Combined associations of obesity and physical activity with pain, fatigue, stiffness, and anxiety in adults with spondyloarthropathies: UK Biobank study

Objective Inflammatory spondyloarthropathies (ISpAs) are associated with pain, fatigue, stiffness, and anxiety. The National Institute for Care and Excellence (NICE) and the European Alliance of Associations for Rheumatology (EULAR) provide limited lifestyle guidance for managing symptoms with ISpAs. We investigated the combined associations of obesity and physical activity with symptom severity in ISpAs. 

Methods The relationship between BMI, physical activity, and symptom severity (spinal and general pain, fatigue, anxiety, mobility) was examined in people with ISpAs (n = 1,577). BMI categories were normal weight (18·5-24·9 kg/m2), overweight (25·0-29·9 kg/m2), and obese (≥30 kg/m2). Physical activity was assessed via the International Physical Activity Questionnaire (low<600 metabolic equivalent of task (MET)-min/week, moderate≥600METs, high≥3000METs). Statistical models adjusted for confounders, including medication, estimated the likelihood (odds ratios; OR) of higher symptom severity across BMI and physical activity categories. 

Results Overweight and obesity, compared to normal weight, were linked to higher severity of all symptoms, with stronger associations for obesity (OR ≥ 2·34, P < 0·001) than overweight (OR ≥ 1.37, P ≤ 0·032). Moderate activity, compared to low, was associated with lower severity of all symptoms (OR ≤ 0·77, P ≤ 0·032). High activity, compared to low, was associated with lower severity of fatigue, anxiety, and mobility issues (OR ≤ 0·74, P ≤ 0·029), but associations with spinal and general pain were not significant (OR ≤ 0·80, P ≥ 0·056). No BMI-by-physical activity combinations were detected, indicating physical activity benefits all BMI groups to a similar extent. 

Conclusion NICE and EULAR guidance for ISpAs should emphasise maintaining a normal weight. Moderate physical activity is optimal for reducing symptom severity and should be promoted in lifestyle guidance.