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The relative contribution of mechanical stress and systemic processes in different types of osteoarthritis: the NEO study

2014; Elsevier BV; Volume: 22; Linguagem: Inglês

10.1016/j.joca.2014.02.387

1522-9653

Annemieke Visser, Renée de Mutsert, Saskia le Cessie, Martin den Heijer, F.R. Rosendaal, M. Kloppenburg, NONU-HIP study group,

Infrared Thermography in Medicine

Purpose: Obesity is a risk factor for osteoarthritis (OA) in both weight-bearing and non-weight-bearing joints. In the association between obesity and OA, both increased mechanical stress and systemic processes seem to be of importance, although it is unclear which mechanisms play a role in certain joints. To gain more insight into the relative contribution of mechanical stress and systemic processes to OA of weight-bearing and non-weight-bearing joints, we examined the association of surrogates for both mechanisms with OA of the knees, hands or both. Methods: The Netherlands Epidemiology of Obesity (NEO) study is a population-based cohort including 6673 lean, overweight and obese participants aged 45–65 years. Weight (kg) and fat mass (kg) were measured, fat free mass (FFM) (kg) was calculated. The metabolic syndrome (MetS) was defined following the ATPIII criteria; based on measured waist circumference (cm), blood pressure (mmHg), triglycerides (mmol/L), HDL cholesterol (mmol/L), fasting glucose (mmol/L), and recorded medication use. Knee and hand OA were defined according to the ACR clinical criteria; pain and stiffness were measured using a standardized questionnaire, physical examination of the knees and hands was performed by trained research nurses. Odds ratios (OR) with 95% confidence intervals (CI) were calculated to associate surrogates for mechanical stress (weight, FFM) and systemic processes (MetS) with OA in knees alone, both knees and hands or hands alone, using individuals without knee or hand OA as reference group. Analyses were adjusted for age, sex, height, smoking, education and ethnicity, and either metabolic factors or weight. Finally, adjusted ORs were calculated for each OA type in three weight categories ( 90 kg), stratified by MetS. Participants in the lowest weight category without MetS served as reference. Results: After exclusion of participants with missing data (n = 45), data from 6628 participants were analyzed (median (IQR) age 56 years (50–61), BMI 26 kg/m2 (23–28), 56% women). The estimated population prevalence of knee, both knee and hand, and hand OA were 10%, 4% and 8%, respectively. After adjustment for metabolic factors, knee OA was associated with both weight (OR 1.49 (95%CI 1.32,1.68)) and FFM (OR 2.05 (1.60,2.62)). Similar results were observed for OA in both knees and hands (OR 1.51 (95%CI 1.29,1.78) and 2.17 (1.52,3.10) respectively). Neither knee OA nor OA in both knees and hands were associated with MetS after adjustment for weight (OR 1.08 (95%CI 0.85,1.39) and (1.03 (0.72,1.46) respectively). In hand OA the opposite was observed; whereas no associations with weight and FFM were observed after adjustment for metabolic factors (OR 1.12 (95%CI 0.96,1.32) and 1.17 (0.83,1.63) respectively), hand OA remained associated with MetS, after adjustment for weight (OR 1.46 (95% CI 1.06,2.02)). The figure illustrates the relative contribution of weight as surrogate for mechanical stress and MetS as surrogate for systemic processes to OA of the knees (a) and hands (b). The adjusted ORs for knee OA were higher in higher categories of weight as compared with the lowest weight category. The adjusted OR of the highest weight category in individuals without MetS was 2.62 (95%CI 1.77,3.88) (Figure). The adjusted OR of highest versus lowest weight category in individuals with MetS was 2.30 (1.29,4.12). The presence of MetS, adjusted for the weight categories, did not result in a higher OR for knee OA (1.16 (95%CI 0.91,1.47)) (Figure). The same was observed in relation to OA in both knees and hands. In hand OA on the contrary, the ORs were not associated with weight. The adjusted OR of highest versus lowest weight category was 1.40 (95%CI 0.89,2.21) in individuals without MetS (Figure), and 0.77 (0.39,1.51) in individuals with MetS. MetS on the other hand was associated with hand OA, adjusted for the weight categories; individuals with MetS had a higher OR for hand OA as compared to individuals without MetS (1.52 (95%CI 1.10,2.09)) (Figure). Conclusion: This study suggests that in knee OA, whether or not in co-occurrence with hand OA, mechanical stress is the most important underlying mechanism, whereas in hand OA alone, systemic processes might contribute most.