Total incidence and distribution of inflammatory joint diseases in a defined population: results from the Kuopio 2000 arthritis survey.

Abstract

OBJECTIVE: To study the incidence of inflammatory joint diseases in a defined population in Finland. METHODS: We collected data for the year 2000 on a population of 87,000 inhabitants of Kuopio, Finland, of whom 20% were < 16 years of age. Information about the study was given through a local newspaper, and subjects attended one health center and 2 local hospitals for study. Inclusion criteria were that subjects have at least one peripheral joint with synovitis or signs of inflammation in sacroiliac, glenohumeral, or hip joints on the first visit. Incidence rates were calculated according to the diagnosis on the first visit, except for children, for whom diagnoses were established after 3 months' followup. RESULTS: A total of 188 adult incident cases (138 women, 50 men) and 11 children (8 girls, 3 boys) satisfied the inclusion criteria. The incidence of all arthritides was 230/100,000 (95% confidence interval 198.9-263.9) for the whole population; 271/100,000 (95% CI 233.7-312.7) for adults and 64/100,000 (95% CI 31.7-113.8) for children. Among adults the annual incidence of rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis (ReA), other spondyloarthropathies (SpA), connective tissue disease (CTD), crystalline arthritis, viral arthritis, and undifferentiated arthritis were 36, 7, 23, 10, 13, 9, 19, 7, and 149/100,000, respectively. The mean age at diagnosis was 49.4 +/- 16.3 years for all cases of arthritis among adults, about the same for both women and men. The mean age at diagnosis was 59.7 years in RA, 31.5 years in AS, 48.7 years in PsA, 38.0 years in ReA, 36.5 years in other SpA, 36.1 years in CTD, 65.0 years in crystalline arthritis, 53.3 years in viral arthritis, and 48.3 years in undifferentiated arthritis. Four of 11 children had juvenile idiopathic arthritis (JIA). The incidence of JIA was 23/100,000 in the population < 16 years of age. Of the remaining cases, 3 children had antibodies against Sindbis (Pogosta) virus and 4 had a transient monoarthritis. CONCLUSION: The overall incidence of arthritides among adults was slightly higher than previously reported from Finland. The incidence rates in the child population are in agreement with previous figures. These data are useful in planning the provision of health care.