Neither sex showed any significant interactive effects of heart rate and SBP or DBP on HR.

Conclusions Resting heart rate and BP proportionally raise the risk for DM in middle-aged healthy men and women. Moreover, the adverse effects of fast heart rate and high BP are independent of each other as well as of the influences of conventional confounders.

Methods A national cohort of 447 929 children born during 1973–77 was followed prospectively in the National Patient Discharge Register from the end of their ninth and last year of compulsory school until 2001. Multivariate Cox analyses of proportional hazards were used to test hypotheses regarding grades in ninth grade as predictors of hospital admission due to self-inflicted injury.

Results The risk of hospital admission because of self-inflicted injury increased steeply in a step-wise manner with decreasing grade point average. Hazard ratios were 6.2 (95% confidence interval 5.5–7.0) in those with the lowest level of grade point average compared with the highest. The risks were similar for women and men. Adjustment for potential socio-economic confounders in a multivariate proportional hazards regression analysis attenuated this strong gradient only marginally.

Conclusion School performance is a strong factor for predicting future mental ill-health as expressed by self-inflicted injury.

Methods This study was a population-based cohort study in a Japanese urban area. Study subjects were comprised of 5026 initially healthy Japanese (2370 men and 2656 women, mean age: 54.5 years) without a history of MI or stroke. They were followed-up for 11.8 years on average, and 103 MIs (definite: 45; probable: 58) and 168 strokes (definite: 126; probable: 42) were observed. There was no subject who developed MI just at baseline (the follow-up period among those with definite MI was, at earliest, 0.20 years).

Results The adjusted hazard ratio for definite MI was 4.18 (95% confidence interval 1.66–10.53) with s-CK levels of ≥200 IU/l, compared with the reference category (s-CK levels of ≤99 IU/l), whereas no relationship was observed between s-CK levels and the risk for stroke. With regard to definite MI, an interaction between s-CK levels and dyslipidaemia was observed. Among subjects with hypercholesterolaemia, the hazard ratio linearly elevated with increased s-CK levels. On the other hand, no linear elevation was observed among subjects without hypercholesterolaemia (P for interaction = 0.011).

Conclusions The present study suggested that screening for elevated s-CK levels in initially healthy Japanese subjects was useful to predict first-ever MI in the future, especially in subjects with dyslipidaemia.

Methods To avoid these biases we used a Mendelian randomization approach incorporating an analysis of variants in the FTO gene that are strongly associated with BMI levels among 7000 subjects from a study of lung, kidney and upper-aerodigestive cancer.

Results The FTO A allele which is linked with increased BMI was associated with a decreased risk of lung cancer (allelic odds ratio (OR) = 0.92, 95% confidence interval (CI) 0.84–1.00). It was also associated with a weak increased risk of kidney cancer, which was more apparent before the age of 50 (OR = 1.44, CI 1.09–1.90).

Conclusion Our results highlight the potential for genetic variation to act as an unconfounded marker of environmentally modifiable factors, and offer the potential to obtain estimates of the causal effect of obesity. However, far larger sample sizes than studied here will be required to undertake this with precision.

Methods We used twin data from the National Survey of Midlife Development in the United States, 1995–1996. The study population included 302 male [55.6% monozygotic (MZ) and 44.4% dizygotic (DZ)] and 387 female twin pairs (47.3% MZ and 52.7% DZ). A range of health outcomes [perceived global, physical and mental health, body mass index (BMI), waist circumference, waist–hip ratio, number of depressive symptoms] and health behaviours (smoking and physical activity) were examined among twin pairs who were discordant on years of schooling.

Results Among MZ twins, more years of education was associated with better perceived global health. For all other health outcomes/behaviours, the point estimates of the effect of education in the fixed-effect analyses suggested a weak protective association. Among DZ male twins, each additional year of schooling lowered the prevalence of smoking by 32% [odds ratio (OR): 0.68, 95% confidence interval (CI): 0.48–0.97] in the fixed-effect analysis.

Conclusion The widely reported associations between schooling and health outcomes/behaviours may not reflect causal relationships in every instance. Although low statistical power may explain some of the null associations, our twin fixed-effect analyses suggest that at least some cases of the education/health relationship reflect confounding by unobserved third variables.

Methods A community-based cross-sectional tuberculosis (TB) disease prevalence survey was undertaken among adults aged ≥15 years in the tribal population of Madhya Pradesh. A multistage stratified cluster sampling was adopted. A representative random sample of villages predominated by tribal populations was selected from 11 districts. All eligible individuals were questioned for chest symptoms relating to TB. Sputum samples were collected from all eligible individuals, transported to the laboratory, and examined by Ziehl–Neelsen (ZN) smear microscopy and solid media culture methods.

Results Of the 23 411 individuals eligible for screening, 22 270 (95.1%) were screened for symptoms. The overall proportion of symptomatic individuals was 7.9%. Overall prevalence (culture and/or smear positive) of PTB was 387 [95% confidence interval (CI): 273–502] per 100 000 population. The prevalence increased with age and was also significantly higher among males (554/100 000; 95% CI: 415–693) as compared with females (233/100 000; 95% CI: 101–364) (P < 0.001).

Conclusion The findings suggest that the TB situation amongst the tribal population is not that different from the situation among the non-tribal population in the country. However, TB remains a major public health problem amongst the tribal population and there is a need to maintain and further strengthen TB control measures on a sustained and long-term basis.

Methods A total of 1839 males and 870 females treated in 2000–03 by state TB clinics were interviewed at home in 2004–05 about their education, smoking and drinking habits before disease onset. As controls, 2134 men and 2119 women without TB were randomly chosen from case villages and interviewed. Incidence rate ratios (RRs) are from logistic regression, adjusted for age and education.

Results No women smoked or drank. The main analyses are of men aged 35–64 years, 949 cases treated for new pulmonary TB and 1963 controls. In the study, 81.5% of the cases and 55.2% of the controls had ever smoked, yielding a standardized ever- vs never-smoker TB incidence RR of 2.7 [95% confidence interval (CI) 2.2–3.3, P < 0.00001). Among control ever-smokers 96% still smoked, 71% used only bidis (mean 17 per day) and 28% used only cigarettes (mean 7 per day). After additional adjustment for alcohol, this RR was 2.2 (95% CI 1.7–2.7, P < 0.00001), but even among those who had never drunk alcohol the standardized ever- vs never-smoker RR was 2.6 (95% CI 2.0–3.6, P < 0.00001). The corresponding RRs for ever- vs never-drinking were somewhat less extreme: 2.2 (95% CI 1.8–2.6, P < 0.00001) without adjustment for smoking, 1.5 (95% CI 1.2–1.9, P = 0.00004) with adjustment for smoking and 2.1 (95% CI 1.4–3.0, 2P = 0.0001) among those who had never smoked. Among control ever-drinkers, 96% still drank and 99% used only spirits (mean 0.3 l/week).

Conclusions This study of reliably confirmed disease (by the criteria of state TB clinics) demonstrates an increased incidence of pulmonary TB among those who smoke and among those who drink. The effects of smoking after adjustment for drinking were more definite than those of drinking after adjustment for smoking.

Methods Maternal anthropometry, dietary intakes (24-h recall and food-frequency questionnaire) and activity pattern (questionnaire) at 18 ± 2 and 28 ± 2 weeks gestation, and neonatal anthropometry, were measured in a prospective study of 797 rural Indian women.

Results Maternal energy and protein intakes were inadequate (70% of recommended dietary allowance). Both intake and activity showed seasonal variation (P = 0.001), with peak values in winter i.e. during harvest, at 18 weeks (median energy 1863 kcal/day, protein 47.5 g/day) and 28 weeks (median energy 1687 kcal/day, protein 43.7 g/day), coinciding with the maximum maternal activity (median score 86.1 at 18 weeks and 79.5 at 28 weeks). Mean birth weight and length (adjusted for pre-pregnant weight, parity, gestation and sex) of babies was highest in summer (peak at February 2733 g, 48.6 cm, respectively) and lowest in winter (nadir at January 2591 g, 47.1 cm, respectively). Regression analysis showed that maternal intake at 18th week had a positive association (P = 0.05), maternal activity at 28th week had a negative association (P = 0.002) and exposure (in weeks) to winter during gestation had a positive association (P = 0.04) with birth size. Furthermore, higher maternal intakes, coupled with lower maternal activity in late gestation were associated with higher birth weight, especially during winter.

Conclusions If causal, these observations indicate that complete exposure (16 weeks) to the winter season (harvest-time) in late gestation could increase birth weight by 90 g in poor farming communities in rural India, and the benefit would increase further by lowering maternal activity. Our results underscore the importance of considering seasonality in planning targeted intervention strategies in such settings.

Methods Spatial accessibility, as measured by network travel times, to 457 grocery stores located in 205 neighbourhoods in four environmental settings (island, rural, small town and urban) in Scotland was calculated using Geographical Information Systems. The distribution of accessibility by neighbourhood deprivation in each of these four settings was investigated.

Results Overall, the most deprived neighbourhoods had the best access to grocery stores and grocery stores selling fresh produce. Stratified analysis by environmental setting suggests that the least deprived compared with the most deprived urban neighbourhoods have greater accessibility to grocery stores than their counterparts in island, rural and small town locations. Access to fresh produce is better in more deprived compared with less deprived urban and small town neighbourhoods, but poorest in the most affluent island communities with mixed results for rural settings.

Conclusions The results presented here suggest that the assumption of a universal ‘deprivation amplification’ hypothesis in studies of the neighbourhood food environment may be misguided. Associations between neighbourhood deprivation and grocery store accessibility vary by environmental setting. Theories and policies aimed at understanding and rectifying spatial inequalities in the distribution of neighbourhood exposures for poor diet need to be context specific.

Methods A cross-sectional survey with face-to-face interviews of rural and urban residents in northern China. Before providing any information, we asked the residents whether they would accept drug treatment if they had hypertension and also asked them to estimate the 5-year cardiovascular risk in untreated hypertension and the benefits from anti-hypertensive drugs. We then informed the participants of necessary information and asked them above what benefit they would be willing to pay the current cost, and how much they would be willing to pay for the actual benefit, for anti-hypertensive drugs out of pocket.

Results Eight hundred and eighty-seven rural residents and 921 urban residents were interviewed with a response rate of 97%. Ninety-five percent [95% confidence interval (CI) 94–96%] of the residents said they would take anti-hypertensive drugs if they had hypertension, although 91% (95% CI 89–92%) said they did not have sufficient knowledge to make a decision. Seventy-eight percent (95% CI 76–80%) believed that anti-hypertensive drugs were primarily to lower blood pressure or relieve symptoms. They over-estimated the cardiovascular risk of untreated hypertension by approximately 12 times and the absolute benefit of drug treatment by 20 times. Given the actual absolute benefit of the drugs, only 23% (95% CI 21–25%) were willing to pay the current annual cost of $500 Ren Min Bi (US$73.3, 54.8 as of 8 May 2009) for these drugs. Given the current cost, they were, on average, willing to pay for the drugs only when the 5-year cardiovascular disease risk was as high as 35% (95% CI 31–38%) or even higher.

Conclusion The public in China are significantly misinformed and considerably over estimate the risk of hypertension and the benefit of treatment. The public's willingness to pay for anti-hypertensive drugs is much lower than the current guidelines implicitly assume. The willingness to pay should be considered, along with other factors, when prescribing anti-hypertensive drugs to an individual patient or making hypertension guidelines for a population.

Methods A model based on consumption data and demand elasticity was constructed to predict the effects of four food taxation-subsidy regimens. Resulting changes in demand, expenditure, nutrition, cardiovascular disease (CVD) and cancer mortality were estimated.

Data Expenditure data were taken from the Expenditure and Food Survey; estimates of price elasticities of demand for food were taken from a report based on the National Food Survey 1988–2000. Estimates of effect on CVD and cancer mortality of changing fat, salt, fruit and vegetable intake were taken from previous meta-analyses.

Results (i) Taxing principal sources of dietary saturated fat is unlikely to reduce cardiovascular disease (CVD) or cancer mortality. (ii) Taxing ‘less healthy’ foods (defined by the WXYfm nutrient profiling model) could increase CVD and cancer deaths by 35–1300 yearly. (iii) Taxing ‘less healthy’ foods and subsidising fruits and vegetables by 17.5% could avert up to 2900 CVD and cancer deaths yearly. (iv) Taxing ‘less healthy’ foods and using all tax revenue to subsidize fruits and vegetables could avert up to 6400 CVD and cancer deaths yearly. Few obesity-related CVD deaths are averted by any of the regimens. All four regimens would be economically regressive and positive health effects will not necessarily be greater in lower-income groups where the need for dietary improvement is higher.

Conclusions A targeted food tax combined with the appropriate subsidy on fruits and vegetables could reduce deaths from CVD and cancer.

Methods A randomized experiment was embedded in a telephone survey that drew probability samples of the populations of the USA (N = 1543) and Baltimore city (N = 744). Respondents were randomly assigned to have questions asked either by a T-ACASI computer or by a human telephone interviewer.

Results Compared with interviewer-administered telephone surveys, T-ACASI obtained more frequent reporting of a range of mainly heterosexual behaviours that were presumed to be sensitive, including recency of anal sex [adjusted odds ratio (A-OR) = 2.00, P < 0.001), sex during menstrual period (A-OR = 1.49, P < 0.001), giving oral sex (A-OR = 1.40, P = 0.001) and receiving oral sex (A-OR = 1.36, P = 0.002), and sexual difficulties for the respondent (A-OR = 1.45, P = 0.034) and their main sex partner (A-OR = 1.48, P = 0.0). T-ACASI also obtained less frequent reporting that respondent had a ‘main sex partner’ (A-OR = 0.56, P = 0.011) and discussed contraception prior to first sex with that sex partner (A-OR = 0.82, P = 0.094). For both males and females, T-ACASI obtained more frequent reports of first vaginal sex occurring at early ages (before ages 12 through 15). ‘For males only’, T-ACASI also elicited more frequent reports that first vaginal sex had ‘not’ occurred at later ages (i.e. by ages 20 through 24).

Conclusion T-ACASI increases the likelihood that survey respondents will report sensitive heterosexual behaviours.

Methods We analysed data from ART-naïve, TB disease-free children enrolled between December 2004 and April 2008 into an HIV care program in Kinshasa, Democratic Republic of Congo. To estimate the effect of ART on TB incidence while accounting for time-dependent confounders affected by exposure, a Cox proportional hazards marginal structural model was used.

Results 364 children contributed 596.0 person-years of follow-up. At baseline, the median age was 6.9 years; 163 (44.8%) were in HIV clinical stage 3 or 4. During follow-up, 242 (66.5%) children initiated ART and 81 (22.3%) developed TB. At TB diagnosis, 41 (50.6%) were receiving ART. The TB incidence rate in those receiving ART was 10.2 per 100 person-years [95% confidence interval (CI) 7.4–13.9] compared with 20.4 per 100 person-years (95% CI 14.6–27.8) in those receiving only primary HIV care. TB incidence decreased with time on ART, from 18.9 per 100 person-years in the first 6 months to 5.3 per 100 person-years after 12 months of ART. The model-estimated TB hazard ratio for ART was 0.51 (95% CI 0.27–0.94).

Conclusions For HIV-infected children in TB-endemic areas, ART reduces the hazard of developing TB by 50%.

Methods Stepwise regression of annual data was applied to model incidence, calculated based on 91 cases, from lagged variables: antecedent precipitation, air temperature, soil water storage, absolute and relative air humidity, and Southern Oscillation Index (SOI).

Results Multiple regression analyses resulted in a model, which explains 49% of the incidence variance, taking into account the absolute air humidity in the year of exposure, soil water storage and SOI of the previous 2 years.

Conclusions The correlations may reflect enhanced fungal growth after increase in soil water storage in the longer term and greater spore release with increase in absolute air humidity in the short term.

Methods A sample of 1029 children was drawn from Birth to Twenty, a longitudinal cohort followed from pregnancy to young adulthood. This sample completed the Youth Self Report at age 12 years, a validated psychological measure of behavioural and emotional adjustment. Scores were compared between LBW (<2500 g) and normal birthweight children using multivariate analysis with adjustment for potential birth and life events confounding factors.

Results No associations were found between LBW and total [adjusted odds ratio (OR) 1.09, 95% confidence interval (CI) 0.69–1.74], internalizing (adjusted OR 0.81, 95% CI 0.52–1.28) or externalizing profiles (adjusted OR 0.81, 95% CI 0.49–1.36). The only difference detected was for the internalizing sub-profile of Somatic Complaints (adjusted OR 2.02, 95% CI 1.21–3.38), which on subgroup analysis was greatest among females.

Conclusions We found no convincing evidence of an association between LBW and emotional and behavioural outcomes in 12-year olds in this sample in urban South Africa. To our knowledge, this is the first published assessment of this association in a developing world context.

Methods We completed a cross-sectional study of a community sample of 3700 men aged ≥70 years, and used the 15-item Geriatric Depression Scale (GDS-15) to assess depressive symptoms. A GDS-15 score 7 or more indicates the presence of clinically significant depressive symptoms. Physical morbidity was assessed with the physical component summary score (PCS) of the SF-36 Health Survey. We collected fasting blood samples to measure high sensitivity CRP and to extract DNA for the genotyping of SNPs rs1130864 and rs1205 of the CRP gene.

Results One hundred and eighty-two men were depressed (4.9%). The odds of depression increased by 2% (95% CI = 1–4%) for every unit (mg/l) increase of CRP and nearly doubled for men with CRP ≥ 3 mg/l vs <1 mg/l [odds ratio (OR) = 1.95, 95% confidence interval (CI) = 1.27–2.98]. However, the association between high CRP (≥3 mg/l) and depression was no longer significant after the analyses were adjusted for smoking, age, body mass index (BMI) and PCS. Men with the CT and TT genotypes of rs1130864 had 1.36 (95% CI = 1.13–1.63) and 2.31 (95% CI = 1.65–3.24) greater odds of CRP ≥3 mg/l than CC carriers, but there was no association between this polymorphism and the presence of prevalent depression. The G > A polymorphism of SNP rs1205 was associated with 24% (95% CI = 16–32%) lower concentration of CRP compared with other genotypes. Men with the rs1205 AA genotype had 1.66 (95% CI = 1.07–2.57) and 1.67 (95% CI = 1.08–2.58) greater odds of having clinically significant depression than participants with the GA and GG genotypes, respectively.

Conclusion Our study shows that clinically significant depressive symptoms in later life are unlikely to be caused by an increase in the serum concentration of CRP. Instead, we found that the risk of depression was greater amongst people who carry the rs1205 G > A genetic polymorphism of the CRP gene, which was associated with ~20% lower serum concentration of CRP compared with other genotypes. This suggests that CRP may be a compensatory response to external insults that predispose to depression, and that an increase in the concentration of CRP might be adaptive.

Methods Data from individual studies and review articles known to the authors were examined. A Medline bibliographic database search was also performed. Reference lists were reviewed to identify additional relevant data sources. Key references were examined by both authors.

Results We propose, and evaluate, the evidence for a ‘mitochondrial efficiency hypothesis’ i.e. that ancestral changes in mitochondrial coupling efficiency enhanced the successful adaptation of South Asians to environmental stressors by maximizing the conversion of energy to adenosine triphosphate (ATP) rather than heat. This adaptation may be disadvantageous when South Asians are physically inactive and consume high-caloric diets. There is evidence that common mitochondrial mutations vary geographically. Mutations, including those affecting the function of mitochondrial uncoupling proteins (UCPs), may influence the balance of energy and heat production. These may influence basal metabolic rate (BMR), energy efficiency, the tendency to gain weight and hence metabolic disease. UCP gene polymorphisms are related to differences in BMR between African-Americans and Europeans. Similar data for South Asians are lacking but the few studies comparing BMR indicate that South Asians have a lower BMR, which is explained by a lower lean body mass, and higher fat mass. Once adjusted for body composition, BMR is similar. A high fat mass, per se, is a strategy for reducing energy use while conserving body size. Indians in the USA had higher oxidative phosphorylation capacity than Northern European Americans.

Conclusion The evidence justifies full exploration of this mitochondrial effeciency hypothesis in South Asians, which may also be relevant to other warm-climate adapted populations.

Methods This study included 832 children who were members of the Collaborative Perinatal Project. Maternal serum collected between 1959 and 1966 during the third trimester of pregnancy was analysed for free cortisol. We investigated the relationship between maternal cortisol in quintiles and full, verbal and performance scale scores on the Wechsler Intelligence Scale for Children at age 7 years, adjusting for prenatal and family characteristics. We repeated this analysis among 74 discordant sibling pairs using a fixed effects approach, which adjusts for shared family characteristics.

Results Maternal cortisol levels were negatively related to full-scale IQ, an effect driven by verbal IQ scores. Compared with those in the lowest quintile of cortisol exposure, the verbal IQ of children in the highest quintile of exposure was 3.83 points lower [95% confidence interval (CI): –6.44 to –1.22]. Within sibling pairs, being in the highest quintile of exposure was associated with verbal IQ scores 5.5 points lower (95% CI: –11.24 to 0.31) compared with the other quintiles.

Conclusion These findings are consistent with prior human and animal studies, and suggest that exposure to high levels of maternal cortisol during pregnancy may be negatively related to offspring cognitive skills independently of family attributes that characterize the postnatal environment.

Methods Data were obtained from a population-based case–control study conducted between 2003 and 2007 with 300 histologically proven OSCC cases and 571 matched neighbourhood controls. We used conditional logistic regression to compare cases and controls for individual SES indicators, for a composite wealth score constructed using multiple correspondence analysis, and for factors obtained from factors analysis.

Results We found that various dimensions of SES, such as education, wealth and being married were all inversely related to OSCC. The strongest inverse association was found with education. Compared with no education, the adjusted odds ratios (95% confidence intervals) for primary education and high school or beyond were 0.52 (0.27–0.98) and 0.20 (0.06–0.65), respectively.

Conclusions The strong association of SES with OSCC after adjustment for known risk factors implies the presence of yet unidentified risk factors that are correlated with our SES measures; identification of these factors could be the target of future studies. Our results also emphasize the importance of using multiple SES measures in epidemiological studies.

Methods The theory is based on nocturnal light-induced disruption of circadian rhythms, notably reduction of melatonin synthesis. It has formed the basis for a series of predictions including that non-day shift work would increase risk, blind women would be at lower risk, long sleep duration would lower risk and community nighttime light level would co-distribute with breast cancer incidence on the population level.

Results Accumulation of epidemiological evidence has accelerated in recent years, reflected in an International Agency for Research on Cancer (IARC) classification of shift work as a probable human carcinogen (2A). There is also a strong rodent model in support of the light-at-night (LAN) idea.

Conclusion If a consensus eventually emerges that LAN does increase risk, then the mechanisms for the effect are important to elucidate for intervention and mitigation. The basic understanding of phototransduction for the circadian system, and of the molecular genetics of circadian rhythm generation are both advancing rapidly, and will provide for the development of lighting technologies at home and at work that minimize circadian disruption, while maintaining visual efficiency and aesthetics. In the interim, there are strategies now available to reduce the potential for circadian disruption, which include extending the daily dark period, appreciate nocturnal awakening in the dark, using dim red light for nighttime necessities, and unless recommended by a physician, not taking melatonin tablets.

Methods Seventy-eight independent retrospective cohort (incidence between 1984 and 2000, followed until 2006) outcomes were synthesized. Fixed effects meta-regression models compared women with breast cancer in low-income areas of Canada and the USA.

Results Low-income Canadian women were advantaged on survival [rate ratio (RR) = 1.14; 95% confidence interval (CI) 1.13–1.15] and their advantage was even larger among women <65 years of age who are not yet eligible for Medicare coverage in the USA (RR = 1.21, 95% CI 1.18–1.24). Canadian advantages were also larger for node positive breast cancer, which may present with greater clinical and managerial discretion (RR = 1.40, 95% CI 1.30–1.50), and smaller when Hawaii, the state providing the most Canadian-like access, was the US comparator (RR = 1.12, 95% CI 1.01–1.20).

Conclusions More inclusive health care insurance coverage in Canada vs the USA, particularly among each country's relatively poor people, seems the most plausible explanation for such Canadian advantages. Provision of health care for all Americans would likely prevent countless early deaths, particularly among the relatively poor.

Methods This was a prospective cohort study. Participants consisted of 13 621 men and women from the Aerobics Center Longitudinal Study (ACLS). Participants completed a clinical exam and 3-day diet record between 1987 and 1999. Participants were followed for mortality until 2003. Reduced rank regression (RRR) was used to identify dietary patterns that predicted unfavourable total and high-density lipoprotein-cholesterol, triglyceride, glucose, blood pressure, uric acid, white blood cell and body mass index values.

Results One primary dietary pattern emerged and was labelled the Unhealthy Eating Index. This pattern was characterized by elevated consumption of processed and red meat, white potato products, non-whole grains, added fat and reduced consumption of non-citrus fruits. The hazard ratio for all-cause mortality in the fifth vs the first quintile of the Unhealthy Eating Index was 1.40 (1.02–1.91). This risk estimate was reduced by 13.5 and 55.0% after controlling for self-reported physical activity and fitness, respectively.

Conclusion In this study the association between diet and overall mortality was, in large part, confounded by fitness.

Methods Cross-sectional study of urban primary school children (2006–07). Actigraph-GT1M activity monitors were worn by 2071 children during waking hours on at least 1 full day. Ethnic differences in mean daily activity [counts, counts per minute of registered time (CPM) and steps] were adjusted for age, gender, day of week and month. Multilevel modelling allowed for repeated days within individual and clustering within school.

Results In white Europeans, mean daily counts, CPM and mean daily steps were 394 785, 498 and 10 220, respectively. South Asian and black Caribbean children recorded more registered time per day than white Europeans (34 and 36 min, respectively). Compared with white Europeans, South Asians recorded 18 789 fewer counts [95% confidence interval (CI) 6390–31 187], 41 fewer CPM 95% CI 26–57) and 905 fewer steps (95% CI 624–1187). Black African–Caribbeans recorded 25 359 more counts (95% CI 14 273–36 445), and similar CPM, but fewer steps than white Europeans. Girls recorded less activity than boys in all ethnic groups, with 74 782 fewer counts (95% CI 66 665–82 899), 84 fewer CPM (95% CI 74–95) and 1484 fewer steps (95% CI 1301–1668).

Conclusion British South Asian children have lower objectively measured physical activity levels than European whites and black African–Caribbeans.

Methods We estimated the food energy required to maintain basal metabolic rate in two hypothetical adult populations using the Schofield equations for males and females. Additional greenhouse gas emissions due to higher fuel energy use for transporting a heavier population were estimated.

Results Compared with a normal population distribution of BMI, a population with 40% obese requires 19% more food energy for its total energy expenditure. Greenhouse gas emissions from food production and car travel due to increases in adiposity in a population of 1 billion are estimated to be between 0.4 Giga tonnes (GT) and 1.0 GT of carbon dioxide equivalents per year.

Conclusions The maintenance of a healthy BMI has important environmental benefits in terms of lower greenhouse gas emissions.

Methods Methodological review to address the concept of external validity.

Results External validity refers to the question whether results are generalizable to persons other than the population in the original study. The only formal way to establish the external validity would be to repeat the study for that specific target population. We propose a three-way approach for assessing the external validity for specified target populations. (i) The study population might not be representative for the eligibility criteria that were intended. It should be addressed whether the study population differs from the intended source population with respect to characteristics that influence outcome. (ii) The target population will, by definition, differ from the study population with respect to geographical, temporal and ethnical conditions. Pondering external validity means asking the question whether these differences may influence study results. (iii) It should be assessed whether the study's conclusions can be generalized to target populations that do not meet all the eligibility criteria.

Conclusion Judging the external validity of study results cannot be done by applying given eligibility criteria to a single target population. Rather, it is a complex reflection in which prior knowledge, statistical considerations, biological plausibility and eligibility criteria all have place.

Methods Using a case–control design, we analysed data from 97 215 women of the Etude Epidémiologique auprès de femmes de l’Education Nationale study, a cohort of 98 995 French women insured by a national health scheme mostly covering teachers, and aged 40–65 years at inclusion in 1990. Risk estimates were computed using unconditional logistic regression models.

Results After adjustment for potential confounding factors, there was a positive dose–effect relationship between risk of endometriosis (reported as surgically ascertained, n = 4241) and skin sensitivity to sun exposure [moderate: odds ratio (OR) 1.09, 95% confidence interval (CI) 0.99–1.19; high: OR 1.22; 95% CI 1.10–1.36; compared with none; P_trend < 0.0001], number of naevi (few: OR 1.19, 95% CI 1.05–1.35; many: OR 1.37, 95% CI 1.21–1.55; very many: OR 1.59, 95% CI 1.37–1.83; compared with none; P_trend < 0.0001) and number of freckles (few: OR 1.08, 95% CI 1.00–1.17; very many/many: OR 1.11, 95% CI 1.03–1.20; compared with none; P_trend = 0.005).

Conclusion This study is, to our knowledge, the first to report a positive dose–effect relationship between the risk of endometriosis and skin sensitivity to sun exposure, and number of naevi and freckles. These data suggest that endometriosis and melanoma may share some genetic features.

Methods Population-based cohort study of 35 846 men and women born between 1920 and 1959 with mortality follow-up from 1961 to 2005.

Results During follow-up, 630 people died from CHD and there was an inverse association of head circumference with deaths from CHD (P_trend = 0.010). The association was modified by maternal height (P_interaction = 0.01) and by adult body mass (P_interaction = 0.05). People in the lowest third of head circumference, who had a tall mother or a high body mass index in adulthood, were at the highest risk of death from CHD.

Conclusions Head circumference at birth was inversely associated with deaths from CHD, and the combination of small head and tall mother, or small head and high adult body mass, was associated with the highest risk. These findings suggest that combined effects of genetic factors (growth potential and intrauterine growth) and non-genetic factors acting throughout the life course (intrauterine growth restriction and later weight gain) could mediate the effects of birth size on adult heart disease.

Methods We analysed data from a prospective study of hormonal contraception and HIV acquisition among Zimbabwean and Ugandan women (1999–2004), in which HIV testing and counselling were performed approximately every 3 months. We used zero-inflated negative binomial (ZINB) models to examine the number and proportion of unprotected sex acts, comparing behaviour reported 2–6 months before HIV testing with behaviour reported both 2–6 months (short-term analysis) and 12–16 months (long-term analysis) after HIV testing.

Results Short- and long-term analyses were similar, so we present only long-term findings from 151 HIV-infected and 650 uninfected participants. The proportion of HIV-infected women reporting any unprotected acts in a typical month declined from 74% (pre-infection behaviour) to 56% (12–16 months after HIV diagnosis). In multivariable models, HIV-infected women were twice as likely to report that all sex acts were protected by condoms after diagnosis compared with beforehand [adjusted odds ratio (aOR): 1.99, 95% confidence interval (CI): 1.12–3.53]; uninfected women were somewhat less likely to report that all acts were protected (aOR: 0.82, 95% CI: 0.64–1.04). HIV-infected women also reduced their number of unprotected acts by 38% (95% CI: –16 to –55%). However, their proportion of unprotected acts changed little (7% reduction, 95% CI: –18 to + 6%). Uninfected women reported little change in number or proportion of unprotected acts over the same time period.

Conclusions HIV-infected women reduced the number, but not the proportion, of unprotected acts. HIV-negative women did not increase condom use after testing and counselling, but neither did they decrease condom use, suggesting that testing negative was not interpreted as endorsement of risky behaviour.

Methods A systematic review was conducted to explore the relationship between fatigue, chronic fatigue (CF—fatigue lasting for 6 months), CFS and ethnicity. Studies were population-based and health service-based. Meta-analysis was also conducted to examine the population prevalence of CF and CFS across ethnic groups.

Results Meta-analysis showed that compared with the White American majority, African Americans and Native Americans have a higher risk of CFS [Odds Ratio (OR) 2.95, 95% confidence interval (CI): 0.69–10.4; OR = 11.5, CI: 1.1–56.4, respectively] and CF (OR = 1.56, CI: 1.03–2.24; OR = 3.28, CI: 1.63–5.88, respectively). Minority ethnic groups with CF and CFS experience more severe symptoms and may be more likely to use religion, denial and behavioural disengagement to cope with their condition compared with the White majority.

Conclusions Although available studies and data are limited, it does appear that some ethnic minority groups are more likely to suffer from CF and CFS compared with White people. Ethnic minority status alone is insufficient to explain ethnic variation of prevalence. Psychosocial risk factors found in high-risk groups and ethnicity warrant further investigation to improve our understanding of aetiology and the management of this complex condition.

Methods National legislation case analysis.

Results In accordance with European regulation, French observational studies from data obtained without any additional therapy or monitoring procedure, do not need the approval of an IRB/IEC. Nevertheless, these studies are neither exempt from scientific opinion nor from ethical and legal authorization.

Conclusion We wish to demonstrate through the study of this example that different bodies of law can provide equivalent levels of protection that respect the same ethical principles. Our purpose in writing this article was to encourage public bodies, scientific journals and researchers to gain a better understanding of the various sets of specific national regulations and to speak a common language.

Methods Abridged period lifetables for Maori and non-Maori from 1951 to 2006 were constructed using standard demographic methods. Absolute [standardized rate difference (SRD)] and relative [standardized rate ratio (SRR)] mortality inequalities for Maori compared with European/Other ethnic groups (aged 1–74 years) were measured using the New Zealand Census-Mortality Study (an ongoing data linkage study that links mortality to census records) from 1981–84 to 2001–04. The SRDs were decomposed into their contributions from major causes of death. Poisson regression modelling was used to estimate the extent of socio-economic mediation of the ethnic mortality inequality over time.

Results Life expectancy gaps and relative inequalities in mortality rates (aged 1–74 years) widened and then narrowed again, in tandem with the trends in social inequalities (allowing for a short lag). Among females, the contribution of cardiovascular disease to absolute mortality inequalities steadily decreased, but was partly offset by an increasing contribution from cancer. Among males, the contribution of CVD increased from the early 1980s to the 1990s, then decreased again. The extent of socio-economic mediation of the ethnic mortality inequality peaked in 1991–94, again more notably among males.

Conclusion Our results are consistent with a causal association between changing economic inequalities and changing health inequalities between ethnic groups. However, causality cannot be established from a historical analysis alone. Three lessons nevertheless emerge from the New Zealand experience: the lag between changes in ethnic social inequality and ethnic health inequality may be short (<5 years); both changes in the distribution of the social determinants of health and an appropriate health system response may be required to address ethnic health inequalities; and timely monitoring of ethnic health inequalities, based on high-quality ethnicity data, may help to sustain political commitment to pro-equity health and social policies.

Methods We address the logic of the implicit argument that the transient infections were an artifact and we demonstrate a simple likelihood calculation to assess the plausibility of competing explanations. We calculate the likelihood of observing our data based on a range of clearance and measurement error rates and then how this updates a set of prior beliefs.

Results The likelihood calculations and resulting posterior probabilities show strong support for the hypothesis of spontaneous clearance, after allowing for measurement error, even starting with a very high prior probability of no spontaneous clearance. The scenario Perry and Parsonnet present is incompatible with our data, and thus not a plausible explanation for our observations. Attributing most observed transient infections to measurement error requires assuming a high false positive rate and a very low infection rate and/or a high false negative rate, alternatives that are not supported by evidence.

Conclusions Acknowledgment of plausible levels of measurement error does not change the strong support our data provides for the hypothesis of frequent transient infection. Debate about competing explanations for observations should be accompanied by quantitative analysis that shows which is more plausible. We demonstrate one method for doing such analysis.

Methods Thirty-nine studies from the Asia Pacific Cohort Studies Collaboration database were included. We used Cox proportional hazard regression models to estimate the associations between height and pre-specified outcomes.

Results A total of 510 800 participants with 21 623 deaths were included. Amongst men, inverse linear associations were observed between height and coronary heart disease (CHD), stroke, CVD, injury and total mortality. The hazard ratios [95% confidence intervals, (CI)] for a 1-SD (= 6 cm) increment in height ranged from 0.85 (0.80–0.91) for injury to 0.97 (0.95–0.98) for total mortality. Similar trends were found between height and CHD, haemorrhagic stroke and CVD in women. A positive linear association was observed between height and cancer mortality. For each standard deviation greater height, the risk of cancer was increased by 5% (2–8%) and 9% (5–14%) in men and women, respectively. No regional difference was observed between Asian and Australasian cohorts. Adjusting for markers of education did not alter the results.

Conclusions The opposing relationships of height with CVD and cancer suggest that care is required in setting national policies on childhood nutrition lest they have unintended consequences on the incidence of major non-communicable diseases.

Methods All 12 221 participants who consented to an HIV test in a population under continuous demographical surveillance were linked to their homesteads and geo-located in a geographical information system (accuracy of <2 m). We then used a two-dimensional Gaussian kernel of radius 3 km to produce robust estimates of HIV prevalence that vary across continuous geographical space. We also applied a Kulldorff spatial scan statistic (Bernoulli model) to formally identify clusters of infections (P < 0.05).

Results The results reveal considerable geographical variation in local HIV prevalence (range = 6–36%) within this relatively homogenous population and provide clear empirical evidence for the localized clustering of HIV infections. Three high-risk, overlapping spatial clusters [Relative Risk (RR) = 1.34–1.62] were identified by the Kulldorff statistic along the National Road (P ≤ 0.01), whereas three low risk clusters (RR = 0.2–0.38) were identified elsewhere in the study area (P ≤ 0.017).

Conclusions The findings show the existence of several localized HIV epidemics of varying intensity that are partly contained within geographically defined communities. Despite the overall high prevalence of HIV in many rural South African settings, the results support the need for interventions that target socio-geographic spaces (communities) at greatest risk to supplement measures aimed at the general population.

Methods We studied all 84 338 pairs of drivers and front-seat passengers aged ≥18 years in passenger cars involved in traffic crashes with victims recorded in the Spanish traffic crash registry between 2000 and 2004. Relative risks (RR) for the association of age, male sex and non-seat belt use with risk of death were calculated with Poisson conditional and unconditional multiple regression models.

Results For drivers, the risk of death associated with severity of the crash was slightly higher in men (RR = 1.18), and decreased with age (RR = 0.993 per year). However, resilience-dependent risk of death increased with age (RR = 1.028 per year), and especially among unbelted occupants (RR = 4.02).

Conclusions We conclude that in drivers involved in traffic crashes the association of age, sex and seat belt use with risk of death depends on the component of risk considered: severity of the crash or the occupant's resilience to energy.

Methods The National Trauma Survey (NTS) of Rwandans aged 8–19 measured traumatic exposures using an inventory of possible war time experiences and post-traumatic stress reactions with a checklist of symptoms of Post-traumatic stress disorder (PTSD). Individuals meeting assessed PTSD diagnostic criteria are classified as cases of ‘probable PTSD’. The NTS interviewed youth residing in the community and others institutionalized in unaccompanied children's centres; the former (n = 1547) are the subject of the present report. Instrument change midway into the study divides respondents into two samples.

Results Among respondents, over 90% witnessed killings and had their lives threatened; 35% lost immediate family members; 30% witnessed rape or sexual mutilation; 15% hid under corpses. In Sample 1, 95% of respondents reported one or more re-experiencing symptom, 95% reported three or more avoidance/blunting symptoms and 63% reported two or more arousal symptoms; in Sample 2, these figures were 96%, 95% and 56%, respectively. The overall rate of ‘probable PTSD’ was 62% and 54% in Samples 1 and 2, respectively, and exhibited a dose–response relationship with exposure. Among the most heavily exposed individuals the rate was 100%. Rates of ‘probable PTSD’ were higher among females than among males. Results for age were inconsistent.

Conclusion In industrialized societies, most survivors of traumatizing violence experience symptoms only transiently. In the Rwanda survey, symptom levels and rates of ‘probable PTSD’ were exceptionally elevated, suggesting that at the limits of catastrophic man-made violence, psychological resilience among youth is all but extinguished.

Methods A generalized linear Poisson regression model was used to regress a time-series of daily mortality for all-cause and selected causes against temperature, controlling for seasonal and interannual variations, day of week and public holidays. A total of 13 270 all-cause deaths excluding external causes for residents under demographic surveillance in Matlab, Bangladesh were available between January 1994 and December 2002.

Results There was a marked increase in all-cause deaths and deaths due to cardiovascular, respiratory and perinatal causes at low temperatures over a lag of 0–13 days. Every 1°C decrease in mean temperature was associated with a 3.2% (95% CI 0.9–5.5) increase in all-cause mortality. However, there was no clear heat effect on all-cause mortality for any of the lags examined.

Conclusions This study found that daily mortality increased with low temperatures in the preceding weeks, while there was no association found between high temperatures and daily mortality in rural Bangladesh. Preventive measures during low temperatures should be considered especially for young infants.

Methods We examined whether job demands or job control contributed to the socioeconomic gradient in cerebrovascular disease among 48 361 women aged 18–65 years. Job demands, job control and behavioural risk factors were self-reported in 2000–2002; socioeconomic position (as indexed by occupational class) and all of the health measures were obtained from registers. The outcome was recorded hospitalization or death from cerebrovascular disease.

Results During a mean follow-up of 3.4 years, 124 women had a new cerebrovascular disease event. The risk was 2.3 (95% CI 1.3–3.9) times higher among women in low vs high socioeconomic positions. Adjustment for conventional risk factors, such as prevalent hypertension, coronary heart disease, diabetes, smoking, heavy alcohol consumption, physical inactivity and obesity, attenuated this excess risk by 23%. In contrast, adjustment for job demands and job control actually amplified the gradient by 36% suggesting a suppression effect.

Conclusions In this contemporary cohort of employed women, job demands—alone and in combination with job control—suppressed rather than explained socioeconomic differences in cerebrovascular disease.

Methods Using linear regression models that account for serial correlation between months, monthly rotavirus incidence was significantly negatively correlated with temperature, rainfall and relative humidity in 65%, 55% and 60% of studies, respectively. We carried out pooled analyses using a generalized estimating equation (GEE) that accounts for correlation from between-study variation and serial correlation between months within a given study.

Results For every 1°C (1.8°F) increase in mean temperature, 1 cm (0.39 in.) increase in mean monthly rainfall, and 1% increase in relative humidity (22%) this analysis showed reductions in rotavirus incidence of 10% (95% CI: 6–13%), 1% (95% CI: 0–1%), and 3% (95% CI:0–5%), respectively.

Conclusions On the basis of the evidence, we conclude that rotavirus responds to changes in climate in the tropics, with the highest number of infections found at the colder and drier times of the year.

Methods The entire population at-risk aged 16–54 in Nottingham over three time periods (1978–80, 1993–95 and 1997–99) were followed up. All participants presenting with an ICD-9/10 first episode psychosis were included. The remainder of the population at-risk formed the denominator. Standardized incidence rates were calculated at each time period with possible change over time assessed via Poisson regression. We studied six outcomes: substance-induced psychoses, schizophrenia, other non-affective psychoses, manic psychoses, depressive psychoses and all psychotic disorders combined.

Results Three hundred and forty-seven participants with a first episode psychosis during 1.2 million person-years of follow-up over three time periods were identified. The incidence of non-affective or affective psychoses had not changed over time following standardization for age, sex and ethnicity. We observed a linear increase in the incidence of substance-induced psychosis, per annum, over time (incidence rate ratios: 1.15; 95% CI 1.05–1.25). This could not be explained by longitudinal changes in the age, sex and ethnic structure of the population at-risk.

Conclusions Our findings suggest psychotic disorders are not in decline, though there has been a change in the syndromal presentation of non-affective disorders, away from schizophrenia towards other non-affective psychoses. The incidence of substance-induced psychosis has increased, consistent with increases in substance toxicity over time, rather than changes in the prevalence or vulnerability to substance misuse. Increased clinical and popular awareness of substance misuse could also not be excluded.

Background A better understanding of behavioural factors associated with the interruption of human immunodeficiency virus (HIV) dynamics in Uganda are fundamental for guiding HIV prevention strategies. A comparative analysis of population level HIV surveillance and behavioural data in Uganda and countries with similar epidemic dynamics offers a framework to identify distinctive elements of the Ugandan success.

Methods We analysed HIV prevalence among pregnant women attending antenatal surveillance sites between 1990-1998 in Uganda, Kenya, Zambia, and Malawi, and AIDS behavioural data collected in Uganda (1989, 1995), Kenya (1998), Zambia, and Malawi (1996).

Results In Uganda between 1991 and 1998, HIV prevalence rates fell 54% overall, with 75% and 57% declines among 15-19 and 20-24 age groups in urban areas, respectively. HIV declines were associated with a 60% reduction in multiple sexual partners between 1989 and 1995, as well as increased condom use and sexual abstinence. The lack of comparable HIV declines in comparison countries with similar rates of abstinence and condom use, but with multiple sexual partnership rates similar to Uganda in 1989, suggests that partner reduction is paramount in interrupting sexual HIV dynamics. Comparatively, Ugandans were more likely to acknowledge people with AIDS and communicate about HIV through personal networks. Modelling suggests an 80% reduction in incidence among youth early in the 1990s, suggesting a preceding behavioural process during the late 1980s, which reduced HIV risk.

Conclusion The distinctive element explaining declines in HIV prevalence in Uganda is sexual partner reduction. The Ugandan response to AIDS involved a primary HIV intervention whose key outcome was risk avoidance through partner reduction. This focus for HIV prevention could prove more effective than other widely advocated strategies in sub-Saharan Africa.