Associations of Actigraphic Sleep Parameters with Fatigability in Older Adults

Background: Poor sleep may increase the likelihood of fatigue, and both are common in later life. However, prior studies of the sleep-fatigue relationship used subjective measures or were conducted in clinical populations; thus, the nature of this association in healthier community-dwelling older adults remains unclear. We studied the association of actigraphic sleep parameters with perceived fatigability - fatigue in response to a standardized task - and with conventional fatigue symptoms of low energy or tiredness. Methods: We studied 382 cognitively normal participants in the Baltimore Longitudinal Study of Aging (aged 73.1 ± 10.3 years, 53.1% women) who completed 6.7 ± 0.9 days of wrist actigraphy and a perceived fatigability assessment, including rating of perceived exertion (RPE) after a 5-minute treadmill walk or the Pittsburgh Fatigability Scale (PFS). Participants also reported non-standardized symptoms of fatigue. Results: After adjustment for age, sex, race, height, weight, comorbidity index, and depressive symptoms, shorter total sleep time (TST; <6.3 hours vs intermediate TST =6.3 to 7.2 hours) was associated with high RPE fatigability (odds ratio [OR] = 2.56, 95% confidence interval [CI] = 1.29, 5.06, p =. 007), high PFS physical (OR = 1.88, 95% CI = 1.04, 3.38, p =. 035), and high mental fatigability (OR = 2.15, 95% CI = 1.02, 4.50, p =. 044), whereas longer TST was also associated with high mental fatigability (OR = 2.19, 95% CI = 1.02, 4.71, p =. 043). Additionally, longer wake bout length was associated with high RPE fatigability (OR = 1.53, 95% CI = 1.14, 2.07, p =. 005), and greater wake after sleep onset was associated with high mental fatigability (OR = 1.14, 95% CI = 1.01, 1.28, p =. 036). Conclusion: Among well-functioning older adults, abnormal sleep duration and sleep fragmentation are associated with greater perceived fatigability.