Less is More: The Relationship between the Perceived Stress Scale and Cognitive Decline
Jiang, Julie M.
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The number of adults over the age of 65 years old is projected to grow from 524 million worldwide in 2010 to nearly 1.5 billion in 2050. Cognitive decline is highly associated with age. Alzheimer's dementia, the leading cause of dementia, is the 6th leading cause of death in the United States. It is important to identify potentially remediable risk factors to delay or prevent cognitive decline. Stress has been identified as a risk factor for cognitive decline. This thesis explored the relationship between subjective stress as measured by the Perceived Stress Scale (PSS) and cognitive decline. The study was conducted as part of the Einstein Aging Study (EAS), a prospective, longitudinal study of community-residing adults over the age of 70. We validated the PSS for use in the older adult population. As in other studies, we found that the PSS is made up of two factors. One factor is composed of positively worded questions (PSS-PW) and the other factor is made up of negatively worded questions (PSS-NW). Next, we found that the PSS-PW, but not the PSS-NW, predicted the incidence of dementia in older adults with amnestic mild cognitive impairment (aMCI). Very few studies use the subscales of the PSS separately, but instead use the PSS as one score. This prompted an investigation into the validity of the two PSS subscales. Both the PSS-PW and PSS-NW showed adequate validity and reliability as measured by Cronbach's alpha and intraclass correlation. Both the PSS-PW and PSS-NW were associated with depression, neuroticism, and negative affect. The PSS-NW was uniquely associated with anxiety while the PSS-PW was uniquely associated with positive affect. The PSS-PW, but not the PSS-NW, predicted the incidence of aMCI. Finally, we examined the cross sectional relationship of the PSS-PW and PSS-NW with cognitive domain function in older adults with normal cognition. The PSS-PW was associated with the global domain, episodic memory domain, and the frontal-executive domain. The PSS-NW was not associated with any cognitive domain. This work shows that perceived stress, as measured by the PSS-PW score, is associated with cognitive decline in older adults. It demonstrates that the two factors of the PSS have different properties as predictors of cognitive events, specifically incident aMCI and incident dementia. It may not be appropriate to simply combine the two factors into a summary score. Future studies should clarify the mechanisms which link subjective stress to cognition. In addition, interventions which influence PSS-PW might merit evaluation in the prevention of cognitive decline in older adults.