Background/Purpose: Fatigue is recognized as a major problem for individuals with rheumatoid arthritis (RA), yet the causes of fatigue are not well defined. Obesity appears to be common in RA, and studies outside RA have linked obesity with fatigue. This analysis examined the association of obesity with fatigue in RA.
Methods: Subjects are participants in an on-going study of RA fatigue (current n=136). Home visits are made to individuals with documented RA to assess a number of factors, including the following variables used to estimate body composition: height, weight, waist circumference, and bioelectrical impedance analysis (BIA). Height and weight were used to calculate body mass index (BMI). Obesity was defined by standard definitions of BMI (≥30 kg/m2) and waist circumference (women: ≥88cm; men: ≥102cm). Revised definitions of obesity from BMI (≥26 kg/m2) and waist circumference (women: ≥83 cm; men: ≥96 cm)* were also examined. Total percent body fat was calculated from BIA. Fatigue was measured with the Fatigue Severity Index, and used the rating of average fatigue severity over the past week (range 0-10, no fatigue to severe fatigue). Subjects also completed questionnaires to measure RA disease activity (RA Disease Activity Index [RADAI]), sleep quality (Pittsburgh Sleep Quality Index [PSQI]), depression (PHQ), and functioning (HAQ). Multiple linear regression analyses were used to identify the association of each measure of obesity with fatigue severity. Covariates included RADAI, PHQ, HAQ, sleep quality, age, sex, and RA duration.
Results: Mean (±SD) age was 59 (±12) years, 87% were female, and 77% were white. Mean fatigue severity rating was 3.8 (±2.1; range 0-10). Proportion defined as obese ranged from 27% (BMI≥30) to 61% (waist circumference, revised), and mean percent fat was 35.6% (±09.0). In unadjusted analyses, all measure of obesity and body fatness were significantly associated with fatigue (Table). Adjustment for covariates attenuated the relationship of body composition measures with fatigue, but the association persisted.
Conclusion: Obesity appears to play a role in RA fatigue, even after controlling for important covariates such as disease activity, sleep, and depression. Associations found using the revised obesity definitions, which increased the number of individuals classified as obese by 89% (BMI) and 30% (waist circumference), were not substantially different from those found with the standard definitions. Addressing obesity in RA may be part of effective interventions for RA fatigue.
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Table. Associations of body composition measures with fatigue severity |
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Unadjusted |
Adjusted1 |
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% (n) obese |
Beta (95% CI) |
p |
Beta (95% CI) |
p |
|
BMI obese (30 kg/m2) |
27% (37) |
1.2 (0.4, 1.9) |
.003 |
0.5 (-0.2, 1.1) |
.18 |
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BMI obese (revised; 26 kg/m2) |
51% (70) |
1.6 (1.0, 2.3) |
<.0001 |
0.7 (0.1, 1.3) |
.02 |
|
Waist obese (women ≥ 88cm, men ≥ 102 cm) |
47% (63) |
1.3 (0.6, 2.0) |
.0002 |
0.5 (-0. 1, 1.1) |
.11 |
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Waist obese (revised; Women ≥ 83cm, Men ≥ 96 cm) |
61% (82) |
1.3 (0.6, 2.0) |
.0004 |
0.6 (-0.02, 1.2) |
.06 |
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Total % fat |
|
1.4 (0.7, 2.1) |
.0002 |
0.3 (-0.06, 0.7) |
.10 |
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1Adjusted for RADAI, PHQ, HAQ, self-reported sleep quality, age, sex, RA duration. |
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* Katz, presented at ACR/ARHP, 2011.
Disclosure:
P. P. Katz,
None;
V. Chernitskiy,
None;
M. Margaretten,
None.
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