Abstract Body: Background: Perceived physical fatigability (i.e., fatigue experienced in response to activities of standardized intensity and duration) is a sensitive, person-reported outcome measure and strong prognostic indicator of age-related functional decline and cardiometabolic health. Modifiable lifestyle behaviors such as physical activity and sleep may influence fatigability. Evidence linking these lifestyle behaviors to fatigability in diverse older populations is limited. We examined accelerometer-measured daily activity and sleep by perceived physical fatigability severity among 205 African Caribbean men from the population-based Tobago Health Study.

Methods: Men wore an ActiGraph CentrePoint Insight Watch for 7-days on their non-dominant wrist to measure activity and sleep. Daily step count was derived using the modified Verisense algorithm from the GGIR R package. Sleep measures were estimated with the HDCZA sleep detection algorithm during the nocturnal sleep period. Perceived physical fatigability was assessed using the Pittsburgh Fatigability Scale, modified for the Caribbean (PFS; range 0-50; higher PFS score=greater fatigability). PFS Physical scores were classified into 6 established severity strata.

Results: Men were mean±SD 68.0±4.3 years old, overweight (BMI=27.7±5.1 kg/m²), and had 1.03±0.23 m/s 4-meter gait speed. Mean PFS score was 20.0±8.1; prevalence of more severe fatigability (PFS≥15) was 71%. Daily step counts were lower by 51% across fatigability severity strata ranging from 11,586±4,376 (least severe) to 5,640±3,461 (most severe, PFS≥25) steps/d, p_trend<0.001 (Table 1). Mean sleep duration (5.3±1.1 hours/d) and wake after sleep onset (1.4±0.6 hours/d) did not differ across fatigability severity strata, both p>0.15. Sleep regularity (i.e., day-to-day consistency of sleep-wake timing) differed across severity strata, p_trend=0.02.

Conclusion: Our novel data reveal an approximately two-fold higher burden of perceived physical fatigability in our Caribbean population, substantially greater than reported in age-comparable Caucasian men, despite high activity levels. Both lower daily activity and less regular sleep patterns were associated with fatigability severity, suggesting fatigability, a predictor of functional decline, may represent a multidimensional phenotype of lifestyle behaviors. Future work will extend to women and explore additional modifiable factors associated with perceived physical fatigability in African Caribbean populations.