Fatigue, Fatigability, and Mortality Risk Among Older Adults

Fatigue has received increased attention in aging research. Despite the importance of fatigue as an independent risk factor for disability and mortality, the current understanding of how fatigue is linked to these outcomes is very limited. Because of the subjective nature of the fatigue measure, it is important to examine the role of fatigability (the feeling of tiredness as a function of physical activity) in the relationship between fatigue symptom and mortality risk. We used the longitudinal data from the Health and Retirement Study (HRS), a nationally representative sample of community-dwelling U.S. older adults aged 51 and above to study the relationship between fatigue, fatigability, and mortality. The sample of 10,799 individuals who completed the 2004 telephone interview was followed for four years. We used multivariate Cox proportional Hazards model to estimate the effect of fatigue on mortality for physically active and inactive individuals. Fatigue was more common in women (33.3%) than in men (28.6%). Individuals who reported having fatigue symptom were 17% (OR=1.17, 95% CI: 1.04, 1.31) more likely to die. However, the adverse effect of fatigue on mortality was only present among physically active individuals (OR=1.36, 95% CI: 1.06,1.74). These findings suggest that fatigability is an important concept in the study of fatigue. Fatigue symptoms may be an important predictor of adverse outcomes among middle-aged and older adults who are physically active.