Characteristics associated with self-rated health in the CARDIA study: Contextualising health determinants by income group.

An understanding of factors influencing health in socioeconomic groups is required to reduce health inequalities. This study investigated combinations of health determinants associated with self-rated health (SRH), and their relative importance, in income-based groups. Cross-sectional data from year 15 (2000 - 2001) of the CARDIA study (Coronary Artery Risk Development in Young Adults, USA) - 3648 men and women (mean 40 years) - were split into 5 income-based groups. SRH responses were categorized as 'higher'/'lower'. Health determinants (medical, lifestyle, and social factors, living conditions) associated with SRH in each group were analyzed using classification tree analysis (CTA). Income and SRH were positively associated (p < 0.05). Data suggested an income-based gradient for lifestyle/medical/social factors/living conditions. Profiles, and relative importance ranking, of multi-domain health determinants, in relation to SRH, differed by income group. The highest ranking variable for each income group was chronic burden-personal health problem (<$25,000); physical activity ($25-50,000; $50-75,000; $100,000 +); and cigarettes/day ($75-100,000). In lower income groups, more risk factors and chronic burden indicators were associated with SRH. Social support, control over life, optimism, and resources for paying for basics/medical care/health insurance were greater (%) with higher income. SRH is a multidimensional measure; CTA is useful for contextualizing risk factors in relation to health status. Findings suggest that for lower income groups, addressing contributors to chronic burden is important alongside lifestyle/medical factors. In a proportionate universalism context, in addition to differences in intensity of public health action across the socioeconomic gradient, differences in the type of interventions to improve SRH may also be important.