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

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.

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.

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.

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.