IJE Advance Access originally published online on January 6, 2008
International Journal of Epidemiology 2008 37(3):615-624; doi:10.1093/ije/dym250
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Educational attainment and cigarette smoking: a causal association?
1Department of Society, Human Development, and Health, Harvard School of Public Health, Boston, MA, USA.
2Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
3Child Trends, Washington, DC, USA.
4Office of Behavioral and Social Science Research, National Institutes of Health, Bethesda, MD, USA.
5Department of Psychiatry and Department of Epidemiology, McGill University, Montreal, Canada.
6Department of Psychiatry and Human Behavior, Brown Medical School and Butler Hospital, Providence, RI, USA.
7Department of Community Health, Brown University, Providence, RI, USA.
*Corresponding author. Department of Society, Human Development, and Health, 677 Huntington Avenue, Boston, MA 02115, USA. E-mail: sgilman{at}hsph.harvard.edu
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Abstract |
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Background Despite abundant evidence that lower education is associated with a higher risk of smoking, whether the association is causal has not been convincingly established.
Methods We investigated the association between education and lifetime smoking patterns in a birth cohort established in 1959 and followed through adulthood (n = 1311). We controlled for a wide range of potential confounders that were measured prior to school entry, and also estimated sibling fixed effects models to control for unmeasured familial vulnerability to smoking.
Results In the full sample of participants, regression analyses adjusting for multiple childhood factors (including socioeconomic status, IQ, behavioural problems, and medical conditions) indicated that the number of pack-years smoked was higher among individuals with less than high school education [rate ratio (RR) = 1.58, confidence interval (CI) = 1.31, 1.91]. However, in the sibling fixed effects analysis the RR was 1.23 (CI = 0.80, 1.93). Similarly, adjusted models estimated in the full sample showed that individuals with less than high school education had fewer short-term (RR = 0.40; CI = 0.23, 0.69) and long-term (RR = 0.59; CI = 0.42, 0.83) quit attempts, and were less likely to quit smoking (odds ratio = 0.34; CI = 0.19, 0.62). The effects of education on quitting smoking were attenuated in the sibling fixed effects models that controlled for familial vulnerability to smoking.
Conclusions A substantial portion of the education differential in smoking that has been repeatedly observed is attributable to factors shared by siblings that contribute to shortened educational careers and to lifetime smoking trajectories. Reducing disparities in cigarette smoking, including educational disparities, may therefore require approaches that focus on factors early in life that influence smoking risk over the adult life span.
Keywords Education, smoking, causality, disparities
A previous version of this work was presented at the Society for Epidemiologic Research/North American Congress of Epidemiology, June 2006, Seattle, WA, USA. Accepted 28 November 2007