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Ann Rheum Dis 1999;58:751-756 doi:10.1136/ard.58.12.751
  • Extended report

Changes in the incidence and prevalence of rheumatoid arthritis in Kamitonda, Wakayama, Japan, 1965–1996

  1. Kanji Shichikawaa,
  2. Koji Inoueb,
  3. Shigenaga Hirotac,
  4. Akira Maedaa,
  5. Hiroshi Otad,
  6. Masami Kimurae,
  7. Toshio Ushiyamab,
  8. Masaki Tsujimotof
  1. aYukioka Hospital, 2–2–3, Ukita Kita-ku,Osaka 530–0021, Japan, bDepartment of Orthopaedic Surgery, Shiga University of Medical Science, Otsu, Shiga, Japan, cDepartment of Orthopaedic Surgery, Hikone Chuo Hospital, Hikone, Shiga, Japan, dTezukayama Hospital, Tezukayama, Abeno-ku, Osaka, Japan, eKimura Clinic, Nishinomiya, Hyogo, Japan, fTsujimoto Clinic, Koryonishimachi, Sakai, Osaka, Japan
  1. Dr K Shichikawa.
  • Accepted 27 July 1999

Abstract

OBJECTIVE To evaluate secular trends in the incidence and prevalence of rheumatoid arthritis (RA) in Japan.

METHODS The incidence and prevalence of RA were determined in a longitudinal population based study in the Kamitonda district, Wakayama, Japan, from 1965 to 1996.

RESULTS In the study area consisting of about 3000 inhabitants, 16 incident cases, satisfying definite RA by the Rome criteria were detected during the study period. The age and sex adjusted incidence in both men and women combined and the age adjusted incidence in women significantly decreased (p<0.025 and p<0.01, respectively). The age and sex adjusted prevalence in all inhabitants tended to decrease (p<0.1), and the age adjusted prevalence in women significantly declined (p<0.025). In men, however, neither incidence nor prevalence showed significant change.

CONCLUSIONS The decline of incidence and prevalence of female RA may be reducible to some environmental changes preferentially occurring more obviously in Japanese women than in men. Because the use of oral contraceptives has been extremely low in Japan, the decline should be explained by other factors.

Footnotes

  • Funding: this study was supported in part by a grant in aid for Scientific Research from the Ministry of Education, Science and Culture of Japan and by a grant from the Ministry of Health and Welfare of Japan.

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