For patients with hand osteoarthritis (OA), pain severity in feet, knees, and hips was associated with increased body mass index (BMI). These findings were published in Arthritis & Rheumatology.
This analysis sourced data from the observational cohort study Nor-Hand, conducted from 2016-2017 in Norway. Patients (N=281) with hand OA were assessed for pain severity using a 10-point Numerical Rating Scale (NRS), the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) pain subscale, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale, they underwent quantitative sensory testing, and were evaluated for biomarkers of inflammation.
Patients were aged median 61 (interquartile range [IQR], 57-66) years, 89% were women, mean BMI was 26.5 (standard deviation [SD], 5.0) kg/m2, 34% were overweight, and 21% were obese. Individuals with higher BMI had increased levels of tumor necrosis factor-α, interleukin (IL)-6, IL-1Ra, resistin, leptin, and high-sensitivity-C-reactive protein (hs-CRP).
Every 5.0 kg/m2 increase in BMI had a significant mean total effect of 0.64 (95% CI, 0.23) on AUSCAN score, 0.46 (95% CI, 0.20-0.72) on NRS hand pain, 0.65 (95% CI, 0.36-0.92) on NRS foot pain, 1.31 (95% CI, 0.87-1.73) on WOMAC knee and hip pain, and 1.15 (95% CI, 0.68-1.60) on painful total body joint count.
In addition, BMI had a natural direct effect on NRS foot pain (mean, 0.57), WOMAC knee and hip pain (mean, 1.13), and painful total body joint count (mean, 0.87) and a natural indirect effect on AUSCAN hand pain (mean, 0.39).
A 5.0 kg/m2 increase in BMI had significant total effects on pressure pain threshold (mean, -0.38; 95% CI, -0.64 to -0.12) and temporal summation (mean, 0.27; 95% CI, 0.09-0.45). There was also a significant natural direct effect on temporal summation (mean, 0.23; 95% CI, 0.02-0.45).
There was evidence that leptin had a mediating effect on hand pain and hs-CRP a mediating effect on painful total body joint count.
This study was limited as it was not designed to assess which aspect of the relationship between increased BMI and pain is causal.
These findings suggested that increased BMI had a positive relationship with pain severity in hands, feet, and knees of patients with hand OA. The mediating effect of some inflammatory biomarkers may indicate there are systemic effects of obesity on pain in addition to possible biomechanical effects, however, additional study is needed to evaluate causality.
Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.
Gløersen M, Pettersen PS, 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.Arthritis Rheumatol. Published online February 9, 2022. doi:10.1002/art.42056