Using self-rated health for analysing social inequalities in health: a risk for underestimating the gap between socioeconomic groups?

Background: The use of self-rated health (SRH) for measuring health inequalities could present some limits. The impact of the same disease on SRH could be different according to health expectations people have which are associated with social characteristics. The aim of this study was to analyse the link between physical health status and SRH, according to level of education. Method: Data from the National Health and Nutrition Examination Survey for the years 2001-4 were used. Multivariate logistic regression analyses were performed for assessing the relation between health status and SRH according to educational level. Results: The sample consisted of 4661 men and 4593 women. Reporting functional limitation was associated more strongly with poor SRH in higher educated women than in lower educated women (OR, 8.73, 95% CI 5.87 to 12.98 vs OR, 3.97, 95% CI 2.93 to 5.38 respectively), as was reporting respiratory disease (OR, 5.17, 95% CI 3.67 to 7.30 vs OR, 2.60, 95% CI 1.72 to 3.95 respectively), cardiovascular disease (OR, 9.79, 95% CI 6.22 to 15.40 vs OR, 3.34, 95% CI 2.29 to 4.87 respectively) and dental problems (OR, 4.37, 95% CI 3.22 to 5.92 vs OR, 2.58, 95% CI 1.97 to 3.39 respectively). Reporting functional limitation was associated more strongly with poor SRH in higher educated men than in lower educated men (OR, 7.71, 95% CI 5.04 to 11.79 vs OR, 4.87, 95% CI 3.30 to 7.18 respectively), as reporting oral problems (OR, 2.62, 95% CI 1.84 to 3.74 vs OR, 3.63, 95% CI 2.81 to 4.68 respectively). Conclusions: The impact of health problems on SRH is stronger among better educated individuals. This phenomenon could lead to an underestimate of the health inequalities across socioeconomic groups.