摘要：Objectives. We sought to identify the income–disability prevalence relationship among older Brazilians. Methods. Data were from 63 985 individuals 60 years and older from the 1998 and 2003 Brazilian National Household Surveys. Generalized additive logistic models with cubic regression splines were used to estimate the disability–income relationships. Results. There was a strong linear relationship between increased income and reduced disability prevalence for most of the income distribution. Benefits were still present above the 90th percentile of income but were more modest. Because incomes among the wealthiest few are disproportionately large, odds ratios of disability nevertheless showed marked improvements, even across the very highest income groups. Conclusions. Among older Brazilians, reduced disability is associated with higher income, and these associations are present even above the 90th percentile of income. In addition to understanding mechanisms of disability reduction among impoverished individuals, work is needed to understand these mechanisms in middle- and high-income groups. Discussions of health inequalities are commonly concerned with poverty. Most empirical research in the field focuses on disadvantage, with relatively little analysis of the role of wealth 1 or higher incomes. Populations worldwide are aging, and there is increasing interest in health inequalities in older populations; however, as with other groups, it is only recently that the effects of middle to higher incomes on aging outcomes have begun to be explored. 2 Many studies have identified associations between lower income and poorer health. 3 In addition, it is clear that the income–health relationship is causal, although the pathways involved are complicated. 4 , 5 It is generally believed that health improvements with increasing income are relatively large but become progressively smaller across the middle and higher end of the income range, yielding a curvilinear relationship. 6 At the cross-national level, for example, a pattern of markedly diminishing improvements in life expectancy is observed when examining mid- to high-range national income countries. 7 Disability (i.e., having difficulty carrying out everyday tasks) is a critical measure of health for societies facing the challenges of caring for increasing numbers of dependent older people. Disability is a strong predictor of needing personal care and of having higher medical costs. 8 , 9 Strong associations between socioeconomic status and disability among older people have been reported in developed countries, 10 – 17 although less is known about patterns in middle-income countries. For Brazil, Melzer and Parahyba 18 , 19 showed that disparities in income and educational attainment are the most important sociodemographic markers associated with differences in disability prevalence in old age. However, the shape of the income disability relationship among older people in Brazil and other developing countries has received little attention. We aimed to estimate the effect of increasing income on disability prevalence in a sample of over 63 000 older people across Brazil. Brazil has extreme income inequalities, and the available nationally representative data provide an opportunity to establish whether reductions in disability prevalence diminish as income increases from middle income through the highest income levels.
