Incidence of ischaemic stroke according to income level among older people: the 3C study

Background: stroke has been shown to follow a social gradient with incidence rising as socioeconomic status decreases. Objective: to examine the relationship between socioeconomic status and ischaemic stroke risk amongst older people. Setting: the Cities of Bordeaux, Dijon and Montpellier in France. Subjects and methods: nine thousand and two hundred and ninety-four non-institutionalised persons aged 65 years or more followed for 6 years. Results: the distribution of cardiovascular risks factors was consistent with the classical finding of more favourable risk profiles among the advantaged socioeconomic groups. One hundred and thirty-six individuals developed a first ever ischaemic stroke (incidence rate: 3.2 per 1,000 py (person-years), 95% CI 2.7-3.8). The age-and sex-adjusted incidence of ischaemic stroke increased with increasing level of income (from 2.4 to 4.1 per 1,000 py, P = 0.04). In the multivariable analysis adjusting for cardiovascular risk factors, the higher income group displayed a 80% increased risk of ischaemic stroke compared with less wealthy participants (hazards ratio 1.77, 95% CI 1.20-2.61). Conclusions: in this community-based sample of older individuals, a higher level of household income was associated with a higher risk of ischaemic stroke, a reversal of the social gradient usually reported in younger age groups. Selective survival is one of the potential explanations for this unexpected finding.