Relationship between objectively assessed physical activity and fatigue in patients with rheumatoid arthritis: inverse correlation of activity and fatigue.

Abstract

Fatigue is generally associated with low physical activity in patients with various chronic medical conditions. However, such an association has not been reported among patients with rheumatoid arthritis (RA). The objectives of this study were to investigate whether daily activity level is associated with fatigue in patients with RA, and whether pain, disability, coping, and/or cognition are associated with the level of daily activity. Patients with RA who visited our outpatient clinic were recruited consecutively. Fatigue severity was measured using the Checklist Individual Strength (CIS20). Physical activity was measured for 14 consecutive days using an ankle-worn actometer. The daily activity level of each patient was calculated, and each patient was classified as having a low or high activity level with respect to the group average. Data were analyzed by linear regression. A total of 167 patients were included in the analysis; 25% had a low activity level and 75% had a high activity level. A regression analysis revealed that higher activity levels were associated with reduced fatigue (P = 0.008). The mean ± SD CIS fatigue score was 30.9 ± 12.3 among the patients with a high activity level and 35.7 ± 12.8 among the patients with a low activity level (P = 0.03). Pain, disability, coping, and cognition were not associated significantly with daily activity level. Among patients with RA, a higher level of daily physical activity was associated with reduced levels of fatigue. This relationship was not explained by differences in sex, age, disease duration, pain, disability, or other fatigue-related factors.