Ours is the first large-scale prospective study of the influence of neighborhood characteristics on weight gain among African American women. The findings, based on approximately 48,000 African American women followed for 10 years, indicate that both weight gain and incidence of obesity were inversely associated with the socioeconomic level of the neighborhoods in which women resided, above and beyond the effects of individual SES and behavioral factors such as physical activity and caloric intake. The associations with neighborhood SES were most apparent among the most well educated women.
A longitudinal analysis carried out in the Atherosclerosis Risk in Communities study used a factor score based on 6 US census variables that included 5 of the 6 variables in our score. Contrary to our findings, mean 5-year weight gain was greatest among African American women in the highest SES neighborhoods. A possible explanation for the different findings lies in the characteristics of the study participants. In the Atherosclerosis Risk in Communities study, 40% of the black women had not completed high school[12
], compared with 3% of BWHS participants. These are the women who have the least favorable health behaviors (e.g. poor diet, sedentary)[27
] and may therefore be least affected by neighborhood characteristics. In the present study, low neighborhood SES was not associated with increased weight gain among the subgroup of women who had completed 12 or fewer years of education.
As noted in the introduction, cross-sectional studies have found positive associations of obesity with low neighborhood SES.[5
] Only the report from NHANES (which included 3203 black men and women) presented race- and sex-specific analyses.[13
] In that study, black women who lived in neighborhoods characterized as the most deprived had higher levels of BMI than those in less deprived neighborhoods, independent of individual education and family income.[13
] No U.S. studies have assessed the association within strata of education.
A potential biologic mechanism linking BMI and neighborhood SES may be stress. Neighborhoods of low SES are sources of chronic stress due to limited access to resources like high-quality housing and health care, high crime rates and perceived threats of crime, more refused services (e.g., taxi, credit), and greater crowding and exposure to noise.[16
] Stress can result in neuroendocrine-autonomic dysregulation which in turn can influence the accumulation of excess body fat.[17
] Stress activates the central sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis which, via corticotrophin-releasing hormone, stimulates adrenocorticotropic hormone production and thereby cortisol secretions.[29
] Cortisol activates lipoprotein lipase, which regulates lipid accumulation in adipocytes, increasing fat retention.[17
] Nonbiologic mechanisms include limited access in disadvantaged neighborhoods to healthy foods[14
] and exercise facilities.[15
Follow-up studies such as our own improve upon cross-sectional studies by assessing the relation of neighborhood SES to weight change and obesity incidence over time. In cross-sectional studies, some portion of associations observed between neighborhood characteristics and BMI may be due to selection bias, wherein overweight and obese people are preferentially selected into neighborhoods of low SES due to lack of choices in residential location.
A validation study indicated that reporting of weight by BWHS participants was accurate.[25
] Errors in reporting weight, if nondifferential, would have diluted associations. We were able to control for important potential confounding variables, including physical activity, caloric intake, cigarette smoking, and individual level of SES.
A study limitation is that we assessed only those neighborhood factors thought to characterize socioeconomic aspects of a residential neighborhood. We were not able to assess other neighborhood factors such as psychosocial hazards[11
], the built environment[30
], or food sources.[31
The large size of the BWHS and the substantial number of well-educated African American women participants allowed for informative analyses of the modifying effect of education on the association of neighborhood SES with weight gain and obesity. Our results indicate that well educated African American women who live in disadvantaged neighborhoods have greater weight gain and are more likely to develop obesity than African American women of the same educational levels who live in more affluent neighborhoods. Thus, neighborhood SES may contribute to the black-white disparity in obesity, given that far more well-educated black women live in disadvantaged neighborhoods than do similarly-educated white women.[7
] Our findings contribute to the growing body of evidence that implicates aspects of neighborhood as causes of adverse health outcomes, and as contributing to population disparities in health.[32
What is already known on this subject
Studies from the U.S. and Europe show that women living in neighborhoods of low socioeconomic status (SES) have higher body mass indices (BMI) than do women living in neighborhoods of higher SES, regardless of individual SES. Most previous studies have been cross-sectional and results may reflect residential selection bias. Prospective data on the relation between neighborhood SES and BMI and weight change are needed, particularly among African-American women among whom the prevalence of overweight and obesity is high and who, regardless of their individual SES, are more likely to live in disadvantaged neighborhoods than are white women.
What this study adds
Among 48,000 African American women followed for 10 years, both weight gain and incidence of obesity were inversely associated with the SES of the neighborhoods in which the women resided, above and beyond the effects of individual SES, physical activity, and caloric intake. Our findings suggest that living in neighborhoods of lower SES contributes to overweight and obesity in African American women.