IJE Advance Access originally published online on October 19, 2008
International Journal of Epidemiology 2008 37(6):1439-1440; doi:10.1093/ije/dyn208
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Letters to the Editor |
Author's Response
1 INSERM U687, Hôpital Paul Brousse, Bâtiment 15/16, 94807 Villejuif Cedex, France.
2 Department of Epidemiology & Public Health, University College London, London, WC1E 6BT, UK.
* Corresponding author. INSERM U687, Hôpital Paul Brousse, Bâtiment 15/16, 16 avenue Paul Vaillant Couturier, 94807 Villejuif Cedex, France. E-mail: Archana.Singh-Manoux{at}inserm.fr
We thank SV Subramanian and Karen Ertel1 for their letter regarding our paper on the association between self-rated health (SRH) and mortality.2 We agree with them that testing whether the SRH and mortality association varies by socioeconomic position (SEP) provides only indirect clues as to whether the use of SRH instead of a more ‘objective’ measure of health under- or over-estimates social inequalities in health. However, the primary purpose of our paper, and the two others published alongside,3,4 was to examine whether markers of SEP moderate the association between SRH and mortality. The Idler and Benyamini review of 27 papers on the association between SRH and mortality suggested a stronger association in men compared with women;5 more recent work adds age as another moderator of the association between SRH and mortality.6 SRH is an important research tool, allowing a simple question to monitor population health. This makes it important to identify conditions under which the association with mortality ‘strengthens, weakens, or disappears’.6
Previous research suggested no moderating effect for SEP7,8 but all three papers show SEP to moderate the association between SRH and mortality.2–4 Our results are different to those reported in the other two papers, our analysis shows SRH to be less predictive of mortality in the high SEP groups. However, these results were robust as we examined whether the results held using SRH as a continuous variable and estimated differences in absolute risk. Clearly, further research is required to understand the discrepancy in the results and thereby the role played by SEP in shaping the association between SRH and mortality. One element that needs further attention is age, as the SRH mortality association has been shown to weaken with age.6 Our analysis was based on individuals aged 35 to 50 at baseline followed up for 17 years; the other studies were on those aged 25–74 years (follow-up 13 years)3 and 25–99 years at baseline (follow-up 11 years).4 Thus, there are clear differences in the age-groups examined in the three papers.
Even though the implication of our analysis for social inequalities research using SRH was not the key focus of our paper, the points raised by Subramanian and Ertel are important. The dissonance between self-reported health and mortality has been discussed previously by Sen. In interstate comparisons using Indian data he observed that states with highest life expectancy also have highest self-reported morbidities.9 Further research is required to examine whether these discrepancies are context dependent and explore the reasons behind them. Here, we replicate the analyses of Subramanian and Ertel in the GAZEL cohort with the three markers of SEP used in our paper, see Table 1. The outcomes used are mortality till 2001, a follow-up of 12 years similar to the Established Populations for Epidemiologic Studies of the Elderly (EPESE) data and SRH in 2001. The mean age of participants at baseline was 44.2 (SD 3.5) years, considerably younger than the EPESE elderly. The results for education suggest that using SRH instead of mortality underestimates social inequalities. However, this does not appear to be the case for occupational position or income. In general terms, SRH is a simple, inexpensive and quite an accurate measure of health. Nevertheless, the social patterning of discrepancies between objective and subjective measures of health is important as it might provide clues as to the range of information used by people to rate their own health.
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References
1 Subramanian SV, Ertel K. Is the use of self-rated health measures to assess health functioning misleading? Int J Epidemiol (2008) 37:1436–37.
2 Singh-Manoux A, Dugravot A, Shipley MJ, et al. The association between self-rated health and mortality in different socioeconomic groups in the GAZEL cohort study. Int J Epidemiol (2007) 36:1222–28.
3 Huisman M, Lenthe FV, Mackenbach J. The predictive ability of self-assessed health for mortality in different educational groups. Int J Epidemiol (2007) 36:1207–13.
4 Dowd JB, Zajacova A. Does the predictive power of self-rated health for subsequent mortality risk vary by socioeconomic status in the US? Int J Epidemiol (2007) 36:1214–21.
5 Idler EL, Benyamini Y. Self-rated health and mortality: a review of twenty-seven community studies. J Health Soc Behav (1997) 38:21–37.[CrossRef][Web of Science][Medline]
6 Helweg-Larsen M, Kjoller M, Thoning H. Do age and social relations moderate the relationship between self-rated health and mortality among adult Danes? Soc Sci Med (2003) 57:1237–47.[CrossRef][Web of Science][Medline]
7 Burstrom B, Fredlund P. Self rated health: is it as good a predictor of subsequent mortality among adults in lower as well as in higher social classes? J Epidemiol Community Health (2001) 55:836–40.
8 Van Doorslaer E, Gerdtham UG. Does inequality in self-assessed health predict inequality in survival by income? Evidence from Swedish data. Soc Sci Med (2003) 57:1621–29.[CrossRef][Web of Science][Medline]
9 Sen A. Health: perception versus observation. Br Med J (2002) 324:860–61.
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