摘要：State-level income inequality has been found to have an effect on individual health outcomes, even when controlled for important individual-level variables such as income, education, age, and gender. The effect of income inequality on health may not be immediate and may, in fact, have a substantial lag time between exposure to inequality and eventual health outcome. We used the 2006 American Community Survey to examine the association of state-level income inequality and 2 types of physical disabilities. We used 6 different lag times, ranging between 0 and 25 years, on the total sample and on those who resided in their state of birth. Income inequality in 1986 had the strongest correlation with 2006 disability levels. Odds ratios were consistently 10% higher for those born in the same state compared withthe total population. In the United States, studies using multilevel statistical techniques have found a relation between state-level income inequality and individual health outcomes, including self-reported health 1 , 2 and limitations in activities of daily living (ADLs). 3 This relation remained even when important individual-level variables such as income, education, age, and gender, were controlled for in the analysis. The majority of studies on the income inequality–health relation have used current measures of both inequality and health. The 3 proposed mechanisms through which income inequality could affect individual health are as follows: systematic underinvestment in a wide range of health and social infrastructure, 4 , 5 unfavorable social comparison, 6 , 7 and lower levels of social cohesion and social capital. 8 Each of these potential mechanisms suggests the effect of income inequality on health would not be immediate and may, in fact, have a substantial lag time between exposure to inequality and eventual health outcome. A few multilevel studies that have examined the “lag effect” of income inequality on individual health outcomes 9 – 11 have suggested that self-reported health was more strongly associated with income inequality from 15 years previous than from shorter or longer time lags. There is a clear need for additional use of multilevel modeling to explore individual health outcomes other than self-reported health and to consider outcomes at time periods other than the late 1990s 10 , 12 and different sources of data. Furthermore, all of these studies were limited by potential misclassification of exposure because they did not control for movements between states during the lag time period. 9 Finally, these studies were based on the Current Population Survey, 13 which does not include individuals in nursing homes and other institutions, who represent a significant portion of the seriously ill in this country. To address these concerns, we used multilevel analysis techniques to examine the association of state-level income inequality and 2 types of disabilities measured in 2006 using 6 different lag times ranging between 0 and 25 years. Disability is an excellent predictor of medical and social service need, and it greatly influences quality of life and productivity. 14
