[Epidemiology of bone and joint disease - the present and future - . Epidemiology of lumbar spondylosis in Japan : the ROAD study].

To clarify the prevalence and estimate the number of people with osteoarthritis, and osteoporosis in Japan, we established a large-scale population-based cohort study entitled Research on Osteoarthritis/osteoporosis Against Disability (ROAD). The prevalence of lumbar spondylosis (LS) in men and women was 80.6% and 61.5%, respectively with utilizing the ROAD baseline data. The cumulative incidence of LS in men and women was 15.2%/y and 10.4%/y, respectively with using the follow-up data. The estimated number of prevalent cases and incident cases/y of LS in Japan was approximately 38 million and 9 million, respectively. Older age, male-sex, and greater BMI were associated with the occurrence of LS.