title: Pain, Fatigue, and Physical Activity in Osteoarthritis: The Moderating Effects of Pain- and Fatigue-Related Activity Interference.
abstract: To examine how self-reported pain- and fatigue-related activity interference relates to symptoms and physical activity (PA) in daily life among people with knee or hip osteoarthritis.
  
  
  
  Cross-sectional study with a 7-day repeated-measures assessment period.
  
  
  
  General community.
  
  
  
  Participants (N=154; mean age, 65y; 60% women [n=92]) with knee or hip osteoarthritis and pain lasting ≥3 months.
  
  
  
  Not applicable.
  
  
  
  Pain- or fatigue-related activity interference items on the Brief Pain Inventory or Brief Fatigue Inventory, respectively, from baseline survey, momentary pain and fatigue severity (measured 5times/d for 7d), and PA measured with a wrist-worn accelerometer over 7 days. We hypothesized that perception of pain- and fatigue-related activity interference would moderate the association between symptoms (pain or fatigue) and PA. People with higher pain- or fatigue-related activity interference were thought to have stronger negative associations between momentary ratings of pain and fatigue and PA than did those with lower activity interference.
  
  
  
  Pain-related activity interference moderated the association between momentary pain and PA, but only in the first part of the day. Contrary to expectation, during early to midday (from wake-up time through 3 pm), low pain-related interference was associated with stronger positive associations between pain and PA but high pain-related interference was associated with a small negative association between pain and PA. Fatigue-related activity interference did not moderate the relation between fatigue and activity over the course of a day.
  
  
  
  Depending on a person's reported level of pain-related activity interference, associations between pain and PA were different earlier in the day. Only those with high pain-related activity interference had lower levels of PA as pain increased and only in the morning. High pain-related activity interference may be important to address, particularly to maintain PA early in the day despite pain.
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI; VA Ann Arbor Health Care System (Geriatric Research, Education, and Clinical Center), Ann Arbor, MI. Electronic address: sumurphy@umich.edu.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Murphy
authors.affiliation: Mrs. T.H. Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, CA.
authors.forename: Stacey
authors.initials: S
authors.lastname: Schepens Niemiec
authors.affiliation: Department of Anesthesiology, University of Michigan, Ann Arbor, MI.
authors.forename: Angela K
authors.initials: AK
authors.lastname: Lyden
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Kratz
mesh_terms: D061725:Accelerometry; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D015444:Exercise; D005221:Fatigue / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000150:complications*; D020370:Osteoarthritis, Knee / Q000150:complications*; D010146:Pain / Q000209:etiology*; D010147:Pain Measurement; D058748:Pain Perception; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: Accelerometry; Chronic pain; Fatigue; Osteoarthritis; Rehabilitation