Higher BMI Linked to Greater Pain Severity in Osteoarthritis

A higher body mass index (BMI) was associated with more pain in the hands, feet, knees, and hips in patients with hand osteoarthritis (OA), according to a study published in Arthritis & Rheumatology.¹ Inflammation, as measured by hs-CRP, and the systemic effects of obesity may exacerbate pain levels.

“Overweight and obesity induce a low-grade inflammatory state as adipose tissue produces inflammatory biomarkers, which may affect pain mechanisms,” investigators stated. “Cytokines, such as interleukin (IL)-1β, IL-6 and tumor necrosis factor alpha (TNF-α), may act directly on nociceptive neurons through their receptors or indirectly through induction of prostaglandin production, which may activate or sensitize nociceptive neurons, leading to increased pain.”

Information was obtained from 281 participants from Nor-Hand, an observational study of patients with hand OA. Asociations between BMI and hand pain determined by the Australian/Canadian Osteoarthritis Hand Index (AUSCAN), Numerical Rating Scale (NRS), foot pain by NRS, painful total body joint count, pain sensitization, and the Western Ontario/McMaster Universities Osteoarthritis Index (WOMAC). Natural-effects models analyzed direct and indirect effects of BMI on pain via biomarkers.

Eligible patients were between 40 and 70 years old and had rheumatologist-diagnosed hand OA, which was also evaluated using the American College of Rheumatology (ACR) criteria. BMI and Pressure pain threshold (PPT) were calculated during a physical examination. Temporal summation (TS), a sign of central pain sensitization, was assessed with 7 weighted punctuate probs. Serum was examined for high-sensitivity C-reactive protein (hs-CRP) and matrix metalloproteinase-dependent degradation of C-reactive protein (CRPM).

Data, such as age, sex, education levels, physical activity, sleep, smoking status, anxiety and depression, and pain were assessed to account for possible confounders.

Patients who were overweight or obese were seen in 34% (n = 95) and 21% (n = 60), respectively. Inflammatory biomarkers, such as TNF-a, IL-6, IL-1Ra, leptin, and hsCRP were higher in patients with a higher BMI. A 5-unite increase in BMI was linked to more severe pain in the hands (increased AUSCAN by 0.64, 95% CI: 0.23-1.08), feet (increased NRS by 0.65, 95% CI: 0.36-0.92), knees and hips (increased WOMAC by 1.31, 95% CI: 0.87-1.73), and generalized pain and sensitization.

A larger waist circumference was reported in patients with more pain. Although borderline statistically significant, painful total body joint count was partially mediated through hs-CRP for those with a larger waist circumference. BMI effects on both hand pain and total body joint counts were partially mediated by leptin and hs-CRP. These effects were greater in the hands than in the lower extremities, with significant difference shown in the hands. Those with a higher BMI had lower PPTs and greater TS, indicating more central pain sensitization.

Causality and reverse causation could not be determined due to the cross-sectional study design and unmeasured variables may have created biased results. Generalizability may be limited, as patients with OA from secondary care may have more pain that those in primary care. However, as patients were not required to fulfill ACR hand OA criteria, those with milder disease severity were still included in the study.

“Despite modest strengths of associations, our results suggest that weight loss may be a strategy to prevent or treat pain in people with hand OA, which should be further explored in future studies,” investigators concluded.

Reference:

Gløersen M, Steen Pettersen P, Neogi T, et al. Associations of body mass index with pain and the mediating role of inflammatory biomarkers in hand osteoarthritis: Results from the Nor-Hand study [published online ahead of print, 2022 Feb 9]. Arthritis Rheumatol. 2022;10.1002/art.42056. doi:10.1002/art.42056