Epidemiology
Abstract #946 Risk Factors for Severe Hip Osteoarthritis in a Large Female Cohort Study E Karlson, L Mandl, F Grodstein, O Sangha, M Liang, F Speizer. Boston and Munich.
Objective: To examine the relationship of age, body mass index and physical activity to the development of hip osteoarthritis.
Method: The investigators studied this relationship in the Nurses Health Study, a prospective cohort study assembled in 1976 and composed of 121,700 women.
Results: 567 women underwent total hip replacement, due to end-stage hip arthritis attributed to underlying osteoarthritis. Older age was related to greater incidence of hip osteoarthritis. Similarly, weight was a positive risk factor. In particular, there was a 2.5-fold greater risk [RR = 2.6; 95% CI 1.7-3.9] of incident hip osteoarthritis among the heaviest women [body mass index > 35 kg/m2] compared to the leanest women at entry. Early obesity was particularly strongly related to risk, with a greater than five-fold greater risk among the heaviest, compared to the leanest, women at age 18. In contrast, physical activity and hormone use were not related to the development of hip osteoarthritis.
Editorial Comments:Whereas previous studies have yielded conflicting results regarding the relationship of body weight to hip osteoarthritis, these data provide strong evidence that obesity, particularly in young adult life, is an important risk factor for hip osteoarthritis in women.
Abstract #1994 (A) Varus-Valgus Alignment in the Progression of Knee Osteoarthritis L Sharma, E Shamiyeh, D Felson, S Cahue, D Dunlop. Chicago and Boston.
Objective: To determine if varus-valgus alignment is related to progression of knee osteoarthritis.
Method: The relationship of joint alignment to the course of knee osteoarthritis was prospectively examined among 240 patients with knee osteoarthritis recruited from the community. Radiographic evidence of knee osteophytes and symptoms was assessed at baseline and at 18 months of follow-up.
Results: The progression of medial tibiofemoral joint space narrowing occurred in 28 of 94 varus knees versus 9 of 106 non-varus knees. Similarly, valgus knees demonstrated greater progression of lateral tibiofemoral joint space narrowing, occurring in 19 of 91 valgus knees versus 7 of 109 non-valgus knees. Varus alignment at baseline was associated with a greater than 3-fold [RR 3.65; 95% CI 1.57-8.52] greater progression of medial compartment narrowing, as did valgus alignment at baseline relate to a greater than 3-fold [RR 3.85; 95% CI 1.54-9.63] greater progression to lateral joint space narrowing. The increased risk of progression, for both varus and valgus alignment at baseline, persisted after adjustment for age, bony mass index and varus-valgus laxity.
Editorial Comments:These investigators have identified a novel risk factor for progression of joint space narrowing in patients with knee osteoarthritis. These findings further support the growing body of work from this laboratory, that varus and valgus alignment is an important consideration in the prevalence and progression of knee osteoarthritis.
Abstract #633 (A) Gender and Ethnic Differences in Radiographic Knee and Hip OA J Jordan, J Renner, G Luta, A Dragomir, M Hochberg, C Helmick. North Carolina, Maryland, Georgia.
Objective:To determine whether ethnic difference in the prevalence of knee and hip osteoarthritis exist between African Americans and Caucasians.
Method: The investigators studied the prevalence of knee an hip osteoarthritis in The Johnston County Osteoarthritis Project.
Results: In this community-based study of 3,145 people, the population is one-third African American and two-thirds female. With regard to hip osteoarthritis, there were no differences between the African American and Caucasian women. However, the African American men were 35% more likely to have radiographic hip osteoarthritis than their Caucasians counterparts. At the knee joint, the African American women possessed more knee osteoarthritis than the Caucasian women, but these differences did not persist after adjustment for age, body mass index and education. African American men were at greater risk of having more severe knee osteoarthritis than their Caucasian counterparts [relative risk 2.64; 95% CI 1.59-4.38].
Editorial Comments:Ethnic differences, between African Americans and Caucasian Americans, in the prevalence of knee and hip osteoarthritis exist among men in The Johnston County Study, but not among women.
Abstract #632 (A) Comparison of knee osteoarthritis prevalence between Chinese in Beijing and Caucasian in U.S. Y Zhang, L Xu, M Nevitt, P Aliabadi, W Yu, L Lui, DT Felson. Boston, China, and San Francisco.
Objective: To determine if racial difference in the prevalence of knee osteoarthritis exists between Chinese living in Beijing and Caucasian Americans.
Method: Beijing residents were recruited door-to-door in randomly selected neighborhoods. These Chinese participants underwent the same inquiry regarding joint symptoms and same radiographs as the Caucasian Americans living in Framingham, MA.
Results: Among the Chinese participants, the prevalence of knee osteoarthritis increased with age. Radiographic knee osteoarthritis was more common among the Chinese (49%) compared to the Caucasian (35%) women [relative risk 1.95; 95% confidence interval 1.5-2.4]. The prevalence of knee osteoarthritis was reversed among the men, with a 25% prevalence among Chinese, relative to 35% among Caucasian, men [relative risk 0.7; 95% confidence interval 0.5-0.9]. These proportions were observed after taken the age distribution of the populations into account.
Editorial Comments: The prevalence of knee osteoarthritis is increased among Chinese relative to Caucasian women, despite the fact that Chinese women are thinner than Caucasian American women and that obesity is a major risk factor for osteoarthritis in the United States. In men, the prevalence of knee osteoarthritis is reversed, being lower in the Chinese living in Beijing compared to the Caucasian men living in Framingham. Factors other than weight that might explain the observed racial differences are not known.
