BMI mediates pain severity in hands, lower extremities in patients with hand OA

In patients with hand osteoarthritis (OA), the higher the body mass index (BMI), the more severe the pain in the hands, feet, and knees/hips is, according to a study. The generalized pain experienced by overweight or obese OA patients may be attributed to low-grade inflammation.

The study included 281 hand OA patients (median age 61 years, 89 percent female). Researchers measured hand pain with the Australian/Canadian Osteoarthritis Hand Index (AUSCAN; range 0–20) and Numerical Rating Scale (NRS; range 0–10), foot pain with the NRS (range 0–10), knee/hip pain with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC; range 0–20), painful total body joint count, and pain sensitization.

Overall, the patients experienced a wide range of pain intensity in the hands, feet, and knees/hips, with the highest pain intensity in the hands. Of the patients, 95 (34 percent) were overweight and 60 (21 percent) were obese. Higher BMI correlated with higher levels of inflammatory biomarkers, namely tumour necrosis factor (TNF), interleukin (IL)-6, IL-1Ra, resistin, leptin, and high-sensitivity C-reactive protein (hsCRP).

In the analyses, each 5-unit increase in BMI was associated with more severe hand pain (average increase in AUSCAN, 0.64, 95 percent confidence interval [CI], 0.23–1.08), foot pain (average increase in NRS, 0.65, 95 percent CI, 0.36–0.92), knee/hip pain (average increase in WOMAC, 1.31, 95 percent CI, 0.87–1.73), generalized pain, and pain sensitization.

Of note, the effects of BMI on hand pain and painful total body joint count were partially mediated by leptin and hsCRP, respectively. Effect sizes for mediation by leptin were larger for the hands than for the lower extremities and were statistically significant for the hands only.