摘要：Objectives. We examined relationships between neighborhood poverty and allostatic load in a low- to moderate-income multiracial urban community. We tested the hypothesis that neighborhood poverty is associated with allostatic load, controlling for household poverty. We also examined the hypotheses that this association was mediated by psychosocial stress and health-related behaviors. Methods. We conducted multilevel analyses using cross-sectional data from a probability sample survey in Detroit, Michigan (n = 919) and the 2000 US Census. The outcome measure was allostatic load. Independent variables included neighborhood and household poverty, psychosocial stress, and health-related behaviors. Covariates included neighborhood and individual demographic characteristics. Results. Neighborhood poverty was positively associated with allostatic load ( P < .05), independent of household poverty and controlling for potential confounders. Relationships between neighborhood poverty were mediated by self-reported neighborhood environment stress but not by health-related behaviors. Conclusions. Neighborhood poverty is associated with wear and tear on physiological systems, and this relationship is mediated through psychosocial stress. These relationships are evident after accounting for household poverty levels. Efforts to promote health equity should focus on neighborhood poverty, associated stressful environmental conditions, and household poverty. A burgeoning literature has demonstrated relationships between socioeconomic status (SES) and a variety of health outcomes. 1–7 The persistence of relationships between SES, assessed at individual or neighborhood levels, and health outcomes over time has led scholars to suggest that SES influences health through a broad range of behavioral and physiological mechanisms. 8–10 Attention has increasingly turned to disentangling the pathways through which SES may influence health, including both individual and neighborhood socioeconomic characteristics. We have contributed to this literature by examining relationships between socioeconomic characteristics of residential neighborhoods and allostatic load, an indicator of cumulative physiological response to stress. We examined potential pathways linking neighborhood SES to allostatic load by testing the extent to which these relationships are mediated by perceived or self-reported indicators of psychosocial stress and by health-related behaviors. The conceptual model that guides this analysis builds on both conceptual and empirical research arguing that SES is a fundamental factor that influences health through multiple pathways, 8,9,11,12 with cumulative health effects over the life course. Neighborhood poverty levels influence local social and physical environmental conditions (e.g., access to food, safe places for physical activity), 12 which influence health-related behaviors (e.g., dietary practices, physical activity). Conditions in the social and physical environment may also influence health if they are conducive to stress and are referred to as stressors if they are likely to be perceived as harmful, threatening, or bothersome 13 or as placing a demand on individuals that results in a physiological adaptational responses. 14 Physiological responses are initiated as the body attempts to achieve stability (allostasis) when exposed to chronically stressful physical and social environments, for example, chronic challenges experienced as a result of poverty. 15–23 Physiological responses to stress can accumulate and result in overexposure to neural, endocrine, and immune stress mediators (allostatic load), leading to enduring negative health outcomes through effects on the hypothalamic–pituitary–adrenal cortex, sympathetic nervous system, and immune system, with subsequent implications for peripheral biology. 16,20,24–31 Negative health outcomes include effects on systolic and diastolic blood pressure, which are associated with higher mortality rates, cardiovascular disease, stroke, and the loss of physical and cognitive functioning. 32–35 Chronic exposures to stress also affect metabolic systems, with established implications for health, including higher total cholesterol, lower high-density lipoproteins, higher weight, 30,36–39 and elevated glucose levels. 30,40–43 These metabolic indicators have been associated with heightened risk of mortality, increased cardiovascular risk, and poorer cognitive functioning. 30,32,44–46 McEwen et al. 29,30 conceptualized allostatic load as an indicator of the “cumulative physiological toll on multiple major biological systems over the life course” 30 (p223) that results from exposure to stressful life circumstances. Substantial evidence suggests that cardiovascular and metabolic risk varies by individual- or household-level SES, and recent studies have specifically demonstrated an inverse socioeconomic gradient in allostatic load. 30,47–49 A growing body of research 1–7 also demonstrates relationships between neighborhood SES and a variety of health outcomes, independent of the effects of individual or household income. Merkin et al. 50 tested whether associations between percentage of households below the poverty line at the census tract level and allostatic load differed by race/ethnicity, using a nationally representative sample of non-Hispanic White, non-Hispanic Black, and Mexican Americans (National Health and Nutrition Examination Survey [NHANES] 1988–1994). They reported a significant inverse relationship between neighborhood SES and allostatic load among non-Hispanic Blacks, with similar but not significant trends among non-Hispanic Whites and Mexican Americans. Stimpson et al., 51 using data from NHANES III, found a positive association between a composite measure of neighborhood deprivation and serum triglyceride levels, 1 component of allostatic load. Building on this conceptual model and empirical literature, we examined 3 major research questions ( Figure 1 ). First, we asked whether neighborhood poverty is associated with allostatic load among non-Hispanic Black, non-Hispanic White, and Hispanic residents of a major Midwestern urban community, independent of the effects of household income. Second, we tested specific pathways through which neighborhood poverty may contribute to allostatic load. Specifically, we tested the hypothesis that relationships between neighborhood poverty and allostatic load are mediated by self-reported psychosocial stress associated with neighborhood conditions. To examine the specificity of mediating effects, we tested the extent to which relationships between neighborhood poverty and allostatic load are mediated by indicators of psychosocial stress that reflect domains other than neighborhood environments, for example, experiences of unfair treatment. 52,53 Third, because numerous health-related behaviors have been found to be associated with neighborhood poverty, including dietary patterns, 54–56 smoking, 57–59 physical activity, 51,59–61 and alcohol use, 51,62 and these behaviors may also be associated with components of allostatic load (e.g., blood pressure, lipid levels), we examined the extent to which relationships between neighborhood poverty and allostatic load are mediated by health-related behaviors. Open in a separate window FIGURE 1— Hypothesized pathways mediating relationships between neighborhood poverty and allostatic load: Healthy Environments Partnership Community Survey, Detroit, MI, 2002–2003.
