Association of Change in Body Mass Index With Incidence and Progression of the Structural Defects of Hip Osteoarthritis: Data From the Osteoarthritis Initiative and the Cohort Hip and Cohort Knee study.

OBJECTIVE:To define the association between change in body mass index (BMI) and the incidence and progression of structural defects of hip osteoarthritis as assessed by radiography. METHODS:We used data from 2 independent cohort studies: the Osteoarthritis Initiative (OAI) and the Cohort Hip and Cohort Knee (CHECK) study. Our exposure was change in BMI from baseline to 4-5 years' follow-up. Our outcomes were the incidence and progression of structural defects of hip osteoarthritis as assessed using a modified Croft grade in OAI and the Kellgren/Lawrence grade in the CHECK study. To study incidence, we created incidence cohorts of hips without definite overall structural defects at baseline (i.e., grade <2) and then investigated the odds of hips having definite overall structural defects at follow-up (i.e., grade ≥2). To study progression, we created progression cohorts of hips with definite overall structural defects at baseline (i.e., grade ≥2) and then investigated the odds of having a grade increase of ≥1 from baseline to follow-up. RESULTS:There was a total of 5,896 and 1,377 hips in the incidence cohorts, and 303 and 129 hips in the progression cohorts for the OAI and CHECK study, respectively. Change in BMI (decrease or increase) was not associated with any change in odds of the incidence or progression of definite structural defects of hip osteoarthritis in either the OAI or CHECK cohorts. CONCLUSION:Weight loss may not be an effective strategy for preventing, slowing, or delaying the structural defects of hip osteoarthritis over 4-5 years.