title: Fatigue and fatigability in older adults.
abstract: Fatigue is believed to be a common complaint among older adults; however, multiple studies of self-reported fatigue across the lifespan have found this may not be the case. To explain this paradox, this article considers "fatigability"-a phenotype characterized by the relationship between an individual's perceived fatigue and the activity level with which the fatigue is associated. Fatigability may be measured by combining self-report measures of fatigue with performance of physical or cognitive activities, provided that the work of the activity is known or can be standardized. Doing so prevents self-pacing and allows meaningful comparisons across subjects and between studies. Increased fatigability with aging may arise from a variety of factors including age-related changes in energy production or utilization, and inflammatory mechanisms. A few published intervention studies have targeted fatigue in older adults, though none have examined fatigability specifically. Because fatigue may represent a physiologic warning system, future clinical studies may benefit from a focus on fatigability, where both symptoms and function are considered.
authors.affiliation: Division of Geriatrics and Clinical Gerontology, National Institute on Aging, 7201 Wisconsin Avenue, Bethesda, MD 20892-9205, USA. eldadahb@nia.nih.gov
authors.forename: Basil A
authors.initials: BA
authors.lastname: Eldadah
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D004734:Energy Metabolism; D005221:Fatigue / Q000145:classification / Q000453:epidemiology* / Q000503:physiopathology*; D006305:Health Status Indicators; D006801:Humans; D009043:Motor Activity / Q000502:physiology; D010101:Oxygen Consumption; D015995:Prevalence