The overall goal of our study was to investigate individual-level and neighborhood-level chronic stressors as potential mechanisms contributing to race/ethnic differences in blood pressure. Racial/ethnic disparities in hypertension prevalence have been previously reported in the MESA cohort with African Americans having a higher prevalence of hypertension than whites or Hispanics in the full MESA sample.(34
) However, in this subsample restricted to three of the MESA sites (including NY were Hispanics were predominately Caribbean-origin) we also found that the prevalence of hypertension was higher in Hispanics as compared to whites. This is contrary to nationally representative data sources such as the National Health and Nutrition Examination Survey, (35
) that include Hispanics of predominately Mexican origin.
We found that African Americans reported more perceived major and everyday discrimination than whites and Hispanics. In addition, African Americans and Hispanics lived in more stressful neighborhoods than whites and higher levels of neighborhood stressors in turn were associated with a higher prevalence of hypertension, independent of site, age, and gender. We also documented a substantial reduction in the association between race/ethnicity and hypertension after adjustment for neighborhood-level stressors.
This study is novel in extending the study of psychosocial stressors and hypertension to the neighborhood level. This is one of the first studies to measure associations between neighborhood stressors and blood pressure by moving beyond census derived indicators of neighborhood socioeconomic position to the direct measurement of neighborhood conditions. We previously examined a range of physical (walkability, availability of healthy foods) and social features (safety, social cohesion), of neighborhood environments in relation to hypertension and documented associations between these features and HTN, independent of some individual-level factors (age, gender, education, income). In current analyses we found that neighborhood stressors were also associated with hypertension, although possibly due to the strong patterning of neighborhood characteristics by race/ethnicity, these associations were not statistically significant after adjusting for race/ethnicity. However, our trend of positive associations between neighborhood stressors and the prevalence of hypertension, is consistent with prior work showing significantly higher systolic and diastolic blood pressure for black men and women living in high stress areas (as characterized by census measures) compared to black men and women in low stress areas, after adjustment for a series of individual-level variables (such as age and socioeconomic position). (23
Our study is also one of few that attempt to examine the contribution of stressors to race/ethnic disparities in hypertension and related outcomes (16–18).
The fact that race/ethnic differences in hypertension were reduced after adjusting for neighborhood stressors is compatible with (although it does not categorically demonstrate) a causal role of neighborhood stressors in creating the observed disparities in hypertension prevalence. (37
) The proportion of race/ethnic differences in hypertension prevalence that is statistically explained by neighborhood stressors may differ from sample to sample depending on the degree of residential segregation and the strength of associations between neighborhood characteristics and hypertension; hence we do not draw inferences regarding the percent of the difference “explained”. In addition, because of the potential for many unobserved social and biologic differences between race/ethnic groups which are not accounted for by the variables we included, we make no attempt to interpret the determinants of the race/ethnic difference that persists after adjustment.(38
Although, we provide a more complete assessment of chronic stressors operating at different levels than prior work, we have not considered the full spectrum of stressors that individuals are exposed to throughout the lifecourse. For example, we did not examine job stressors (which have been linked to hypertension (13
) because of the large representation of retirees (34%) in this sample. Additionally, the stressors we did include are subject to measurement error. Defensiveness or denial may cause an under-reporting of discriminatory acts whereas anger and hostility may lead to over-reporting. (39
) Our measure of neighborhood stressors was based on prior work, however we did not have all items that comprised previously validated scales of neighborhood disorder. (20
) Despite this exclusion, we found that our measure had good internal consistency and test-retest reliability. Limitations of our measures of stress (in both type and measurement) may have contributed to our inability to detect an association between stressors and hypertension in adjusted models.
As an additional concern, neighborhood chronic stressors may cluster with other features of neighborhood infrastructure. This creates difficulty in teasing out whether it is the stressors or the physical features of neighborhoods associated with them, which contribute to hypertension. In our data, the neighborhood stressors scale was moderately correlated with neighborhood measures of walkability (r=−0.45) and availability of healthy foods (r=−0.33). Additional adjustment for these factors did not further reduce race/ethnic differences although this may be because the neighborhood stressor scale was already capturing these other neighborhood attributes.
Other limitations include limited overlap in the neighborhood stressors by race/ethnicity. For example, 79.8% of Hispanics lived in neighborhoods with the highest tertile of neighborhood stressors as compared to only 12.0% of whites. Regression results are therefore based on extrapolations to areas of sparse data, but we believe these extrapolations are reasonable. Another limitation is the inability to fully capture the accumulation of chronic stressors (at the neighborhood level) to impact a chronic condition like HTN that develops over the lifecourse. In our sample, 44.1% of respondents have resided in the current neighborhood for 20 or more years. We did not find any statistically significant interactions between time lived in neighborhood and neighborhood stressors in relation to hypertension prevalence. The absence of effect modification by time lived in neighborhood could have resulted from individuals being exposed to similar conditions in previous neighborhoods. However, we had limited statistical power to detect significant interactions.
In summary, in this ethnically diverse sample we found that cross-sectional associations between race/ethnicity and hypertension were reduced after accounting for chronic stressors at the neighborhood level. Although these results need to be confirmed in longitudinal and lifecourse designs, they suggest that multilevel sources of stress may contribute to race/ethnic disparities in hypertension. Future work also needs to examine the behavioral and biologic mechanisms though which stressors may be related to hypertension. Our findings suggest that efforts to reduce race/ethnic disparities in high blood pressure may benefit from consideration of possible stress inducing features of neighborhoods.