When the researchers performed mediation analyses, they found the effects of BMI on hand pain and painful total body joint count were partially mediated by leptin and hsCRP, respectively. This finding is consistent with a previous meta-analysis, which found a significant correlation between levels of hsCRP and joint pain.5 However, the effects of BMI on measures of central pain sensitization did not appear to be mediated through hsCRP or any of the other inflammatory biomarkers, including leptin. The data also suggest that none of the inflammatory biomarkers mediated the association between BMI and the presence of widespread pain.
“We measured a large number of inflammatory biomarkers in serum/plasma to explore whether the observed associations between BMI and pain could be explained by systemic low-grade inflammation,” says Dr. Gloersen. “To our surprise, the majority of the inflammatory biomarkers did not mediate the association between BMI and pain, suggesting systemic low-grade inflammation mediates this association to a lesser extent than what we hypothesized before conducting the study. However, [because] we looked at each biomarker separately, we cannot rule out that combinations of certain biomarkers in the mediation analyses could have led to different results.”
The researchers found the effect sizes for mediation by leptin were larger for the hands than for the lower extremities and were statistically significant for only the hands.
“We believe the role of leptin is more important in the hands than in the lower extremities, due to the biomechanical effects of obesity being the dominating mechanism behind the observed association between BMI and pain in the lower extremities,” says Dr. Gloersen. “In contrast to the knee and hip joints, the hand joints are non-weight bearing, and the systemic effects of obesity may, thus, play a more important role in the association between BMI and hand pain.”
Lara C. Pullen, PhD, is a medical writer based in the Chicago area.
References
- Gloersen 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 an observational cohort of hand osteoarthritis patients. Arthritis Rheumatol. 2022 May;74(5):810–817.
- Cimmino MA, Scarpa R, Caporali R, et al. Body mass and osteoarthritic pain: Results from a study in general practice. Clin Exp Rheumatol. 2013 Nov–Dec. 31:843–849.
- Ding H, Solovieva S, Leino-Arjas P. Determinants of incident and persistent finger joint pain during a five-year followup among female dentists and teachers. Arthritis Care Res (Hoboken). 2011 May;63(5):702–710.
- Visser M, Bouter LM, McQuillan GM, et al. Elevated C-reactive protein levels in overweight and obese adults. JAMA. 1999 Dec 8;282(22):2131–2135.
- Jin X, Beguerie JR, Zhang W, et al. Circulating C-reactive protein in osteoarthritis: a systemic review and meta-analysis. Ann Rheum Dis. 2015 Apr;74(4):703–710.
