In patients with rheumatoid arthritis (RA), higher body mass index (BMI) is associated with lower foot health, indicating that future RA research should consider BMI as a possible therapeutic target for improving foot health in this population, according to findings published in the Scandinavian Journal of Rheumatology.
High BMI is prevalent in patients with RA, with a possible effect on foot joints. The aim of this cross-sectional study was to examine possible associations at a single point in time of BMI and foot pain, deformity, functional limitations, and synovitis in patients from the Amsterdam Foot cohort with RA (n=230; mean age, 58±13 years; 80% women). In the regression analyses, the independent variable was BMI and the dependent variables were foot pain, forefoot plantar pressure, foot synovitis, foot-related activity limitations, and foot deformity.
The findings showed that higher BMI was associated with small to modest reductions in many of the studied measures of foot health. The most notable association was that of higher BMI and increased foot pain. With a B value (unstandardized regression coefficient) of 0.12, every 1-point increase in BMI produced a 0.12-increase in pain as measured using a 0-10 numeric rating scale (P =.001).
Higher BMI was also associated with foot-related activity limitations, as measured by the disability subscale of the Foot Function Index, the disability subscale of the Leeds Foot Impact Scale, and the physical functioning subscale of the Western Ontario and McMaster Universities Osteoarthritis Index, but not the 10-Metre Walk Test time. Although BMI was not associated with barefoot-measured plantar forefoot pressure, higher BMI was associated with higher in-shoe measured forefoot pressure.
With respect to gait characteristics, increased BMI was associated with greater contact area and longer heel contact time, but no relationship was found with BMI and total contact time. Finally, although a higher BMI was associated with foot synovitis (P =.009) and midtarsal pain, it was not associated with foot deformity. When BMI was assessed as an ordinal (categoric) variable, the results were similar, except for foot structure. Patients with BMIs in the obese range had significantly lower rates of deformity than those with BMIs in the normal range.
Study investigators concluded that these findings, particularly the associations between higher BMI and increased foot pain and activity limitations, suggest the need for “mechanistic and longitudinal studies, including the effects of interventions.”
Dahmen R, Konings-Pijnappels A, Kerkhof S, et al. Higher body mass index is associated with lower foot health in patients with rheumatoid arthritis: baseline results of the Amsterdam-Foot cohort [published online March 10, 2020]. Scand J Rheumatol. doi:10.1080/03009742.2019.1663920