title: Relationship between fatigue and subsequent physical activity among older adults with symptomatic osteoarthritis.
abstract: OBJECTIVE
  Although it has been well established that fatigue is common among older adults with osteoarthritis (OA), relatively little is known about how fatigue in daily life affects physical activity. The purposes of this study were to examine the relationship between momentary fatigue and subsequent physical activity among people with OA who reported clinically relevant levels of fatigue and to examine moderators of this relationship.
  
  
  METHODS
  People with knee or hip OA and clinically relevant fatigue participated in physical performance assessments, completed questionnaires, and underwent a home monitoring period in which fatigue severity was measured 5 times/day over 5 days (n = 172). Physical activity was concurrently measured via a wrist-worn accelerometer. Multilevel modeling was used to examine the relationship of momentary fatigue and subsequent activity controlling for other factors (e.g., age, body mass index, pain, and depression).
  
  
  RESULTS
  Fatigue was the strongest predictor of reduced subsequent activity. Only functional mobility (Timed Up and Go) moderated the relationship between fatigue and activity. The relationship between fatigue and activity was strongest for people with high functional mobility.
  
  
  CONCLUSIONS
  Momentary fatigue is a robust and important variable associated with decreased physical activity. Further, the moderating effect of functional mobility suggests this factor should be considered when intervening on fatigue. While people with better functional mobility may benefit from an activity-based treatment approach (such as learning activity pacing techniques to reduce the impact of fatigue on activity), those with worse functional mobility may benefit from treatment focusing on underlying impairments.
authors.affiliation: University of Michigan and VA Ann Arbor Health Care System, Ann Arbor.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Murphy
authors.forename: Neil B
authors.initials: NB
authors.lastname: Alexander
authors.forename: Melissa
authors.initials: M
authors.lastname: Levoska
authors.forename: Dylan M
authors.initials: DM
authors.lastname: Smith
mesh_terms: D056044:Actigraphy; D000203:Activities of Daily Living; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005221:Fatigue / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D015999:Multivariate Analysis; D015207:Osteoarthritis, Hip / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D011237:Predictive Value of Tests; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013997:Time Factors