Life-space Mobility in Older Men: The Role of Perceived Physical and Mental Fatigability

Background Physical performance and fatigue can limit mobility within the larger environment (life-space mobility). It is unknown whether perceived fatigability, self-reported fatigue anchored to activity intensity and duration, is independently associated with life-space. Methods We assessed this cross-sectionally in Visit 4 (2014-2016) of the Osteoporotic Fractures in Men Study (MrOS; N = 1 672, Age: Mean = 84.2 +/- 4.0 years). The Pittsburgh Fatigability Scale (PFS, range: 0-50; higher = greater fatigability) measured physical (Mean = 16.1 +/- 9.4) and mental fatigability (Mean = 7.5 +/- 7.9). Life Space Assessment scores incorporated level, frequency, and assistance used for life-space mobility (range: 0-120, higher = greater life-space mobility; life-space constriction: inability to leave neighborhood without assistance). Separate multiple linear and logistic regressions for physical and mental fatigability were sequentially adjusted for demographic, health/lifestyle, and performance measures. Results The mean life-space mobility score was 84.6 +/- 21.8, and 18% (n = 296) of men had life-space constriction. Higher physical and mental fatigability were both associated with lower life-space mobility in models adjusted for health and lifestyle factors (Physical PFS: B = -2.37, 95% confidence interval [CI]: [-3.39, -1.35]; Mental PFS: B = -1.79, 95% CI: [-2.73, -0.84]). Men with higher fatigability also had increased risk of life-space constriction (Physical PFS: OR = 1.59, 95% CI: [1.32, 1.92]; Mental PFS: OR = 1.25, 95% CI: [1.08, 1.46]). Associations were larger in magnitude for physical versus mental fatigability. Adjusting for physical performance measures more strongly attenuated associations for physical compared to mental fatigability. Conclusions Fatigability is linked with real-world mobility in older men, independent of their physical health. This association may be driven by separate physical and cognitive mechanisms worth examining further in longitudinal studies.