Graduation Year

2012

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

School of Aging Studies

Major Professor

Brent J. Small

Keywords

Cognition, Cytokines, Elderly, HPA Axis, Immune System

Abstract

ABSTRACT

With aging, changes in the immune system, makes cognitive performance, and the prevalence of stressors can lead to poorer overall functioning. Within the immune system, a balance should exist between cytokines regulating Th1 and Th2 immune responses; however, age-related declines in the endocrine and immune systems can disrupt this equilibrium. Several studies report higher levels of Th1 associated cytokines in inflammatory conditions of the brain, whereas fewer studies remark on Th2 associated cytokines and cognitive functioning. Declining cognitive abilities are a common concern that accompanies advancing age and some research has suggested the prevalence and impact of stressors lead to poorer performance.

Participants included 92 older adults (M = 74.05 years) who completed tests of cognitive performance and stress measures, and 41 persons who had valid data on Th1 and Th2 cytokines. The results indicated that increasing age is significantly associated with several cognitive domains including executive functioning, speed of processing, and episodic memory. As hypothesized, moderation analysis revealed the relationship between Th1 and Th2 cytokinic profiles, as denoted by the IFN-γ/IL-4 ratio, is a significant moderator between stress and cognitive performance. Specifically, immune profiles skewed towards Th1 predict a significant amount of variation between high stress scores and low cognitive performance, whereas this was not found for immune profiles skewed towards Th2. Overall, the current study suggests that a pro-inflammatory state permits stress to exert a negative influence on cognitive performance.

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