Changes in the incidence of juvenile rheumatoid arthritis in Finland - PubMed (original) (raw)

Objective: To study trends in the incidence of juvenile rheumatoid arthritis (JRA).

Methods: The study covered subjects who were entitled under the nation-wide sickness insurance scheme to receive specially reimbursed medication for juvenile rheumatic diseases in 11 of 21 central hospital districts in Finland (the base population comprised about 445,000 children <16 yr of age) in 1995. Data from the years 1980, 1985 and 1990 were compared with data from 1995 concerning the central part of the area, which had been included in a previous study by us.

Results: A total of 87 incident cases (58 girls and 29 boys) satisfied criteria for JRA in 1995 in the study area. The incidence of JRA was 19.5 per 100 000 [95% confidence interval (CI) 15.6-24.1] of the population <16 yr of age for the whole area. It was 22.7 per 100,000 (95% CI 17.3-29.2) for the area that had been covered by the earlier study (five districts) and 14.9 per 100,000 (95% CI 9.8-21.7) for the new area (six additional districts). The incidence of JRA was significantly higher than in the earlier years (1980, 1985 and 1990) in the same district (trend, P=0.024). The highest incidence, 60.3 per 100,000 (95% CI 35.8-95.4), was noted in 1995 among girls in the age group 10-15 yr in the southernmost part of the study area.

Conclusions: There was both temporal and regional variation in the incidence of JRA. Results of the present study suggest that environmental factors may influence the frequency of JRA.