[Epidemiology of osteoarthritis in Japan : the ROAD study].

The present study investigated the prevalence of knee osteoarthritis (KOA) and lumbar spondylosis (LS) in the Japanese population, by using a large-scale population-based cohort study named ROAD (Research on Osteoarthritis÷osteoporosis Against Disability) . In men and women aged more than 40 years, the prevalence of KOA was 42.6% and 62.4%, respectively, and that of LS was 81.5% and 65.5%, respectively. A total of 25,300,000 people (8,600,000 men and 16,700,000 women) aged more than 40 years could possibly be affected by KOA, and 37,900,000 people (18,900,000 men and 19,000,000 women) by LS. In addition, our study confirmed that factors such as obesity and occupational activities were associated with both KOA and LS. Nutritional factors (vitamin K) were also associated with KOA. The incidence of KOA is significantly related to the increase in the number of metabolic syndrome components such as overweight, hypertension, dyslipidaemia, and impaired glucose tolerance. Finally, we investigated the usefulness of evaluating neuromuscular indices such as hand-grip strength and walking time for predicting the occurrence of a disability.