films depicting racist incidents, imagery related to racism) than to nonracist stimuli (Armstead et al., 1989; Guyll et al., 2001). Blacks also show greater blood pressure reactivity than whites to discrimination and unfair treatment (Guyll et al., 2001). However, the contribution of such responses to black-white differences in the prevalence of hypertension has not been determined.

ALLOSTATIC LOAD

Allostatic load is another concept developed to explain how psychosocial factors might affect biological systems in potentially pathogenic ways (McEwen and Stellar, 1993). It is defined as the overtaxing of several physiological systems (“wear and tear”) in response to stress or other psychosocial or behavioral factors, so that dysregulation and possibly disease may develop. The concept of allostatic load incorporates the notion of physiological reactivity, but it also includes other physiological changes that might be pathogenic. Those changes include having a chronically high level of resting physiological activity (e.g., high levels of stress hormones or high blood pressure); an exaggerated physiological response to psychosocial challenges; the relative inability of the physiological system to recover after acute stress; and, over time, an inadequate physiological response to stress (low reactivity) due to fatigue or dysfunction, which triggers potentially harmful compensatory responses from other systems (McEwen, 1998; Myers and Hwang, 2004). In essence, allostatic load represents a cumulative, multisystems perspective on physiological risk.

Recent research on the Macarthur Successful Aging Cohort indicates that high levels of allostatic load predict morbidity and mortality among older adults. For instance, Seeman et al. (1997) have discovered that higher allostatic load scores are prospectively associated with increased incidence of cardiovascular disease and increased risk for decline in cognitive and physical functioning in older adults. Allostatic load scores have been found to be higher among persons with lower educational attainment and higher levels of hostility than average, suggesting a potential role for allostatic load in the greater disease risk in these populations (Kubzansky et al., 1999). To date, racial and ethnic group differences in allostatic load and the role of such differences in health differences have not been explored.

PSYCHONEUROIMMUNOLOGY

Psychoneuroimmunology is defined as the examination of the interactions among psychological, behavioral, and social factors with immunological and neuroendocrine outcomes. It is now well established that psychological factors, especially chronic stress, can lead to impairments in immune system



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