Muscle Endurance and Self-Perceived Fatigue Predict Decline in Gait Speed and Activities of Daily Living After 1-Year Follow-Up: Results From the BUTTERFLY Study

Abstract Background Fatigue might influence the losses in activities of daily living (ADL). When fatigue parameters are present before the experience of losses in ADL and gait speed, they can be used as early warning signals. This study aimed to explore the predictive value of muscle endurance and fatigue on changes in ADL and gait speed in community-dwelling older adults aged 80 and older. Methods Three hundred twenty four community-dwelling older adults aged 80 and older of the BUTTERFLY study were assessed after 1 year for muscle endurance, self-perceived fatigue, ADL, and gait speed. Exploratory factor analysis (EFA) was performed to explore, whether there is an underlying arrangement of the fatigue parameters. Mediating logistic regression analyses were used to investigate whether muscle endurance mediated by self-perceived fatigue predicts the decline in gait speed and ADL after 1-year follow-up. Results EFA indicated a 2-factor model (muscle endurance factor and self-perceived fatigue factor) and had a moderate fit (X2: 374.81, df: 2, comparative fit index; 0.710, Tucker–Lewis index (TLI): 0.961, root mean square error of approximation [90%]: 0.048 [0.00–0.90]). Muscle endurance mediated by self-perceived fatigue had an indirect effect on the prediction of decline in Basal-ADL (−0.27), Instrumental-ADL (−0.25), and gait speed (−0.28) after 1-year follow-up. Conclusion This study showed that low muscle endurance combined with high self-perceived fatigue can predict changes in ADL after 1-year follow-up. These parameters might be very suitable for use in evaluating intrinsic capacity and can help to reduce the limitations in clinical usage of the vitality domain in the framework of intrinsic capacity.