摘要：Objectives. We examined the social patterning of cumulative dysregulation of multiple systems, or allostatic load, among African Americans adults. Methods. We examined the cross-sectional associations of socioeconomic status (SES) with summary indices of allostatic load and neuroendocrine, metabolic, autonomic, and immune function components in 4048 Jackson Heart Study participants. Results. Lower education and income were associated with higher allostatic load scores in African American adults. Patterns were most consistent for the metabolic and immune dimensions, less consistent for the autonomic dimension, and absent for the neuroendocrine dimension among African American women. Associations of SES with the global allostatic load score and the metabolic and immune domains persisted after adjustment for behavioral factors and were stronger for income than for education. There was some evidence that the neuroendocrine dimension was inversely associated with SES after behavioral adjustment in men, but the immune and autonomic components did not show clear dose–response trends, and we observed no associations for the metabolic component. Conclusions. Findings support our hypothesis that allostatic load is socially patterned in African American women, but this pattern is less consistent in African American men. The adaptation of biological systems in response to stress and the maintenance of allostasis is a critical component in maintaining internal viability and functioning. 1 Exposure to social and environmental stressors can result in physiologic dysregulation of multiple systems in the human body, often referred to as allostatic load. 2,3 Allostatic load has been operationalized in epidemiological studies using combinations of biomarkers chosen to reflect the various physiological systems that may be affected by frequent and repeated exposure to stress. 4,5 Measures of allostatic load have been linked to numerous disease-related processes, 6 including cardiovascular 4,7 and all-cause 8 mortality. Because chronic stressors are often inversely associated with socioeconomic status (SES), 9 it has been hypothesized that allostatic load may at least partly mediate the socioeconomic differences in cardiovascular disease and other health outcomes. 10,11 To build evidence for this argument, numerous epidemiological studies have examined the socioeconomic patterning of allostatic load. In most studies, higher SES was associated with lower allostatic load, 4,12–18 although at least 2 studies observed that this association was attenuated after adjustment for behavioral 17 and psychosocial factors. 18 The majority of US studies of SES and allostatic load, however, have focused predominantly on White samples. 4,12–14 Relatively few studies have examined these associations in African American population samples and the extent to which these associations vary by gender or type of socioeconomic indicator used. 12,13 There are several reasons investigation of the SES patterning of allostatic load in African Americans is of interest. African Americans have been shown to have higher allostatic load scores 19–21 and are more frequently exposed to chronic social and economic stressors 9,22,23 than are Whites. This suggests that allostatic load could play a greater role in the SES patterning of cardiovascular and other health outcomes in African Americans than in Whites. If allostatic load truly reflects the dysregulation of biological systems because of repeated exposure to chronic stressors, a stronger SES–allostatic load gradient in African Americans would lend support for a more prominent role of psychosocial factors and stressors in the SES gradient in African American health. In investigating SES gradients in allostatic load in African Americans, variations by gender and SES measure used may be of special importance. Numerous studies have suggested that the SES gradient in cardiovascular risk factors (several of which are related to allostatic load measures) differs for men and women, 24–29 although the underlying reasons for this remain to be determined. Although 2 studies have examined gender differences in the social patterning of allostatic load in African Americans, 12,13 the results have been mixed and this patterning has not been extensively investigated in large African American samples. There is some evidence that the validity of various SES indicators may differ by race. For example, African Americans, compared with Whites, have been shown to have lower economic returns to education. 30 Therefore, the socioeconomic patterning of allostatic load in African Americans could differ depending on the SES indicator used. Most prior research on the socioeconomic patterning of allostatic load has focused on educational attainment, 6,12–16,18 with fewer studies considering income 12–15 and occupation. 17 An important challenge in studying SES differences in allostatic load is identifying whether any observed associations reflect cumulative exposures to chronic stressors with consequences for multiple biological systems (as posited by the allostatic load theory) or whether the associations simply reflect socioeconomic patterning of behaviors. This is especially important given that many of the functional components of allostatic load (e.g., blood pressure and metabolic factors) are strongly influenced by behavioral factors (e.g., smoking and dietary intake). An added complexity is that behaviors may also partly mediate the effects of chronic stress on allostatic load. For these reasons, it is important for epidemiological studies to investigate associations of SES with allostatic load before and after controlling for behavioral factors. Using data from the Jackson Heart Study (JHS), we examined the extent to which education and income were cross-sectionally associated with a summary measure of allostatic load and allostatic load subcomponents in a large community-dwelling African American sample. We hypothesized that allostatic load would be inversely patterned by SES. According to prior evidence of stronger SES patterning of cardiovascular risk in women than in men 27,28 and evidence of limited return to education in African Americans, 30 we hypothesized that the SES patterning would be stronger in women than in men and stronger for income than for education. We also examined to what extent the associations between allostatic load and SES persisted after adjustment for behavioral factors: cigarette smoking, physical activity, dietary intake, alcohol consumption, and sleep duration. The large and heterogeneous JHS population makes the JHS ideally suited for our investigation in terms of SES and the availability of detailed information on allostatic load biomarkers and behavioral factors.
