Prevalence of joint pain is higher among women in rural Japan than urban Japanese-American women in Hawaii.

OBJECTIVE: Environmental factors such as farming contribute to the frequency of joint symptoms. The purpose of this study is to explore the possible role of environment (lifestyle), by comparing the prevalence of joint pain between Japanese in a rural farming district in Japan and in urban Hawaii.

SUBJECTS AND METHODS: Current or previous pain at specific joints was surveyed among 222 women in rural Japan and 638 Japanese women in urban Hawaii aged 60-79. The age adjusted prevalence was compared using logistic regression.

RESULTS: The prevalence of pain at one or more joints was approximately 70% in Japan and 50% in Hawaii. The prevalence of knee pain in Japan ranged from 36% at ages 60-69 years to 53% at 70-79 years (mean 41%), whereas knee pain affected only 20% of women in Hawaii in both age groups. The odds ratio (and 95% CI) was 3.2 (2.1, 4.8) for knee pain, and 4.0 (2.2, 7.4) for mid-back pain in Japan, compared with Hawaii. Pain was also significantly more common in Japan at the shoulder, elbow, and ankle, but not at other joints. Women in Japan were shorter and weighed less than in Hawaii. Adjustment for body mass index increased the odds ratios to 4.4 (2.9, 6.8) for knee, and 4.5 (2.4, 8.5) for mid-back pain.

CONCLUSION: Although the potential influence of cultural factors or other sources of bias cannot be ruled out, the large differences in the prevalence of pain at specific joints suggest that environmental factors are probably responsible, because both populations are of similar genetic stock.