Kanji Shichikawa

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

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.

Older age onset rheumatoid arthritis with or without osteoarthritis

The clinical features of a group of 79 patients with older age onset rheumatoid arthritis (ORA) were compared with those of a group of 414 patients with younger age onset rheumatoid arthritis. The ORA group contained approximately equal numbers of men and women, were less rheumatoid factor positive, had a raised erythrocyte sedimentation rate, lower HLA-DR4 positivity, and a tendency towards larger joint involvement at the onset of the disease. These features have been reported by many authors except for the lower DR4 positivity. Of these features, the lower prevalence of rheumatoid factor positivity and the tendency towards larger joint involvement at the onset were characteristic of a subset of patients with ORA who had had osteoarthritis before the onset of rheumatoid arthritis. It is suggested that osteoarthritic large joints may be susceptible to the occurrence of rheumatoid synovitis at the onset of the disease, but that the osteoarthritis inducing factor may be negatively related to the progression of rheumatoid arthritis.

Increase in age at onset of rheumatoid arthritis in Japan over a 30 year period

OBJECTIVES To determine changes in demographic variables and severity of rheumatoid arthritis (RA) that may have occurred during the 30 year period from 1960 to 1990 in Japan. METHODS Using records of patients diagnosed with RA from two hospitals, demographic and clinical features at initial visit were compared between two groups, one from 1960 to 1965 (group I) and the other from 1985 to 1990 (group II). RESULTS Mean age at the time of onset of the disease increased significantly from 37.5 years in group I to 46.9 in group II. The peak age at onset of RA shifted from the third to the fifth decade between group I and group II. There was no obvious change in morbidity as determined by seropositivity, rheumatoid nodules, and assessments of hip involvement. CONCLUSION The age at onset of RA was delayed during a recent 30 year period in Japan. This increase in age at onset might result from environmental changes that occurred in Japan or may reflect a birth cohort phenomenon. Improvement of severity of disease was not found in this study.

Increased rate of hysterectomy in women undergoing surgery for osteoarthritis of the knee

We performed a case-controlled study to determine whether previous gynecological surgery is associated with severe osteoarthritis (OA) of the knee, the hip or the spine, as well as mild OA of the knee. Patients who underwent surgical treatment for OA were defined as having severe OA. Patients with knee pain and radiographic grade 2 OA in a tibiofemoral joint on the Kellgren and Lawrence scale were defined as having mild knee OA. An increased rate of hysterectomy was observed in the severe knee OA group after adjustment for age and number of children, or even after adjustment for body mass index. Hysterectomy in this group was most often performed for myoma uteri. Patients with mild knee OA tended to have previous hysterectomy. From the results, we speculate that certain subsets of OA which often take a progressive course might be related to hysterectomy.