"Heat Shock Proteins, Cognition, and Pain in Older Adults" by Cayla E. Clark, Kelsi R. Lambright et al.
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Abstract

Heat shock proteins (HSP) are cellular chaperones that regulate protein metabolism. Aging elicits reductions in HSP expression; however, elevated levels of HSP70 may be neuroprotective against the deleterious effects of aging. PURPOSE: To observe the concentration of HSP70 expression, cognitive performance, and self-perceived pain following one hour of aerobic exercise or whole-body passive heating in older adults. METHODS: Twenty-four older adults (68.1±4.6 yrs, 27.1±4.0 kg/m2, 12 female) randomly completed either one hour of moderate-intensity walking on a treadmill (TM), one hour of seated passive heating (HEAT) in a controlled environmental heat chamber (34 to 40ºC, 30% humidity), or one-hour of seated control (CON) in a thermoneutral environment (21 to 23ºC). Protein expression was measured via blood samples with an enzyme-linked immunosorbent assay (ELISA) kit for concentrations of HSP70. Blood samples were collected before, immediately after, and 24 hours following each intervention. Cognitive performance, including reaction time, cognitive flexibility, and response inhibition, was assessed using computerized software (Automated Neuropsychological Assessment Metrics, Vista LifeSciences Inc., Parker, CO). Pain was assessed via a self-reported pain scale questionnaire (McGill Pain Questionnaire). Both cognitive performance and pain were assessed before and immediately after each intervention. Multiple analysis-of-variance (ANOVAs) repeated for time were conducted with a Tukey post-hoc test employed to reveal any differences between groups and time. A significance level of 0.05 was used. RESULTS: There were no statistical differences for HSP70 concentration between groups or time (p>0.05). Pain was perceived higher in HEAT and TM compared to control (29.1±9.1 and 24.9±20.8, respectively vs. 9.2±9.8; p=0.0258). Reaction time improved following each intervention (ηp2=0.234, p=0.019). Post hoc analyses revealed a significant difference between pre- and post-intervention within CON (2861.9±1051.4 vs. 2620.3±858.2 msec, respectively; p=0.0397) and TM (2209.1±337.2 vs. 1965.6±280.2 msec, respectively; p=0.0279), but not following HEAT (2432.5±443.2 vs. 2305.9±512.1 msec, respectively; p=0.2319). Cognitive flexibility improved following each intervention across conditions (ηp2=0.218, p=0.026), but no differences were observed between conditions (p>0.05). Response inhibition also improved following each intervention across conditions (ηp2=0.214, p=0.025). Post hoc analyses revealed a significant difference between pre- and post-intervention only within TM (31.1±6.5 vs 34.0±6.9, respectively; p=0.0471). CONCLUSION: One bout of moderate-intensity aerobic exercise or whole-body passive heating may not illicit changes in HSP70 expression or impair cognitive performance in older adults. There could be an anticipatory psychological affect resulting in different perceptions of pain for passive heating and exercise. Future studies are encouraged to correlate core body temperature with changes in HSP expression.

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