Assessing Fatigability in the Lab and in Daily Life in Older Adults With Osteoarthritis Using Perceived, Performance, and Ecological Measures.

Abstract

Fatigue in older adults is associated with functional decline and reduced participation in daily life; however, it is not well characterized. Examining fatigue within activity performance, or "fatigability," is a recommended approach to begin to understand fatigue and its underlying mechanisms. This study examined the construct validity of lab-based measures of fatigability and compared these measures with fatigability in daily life (termed ecological fatigability). Participants with osteoarthritis and fatigue (n = 163) underwent laboratory assessments, completed questionnaires, and wore accelerometers for 7 days while tracking symptoms and behaviors. Lab-based fatigability measures were quantified using the 6-minute walk test. Perceived fatigability was assessed by asking participants before and after the test to report: (i) fatigue severity and (ii) perceived exertion. Performance fatigability was calculated using change in walking speed divided by total distance walked. Ecological fatigability was calculated from the 7-day assessment in which fatigue severity was reported five times a day and physical activity was continuously measured. Additional ecological measures (eg, self-pacing) were examined. Lab-based perceived and performance fatigability measures were highly inter-correlated, moderately correlated with gait speed and metabolic measures, and weakly correlated with physical activity. Although ecological fatigability was weakly correlated with lab-based measures, participants with high fatigability on lab-based measures demonstrated more self-pacing behaviors than participants with low fatigability. Lab-based fatigability measures are related to physical capacity measured both in the lab and daily life. Lab-based fatigability measures provide important information regarding daily life fatigability useful for future intervention development.