Session Type: Abstract Submissions (ACR)
Body mass index (BMI) is an important risk factor for knee osteoarthritis (OA), but BMI depends only upon height and weight and gives no insight in underlying causal pathways. The objective of this study was to investigate whether the association of BMI with clinical and structural OA can be explained by the amount of fat mass (FM) and/or skeletal muscle mass (SMM).
Participants of the NEO (Netherlands Epidemiology of Obesity) study, a population-based cohort of individuals aged 45-65 years with a BMI ≥ 27 kg/m2 and a control group with a BMI < 27 kg/m2, were used. BMI was assessed by measured weight and length. FM and SMM were assessed using bioelectrical impedance analysis. Clinical OA was defined according to the ACR criteria; based on self-reported knee complaints and physical examination of the knees. Structural OA was defined based on MR imaging of the right knee, performed on 1.5T (Philips, Best, The Netherlands) using a standard knee protocol. Osteophytes were scored according to the Knee Osteoarthritis Score System in nine compartments. Osteophytes were graded from 0 (absent) to 3 (severe). A total score was calculated for each individual, a score of ≥ 6 was considered as structural OA. Odds ratios (OR) with 95% confidence intervals (CI) were calculated to associate BMI, FM, SMM and the FM/SMM ratio with OA using logistic regression analyses, stratified for sex and adjusted for age.
In 4562 participants (mean age 56 years, 52% women) median (IQR) BMI was 30.3 kg/m2 (28.4-33.1), FM 33.5 kg (27.5-40.8) kg and SMM 28.3 (23.0-33.8) kg. Clinical OA was present in 24% of women and 12% of men. MRI data were available in 1134 participants; structural OA was present in 34% of women and 35% of men. In women and men, BMI was associated with clinical and structural OA. Both FM and SMM were associated with clinical OA, in women ORs were 1.02 (1.01-1.03) and OR 1.05 (1.02-1.08) respectively, and in men; ORs 1.02 (1.01-1.04) and 1.04 (1.01-1.07), respectively. Comparable associations were found with structural OA. Remarkably, in clinical OA the FM/SMM ratio was positively associated with OA (ORs 1.48 (1.13-1.94) and 1.92 (1.20-3.06) in women and men respectively), meaning that a higher FM relative to SMM is unfavorable. In structural OA we found that in multivariate analysis including BMI and FM, the association between BMI and OA disappeared, but the association between FM and OA was unchanged, suggesting that FM is mediating the association of BMI with OA. In multivariate analysis including BMI and SMM, the association of both BMI and SMM with structural OA decreased, suggesting that SMM acts as a partial mediator.
BMI, FM and SMM were associated with structural and clinical OA in both women and men. Further analyses suggest that both FM and SMM are involved in the underlying mechanisms of developing knee OA and associated complaints.
A. W. Visser,
M. den Heijer,
F. R. Rosendaal,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-association-of-fat-mass-and-skeletal-muscle-mass-with-clinical-and-structural-knee-osteoarthritis-the-netherlands-epidemiology-of-obesity-study/