Income differences in cardiovascular disease: is the contribution from work similar in prevalence versus mortality outcomes?

The objective of this research is to study the contribution of adverse working conditions to the association between income and cardiovascular disease (CVD), and to analyze differences across prevalence and mortality outcomes. Cross-sectional data from the Swedish Surveys of Living Conditions, 1996-1999 (N = 6,405), and longitudinal registry data for the period 1990-95 (10,916 CVD deaths) were used, including employed wage earners, aged 40-64. Working conditions were assessed through self-reports and imputed from a job exposure matrix, respectively. Multiple logistic and Poisson regressions were applied. There were strong associations between income and CVD. Those in the lowest income quartile had 3.6 (prevalence) and 2.1 (mortality) times higher risk of CVD, compared to those in the highest income quartile (with a gradient for the intermediate groups). In the survey, low job control and physical demands contributed 8-10% to the association between income and CVD prevalence. This contribution was 10% for low job control in the mortality follow-up. A small proportion of the association between income and the prevalence of or mortality from CVD is attributable to working conditions.