controls were possible with exactly equivalent socioeconomic measures is not known.

MECHANISMS

Socioeconomic status affects health through a variety of mechanisms, including psychosocial factors, health behaviors, and health care (Anderson, 1995; Hummer et al., 1998; Kington and Nickens, 2001; Seeman and Crimmins, 2001). In general, persons of higher socioeconomic status are less exposed to health-threatening conditions and have more resources to buffer health threats. For instance, persons with more education have greater ability to self-monitor and manage highly effective but complicated therapies for such conditions as diabetes and HIV (Goldman and Smith, 2002). Variation in this ability may involve other factors in addition to education, however. In general, the intervening mechanisms that have been studied through which socioeconomic status affects health—such as behavior risk factors (Lantz et al., 2001)—do not entirely account for the effects of socioeconomic status, leaving much of these effects still to be explained. In addition, these intervening mechanisms could operate independently of socioeconomic status.

Additional factors may also obscure the effects of status. For instance, recent immigrants often have lower incomes, at least initially, but enjoy health advantages for other reasons. Working-age immigrants, particularly those with employment visas or who enter as spouses of U.S. citizens, appear to be strongly selected for health (Jasso et al., 2004). Assessing the role of socioeconomic factors in group health, therefore, requires attention to health in countries of origin and to the average healthiness of the original immigrants, the diversity in health status among them, and their subsequent health trajectories over their lifetimes and those of their descendants.

In addition to these individual-level mechanisms, considerable research in the last decade argues that macrolevel socioeconomic factors affect individual health outcomes (Marmot, 2000; Wilkinson, 1997). One form of the hypothesis is that inequality, as measured in various ways, has a negative effect on individual health outcomes, especially for those at the bottom of the social and economic hierarchy. In this view, the cumulative stress of being at the bottom of the hierarchy eventually takes a toll in poorer health. This is an important scientific hypothesis with far-reaching implications. However, much of the influential early work on this subject suffered from severe limitations, including inadequate conceptualization of and difficulties in separating individual from macrolevel influences. Recent work by Deaton and Paxson (2001) argues that, at least for U.S. blacks and whites, the evidence that rising levels of income inequality have negative health consequences is dubious.



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