Very low prevalence of hip osteoarthritis among Chinese elderly in Beijing, China, compared with whites in the United States - The Beijing Osteoarthritis study

Objective. To compare the prevalence of osteoarthritis (OA) of the hip among elderly persons in China and the US.. Methods. We recruited a population-based sample of 1,50,15 persons (82% of those enumerated) ages greater than or equal to60 years living in Beijing, China. Subjects answered questions about joint symptoms and underwent radiography of the pelvis. Radiographs of the Beijing subjects were intermingled with hip radiographs of white women ages greater than or equal to65 years from the Study of Osteoporotic Fractures (SOF) and white men and women ages 60-74 years from the First National Health and Nutrition Examination Survey (NHANES-I) and were then interpreted. Radiographic hip OA was defined as the presence of 1 of the following 3 findings in either hip: minimum joint space of less than or equal to1.5 mm, definite osteophytes and joint space narrowing, or greater than or equal to3 radiographic features of OA. Symptomatic hip OA was defined as both radiographic OA and hip pain. Results. The crude prevalence of radiographic hip OA in Chinese ages 60-89 years was 0.9% in women and 1.1% in men; it did not increase with age. Chinese women had a lower age-standardized prevalence of radiographic hip OA compared with white women in the SOF (age-standardized prevalence ratio 0.07) and the NHANES-I (prevalence ratio 0.22). Chinese men had a lower prevalence of radiographic hip OA compared with white men of the same age in the NHANES-I (prevalence ratio 0.19). There were no cases of symptomatic hip OA in the Chinese men and only 1 case in the Chinese women; 35 cases were expected in both sexes. Conclusion. This is the first population-based study of hip OA in China to use standardized radiographic methods and definitions. We found that hip OA was 80-90% less frequent than in white persons in the US. Identification of the genetic and environmental factors that underlie these differences may help elucidate the etiology and prevention of hip OA.