title: The national burdens of rheumatoid arthritis and osteoarthritis in Japan: projections to the year 2010, with future changes in severity distribution.
abstract: Abstract We projected the national burdens of rheumatoid arthritis (RA) and osteoarthritis (OA) in Japan in the year 2010, together with future changes in severity distribution. The age-, sex-, and in/outpatient-specific prevalence rates of RA and OA from the 1999 National Patient Survey were multiplied by the National Census population projections for 2000 and 2010. The years lived with disability (YLD) of RA or OA in 2010 were adjusted for the projected changes in the summed measure of severity distribution (i.e., the sum products of the percentage distribution and the health-related quality of life score for three severity classes) using the corresponding regression equations. Between 2000 and 2010, the numbers of patients with RA and OA in Japan will increase by 14% (from 0.31 million to 0.36 million) and 27% (from 0.77million to 0.98 million), respectively, and accordingly, the YLD of RA and OA will increase by 3% (from 42.8 to 43.6 per 100 000) and 21% (from 65.8 to 79.1 per 100 000), respectively. Because of the decreasing proportion of severely affected patients, the increase in YLD may be smaller compared with the increase in the number of patients. As in other developed countries, the national burdens of RA and OA in Japan will increase between 2000 and 2010. However, any projection is likely to be an overestimate unless it considers future changes in the severity distribution associated with medical progress.
authors.affiliation: Department of Preventive Medicine, St. Marianna University School of Medicine , 2-16-1 Sugao, Miyamae-ku, Kawasaki 216-8511 , Japan.
authors.forename: Machi
authors.initials: M
authors.lastname: Suka
authors.forename: Katsumi
authors.initials: K
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Izuno