Keele Research Repository

Background
Obesity predisposes to a pro-inflammatory state. Studies have reported worse clinical outcomes in patients with inflammatory arthritis who are obese. The relationship between obesity and outcomes in patients with polymyalgia rheumatica (PMR), another common inflammatory rheumatic condition, has not been assessed. We examined this in a cohort study of primary care-recruited patients with PMR.

Methods
The PMR Cohort Study is an inception cohort of patients with incident PMR, recruited from 382 general practices. Self-completed questionnaires at 0, 12, and 24-months captured: (a) PMR-related pain (0-10 numeric rating scale [NRS]); (b) PMR-related stiffness (0-10 NRS); (c) anxiety (GAD7); (d) depression (PHQ8); (e) fatigue (FACIT-Fatigue); (f) function (mHAQ); (g) quality of life (EQ-5D-3L). Height was self-reported at baseline, and weight at baseline, 12 and 24 months. Patients were categorised as underweight (BMI<18.5 kg/m2); normal weight (18.50-24.99 kg/m2); overweight (25-29.99 kg/m2); or obese (≥30 kg/m2). Piecewise, multivariable, multilevel, linear mixed-effects regression models examined relationships between BMI categories and outcomes over time, using restricted cubic spline functions. Adjustments were made for age, sex, prednisolone-use, smoking, and alcohol. Due to few underweight patients (three at 0 months; one at 12/24 months), underweight and normal weight patients were combined, as a single reference group.

Results
652 patients were included (62% female). At baseline, mean age was 72 years, median BMI 26.6 (IQR 24.0-30.2), 34% were normal/under-weight, 40% overweight, and 26% obese. Compared to normal/underweight patients, obese patients had the following significantly poorer outcomes (P<0.05): higher pain scores at 12-months; higher stiffness scores at 12 and 24 months; higher depression levels at 12 and 24 months; worse fatigue at 0, 12 and 24 months; worse function at 12 and 24 months; worse quality of life at 0, and 12 months. BMI changed little over 24 months (25.7% and 25.9% obese at 0 and 24-months, respectively).

Conclusion
Obesity is associated with poorer outcomes in patients with PMR. Consideration should be given to providing weight management support to patients with PMR and obesity. Further research should examine the impacts of weight-based steroid dosing on outcomes.