Variation in health inequalities according to measures of socioeconomic status and age

Objective: To examine variation in the magnitude of socioeconomic inequalities in health and age-related variations in inequalities, according to the socioeconomic status (SES) measure used. Methods: Cross-sectional study involving 205,709 participants in the 45 and Up Study. We used the Relative Index of Inequality (RII) to quantify health inequalities in relation to income, education and Socio-Economic Indexes for Areas (SEIFA). The outcomes used were heart disease and self-rated health. Analyses were stratified by age (45-64, 65-79, >= 80 years). Results: RIIs were largest for income and smallest for SEIFA; they were generally largest in the youngest age group and smallest in the oldest group. Age-related differences in RIIs were particularly marked for income (e. g. for fair/poor health, RII= 11.81, 95% CI 11.14-12.53 in the 45-64 age group and RII= 2.42, 95% CI 2.10-2.78 in >= 80 group), and less marked for SEIFA (e. g. respectively, RII= 2.68, 95% CI 2.53-2.84 and RII= 1.32, 95% CI 1.22-1.44). Conclusions: The magnitude of socioeconomic inequality in health varies substantially according to the type of SES measure used and age. Income is the most sensitive measure. Implications: Researchers and policy makers should be aware of the extent to which SEIFA-based estimates underestimate the magnitude of health inequality compared to individual-level measures, especially in younger age groups.