Examining Biobehavioral Mechanisms of Physical Disability Disparities in US Midlife and Older Adults.

TitleExamining Biobehavioral Mechanisms of Physical Disability Disparities in US Midlife and Older Adults.
Publication TypeThesis
Year of Publication2016
AuthorsThierry, AD
Academic DepartmentBiobehavioral Health
Date Published06/2016
UniversityPennsylvania State University
CityHappy Valley, PA
Thesis TypeDissertation
KeywordsChronic stress, Disabilities, Telomeres

US population projections estimate that the number of adults over the age of 65 will double by 2050. In addition, chronic conditions and associated physical disability are increasing, particularly among racial/ethnic minorities. Although the role of psychosocial factors has been acknowledged in promoting development of physical disability, there is a dearth of research examining if chronic stress contributes to disparities. Therefore, three studies examined chronic stress-associated biobehavioral mechanisms that may explain higher rates of disability in black and Mexican American midlife and older adults compared to whites. Data used in these studies were drawn from the Health and Retirement Study (HRS), a longitudinal survey of a nationally representative sample of US adults over the age of 50. Using data from the 2006 HRS wave of data collection, the first study examined differences in prevalence of eight chronic stressors by race/ethnicity and gender. Then, the relationship between number of chronic stressors and number of physical disabilities, measured as difficulty with functional limitations, activities of daily living (ADLs), and instrumental activities of daily living (IADLs), was tested. Differences in the chronic stress-disability relationship were assessed by race/ethnicity and gender. Because unhealthy behaviors may be used as mechanisms to cope with stress, a second study using 2006 HRS data tested if unhealthy behavior-related risk factors—including currently smoking, heavy drinking, and being obese—moderated the relationship between chronic stress and physical disability. The contribution of unhealthy behaviors to racial/ethnic and gender disparities in physical disability outcomes, net of age, SES, and health status, was also assessed. Lastly, a third study assessed if telomere length, a biomarker of cellular age that may shorten from exposure to stress, may be implicated in physical disability development. This study tested the relationship between telomere length measured in 2008 and change in number of physical disabilities across a 6-year study period. Analytic results demonstrated that, on average, blacks and Mexican Americans reported more chronic stressors than whites. Overall, chronic stress was positively associated with physical disability. The gap in number of ADLs and IADLs between blacks and whites widened with increasing numbers of chronic stressors, while the number of these disabilities in Mexican Americans was less dependent upon chronic stress. Unhealthy behavioral risk factors moderated the chronic stress-disability relationship for ADLs and IADLs, such that increasing disability and number of chronic stressors were more pronounced in individuals with one or more unhealthy behavioral risks. Lastly, individuals with longer telomeres accumulated fewer disabilities over time. However, this relationship was found only in adults over 65, and did not depend on race/ethnicity or gender. Results from these three studies suggest that chronic stress may differentially increase risk for physical disability in blacks, and unhealthy behavioral risks may exacerbate disability development. Finally, telomere length may be involved in the disablement process such that shorter telomeres may promote the development of disability over time.

Citation Key8984