Physical activity, sleep quality, and self-reported fatigue across the adult lifespan.

Deteriorating sleep quality and increased fatigue are common complaints of old age, and poor sleep is associated with decreased quality of life and increased mortality rates. To date, little attention has been given to the potential effects of physical activity on sleep quality and fatigue in aging. The purpose of this study was to examine the relationships between activity, sleep and fatigue across the adult lifespan. Sixty community-dwelling adults were studied; 22 younger (21-29 years), 16 middle-aged (36-64 years), and 22 older (65-81 years). Physical activity was measured by accelerometer. Sleep quality was assessed using the Pittsburg Sleep Quality Index. Self-reported fatigue was evaluated with the Patient-Reported Outcomes Measurement Information System (PROMIS). Regression analysis revealed a positive relationship between activity and sleep quality in the older (r(2)=0.18, p=0.05), but not the younger (r(2) = 0.041, p = 0.35) or middle-aged (r(2) = 0.001, p = 0.93) groups. This association was mainly established by the relationship between moderate-vigorous activity and sleep quality (r(2)=0.37, p=0.003) in older adults. No association was observed between physical activity and self-reported fatigue in any of the groups (r(2) ≤ 0.14, p ≥ 0.15). However, an inverse relationship was found between sleep quality and fatigue in the older (r(2) = 0.29, p = 0.05), but not the younger or middle-aged (r(2) ≤ 0.13, p ≥ 0.10) groups. These results support the hypothesis that physical activity may be associated with sleep quality in older adults, and suggest that improved sleep may mitigate self-reported fatigue in older adults in a manner that is independent of activity.