Our analyses lead to two important conclusions. One, the exclusion of neighborhood context leads to upwardly biased estimates of racial health disparities that were believed to be independent of socioeconomic conditions. As a consequence—our second conclusion is that accounting for place provides further explanation for a moderately large portion of observed racial health disparities. The contribution of neighborhood context to the observed racial health gap varies considerably by age and gender, but is substantively and statistically significant across a host of models that control for both overweight status and activity limitations and models that do not. In short, place explains a significant proportion of racial disparities in health that were previously unaccounted for by individual-level SES.
The observation that place explains a larger proportion of the racial health gap explained in younger age groups is consistent with results from studies that found larger neighborhood associations for younger adults and non-significant associations for older adults (e.g., Kling, Liebman, Lawrence, & Sanbonmatsu, 2004
; Chaix, Rosvall & Merlo, 2007
). A possible explanation for the pattern is that the health of young adults is relatively robust and less likely to be influenced by individual-level SES. Consequently, variation in external factors such as environmental exposures (e.g., exposure to toxins), built environment (e.g., availability of safe recreational facilities), and social conditions (e.g., exposure to neighborhood violence and drugs) may play a greater role in contributing to the health differences between blacks and whites at younger ages. At older ages, health level and health care may depend more on personal socioeconomic resources that have already been accounted for in the models. Another possible reason is that the current neighborhood conditions fail to capture the life-long residential context that resulted in the cumulative health disadvantage experienced by blacks (as supported by the increasing health gap by age) and thus are less likely to explain health difference at older ages. That is, because current residential context is likely to be more representative of long-term neighborhood conditions for younger age groups due to their limited total exposure to neighborhood characteristics and to be less reliable as an indicator of average exposure for older adults, we would expect the underestimation of place effects to be more severe at older ages than at younger ages. Finally, just as socio-economic disparities decrease over the life-course due to selective mortality, we might expect the same to happen with respect to the effect of current residential context.
Our finding that residential context explains less of the racial health disparities among women than among men is related to other studies that have found differential neighborhood associations in health across gender. Molinari, Ahern, & Hendryx (1998)
found that women's health is more strongly associated with community problems (e.g., crime, poverty, domestic violence), while environmental problems (e.g., quality of outdoor air, drinking water, trash disposal) seem to be associated with men more than women. Other studies have found stronger neighborhood connections with SRH for women than for men (Stafford et al., 2005
; Kavanagh, Bentley, Turrell, Broom, & Subramanian, 2006
) and differential neighborhood associations with weight outcomes across gender (Robert & Reither, 2004
; Chang & Christakis, 2005
; Wang et al., 2007
). In fact, much of the literature on neighborhood context indicates that women are more influenced by some aspects of neighborhood context than are men and that the patterns vary considerably across health outcomes (Bird & Rieker, In Press
). Here however, we are focused not on whether men or women are more affected by neighborhood context, but specifically on whether place explains more of the racial gap in SRH for women than for men.
The finding that more of the racial gap in health is explained by context for men than for women is consistent with greater geographic variation in black men's opportunities for a healthy life relative to those of white men than among black women relative to white women. For example, the risk of unemployment and exposure to violence likely are higher for black men than for white men and for women of either race (Bird & Rieker, In Press
). As such, the patterning of these types of risk across neighborhoods and the contribution of place may be much stronger for black men. Consequently, our results suggest that understanding and addressing place effects may be particularly important to improving the health of black males.
Overall, our results suggest that neighborhood context per se explains a moderate to substantial portion of the black/white health gap, net of individual characteristics. To summarize, residential context might account for as much as 76 percent of the residual black/white disparities in health among 25-year-old males, but in contrast, only accounts for about 15 percent of the residual black/white disparities among older women. Although the range of the findings is rather wide, it nonetheless indicates that place may be associated with a non-inconsequential portion of the racial health gap. It is unclear whether our results would generalize to other countries. Nonetheless, this study takes an important, albeit limited, step toward quantifying this potential contribution as few attempts have been made to quantify the actual role that residential context plays in producing racial health disparities.
Limitations to our analyses include the assumption that VSA-level effects are equal across residents within the same VSA, an unlikely reality given that stressful environments might have larger effects on the unemployed, for example. Another is the pooling of data across a number of years to ensure large enough numbers of respondents in each VSA to produce stable estimates. As a result, respondents in the same VSA may not have actually lived there concurrently, and the characteristics of the VSA may have changed dramatically over time—a change that we are unable to measure. This is unlikely, however, as analyses of census data indicate that neighborhoods do not usually change dramatically within a small time period.
Importantly, several factors may bias our results in either direction. These findings may have overestimated the contribution of neighborhoods to racial health disparities if omitted variables at the individual-level are correlated with both race and VSA characteristics and/or included individual-characteristics were poorly measured or misspecified. VSA indicators would absorb all the unmeasured or poorly measured compositional differences across VSAs, erroneously attributing them to contextual effects. Income, for example, is often believed to be poorly measured. Consequently, the VSA fixed effects may be absorbing some of the measurement noise and model misspecification in personal income. Though these factors are not problematic with respect to further explaining the black/white health gap and reducing the race residual per se, it is of sizable consequence to what inferences can be made of the sources that led to the increased explanation of the black health disadvantage. However, this problem is not unique to our FE strategy and the difficulty of disentangling composition versus context is a common problem in neighborhood-effect studies.
Still, there are reasons to suspect that these estimates might be biased downwards (i.e., they under-report neighborhood contribution to health disparities). First, place effects on health most likely manifest themselves as early as birth (O'Campo, Xue, Wang, & Caughy, 1997
), accumulating and persisting through adolescence (Brooks-Gunn, Duncan, & Aber, 1997
) and into old age (Yen & Kaplan, 1999b
). Models relying on a single point-in-time estimate of current residential context cannot distinguish between individuals with long-time exposures to disadvantaged neighborhoods from individuals with only a limited exposure.
Second, the effects of residential context might be felt much more broadly than at the level in which VSAs are measured. That is, while this small area might capture much larger variation in the social and built environment in neighborhoods than census tracts do, both extra-residential variation and spill-over from neighboring places might have both direct and indirect effects on health that are not captured by such a circumscribed measurement of social and physical space. In fact, recent evidence suggests that failure to control for extra-residential characteristics (in terms of the characteristics of the social space that individuals occupy outside of their homes, such as places of work, worship, shopping, and play) might actually suppress the true effects of residential context on health (Inagami, Cohen, & Finch, 2005
Third, not all place effects on health work directly through health-related mechanisms. Place might indirectly affect health by affecting an individual's access to quality education, jobs, and higher levels of income (Wilson, 1996
)—all factors that have been associated with innumerable health outcomes (Link & Phelan, 1995
). As such, controlling for these variables represents at least a partial over-control for potential place effects and may affect how much of the variation in health disparities is actually attributable to residential context. For these reasons, we believe our estimates to be fairly conservative, or downwardly biased estimates of the role of residential context in contributing to racial health disparities.
In conclusion, although this paper has made a substantial attempt at quantifying the role of residential context in generating racial disparities in health, much research remains to be done. First, attempts to quantify the contribution of place should continue, particularly in view of the limitations inherent in the use of the NHIS data set. Second, explanations for why place effects on health might diminish over the life course, or at least their ability to explain disparities, need to be explored. Third, the notion that residential context explains less of the racial disparity among women than among men is worthy of both empirical and theoretical focus. Finally, and most importantly, the precise factors that contribute to racial disparities in health need to be continually generated by careful empirical research, much needed theory, and attention to the methodological shortcomings of so-called “neighborhood effects” studies.