Arthritis News – 2002
Influence of obesity on the development of Osteoarthritis of the Hip: A Systematic Review
Summary written by Kevin Fontaine, Ph.D.
Osteoarthritis of the hip (hip OA) is a debilitating disease and a major cause of morbidity, especially among older adults. Some studies estimate that up to 25% of adults aged 55 or older suffer from hip OA. Obesity has been identified as a risk factor for OA of the knee and hands/wrists. However, data on the association between obesity and hip OA is less clear, with some studies suggesting that obesity is a risk factor for developing hip OA, while other studies do not find such an association. To address this issue, Lievense and colleagues (Rheumatology (Oxford) 2002; 41: 1155-1162) conducted a systematic review of the literature to evaluate whether or not obesity associates with hip OA and, if so, how strong that association is.
Methods: To identify relevant observational studies, biographical databases (e.g., Medline) from 1966 through April 2000 were searched. Articles describing studies of the obesity-hip OA association were selected. Identified studies were assessed for methodological quality using standardized techniques.
Results: Of the 2,921 references identified, only 12 articles met selection criteria. The main reason studies were excluded was because no specific information about the obesity-hip OA was provided or because the study design was inappropriate to address the research question (e.g., case report, no control group). Of the 12 studies used, 9 provided useable outcome data. Of those, 7 showed a positive association between obesity and hip OA (average odds ratio (OR) = 1.25). No studies reported a negative obesity-hip OA association. Three of the studies showed a dose-response relationship. That is, the magnitude of the association between obesity and hip OA increased at increased levels of body mass index (BMI). There was no evidence of a differential association between obesity and unilateral or bilateral hip OA. Finally, the association between obesity and hip OA was strongest when clinical symptoms of hip OA were used as outcomes as opposed to X-ray evidence.
Conclusions: Based on the available evidence, there is a moderate positive association between obesity and the development of hip OA.
Editorial Comments: Obesity is a major risk factor for the development of OA, especially knee OA and OA of the hands/wrists. This study, a careful quantitative synthesis of research studies over the past 35 years, indicates that obesity associates moderately with the development of hip OA. Specifically, obese persons are roughly 25% more likely to have hip OA than their non-obese counterparts. This association is considerably weaker than the obesity-knee OA association (i.e., obese persons are approximately 300 to 400% more likely to have knee OA than non-obese persons). Interestingly, however, obesity was more strongly associated with clinical evidence of hip OA than with X-ray evidence. This suggests that excess weight and biomechanical strain on the hip joint may provoke pain and symptoms even in the absence of X-ray manifestations of OA. Additional research is needed both to shed light on the causes of obesity-hip OA association, as well as to investigate whether weight loss reduces pain and improves functioning in persons with hip OA.