Incidence of chronic inflammatory joint diseases in Finland in 1995

To investigate trends in the incidence of chronic inflammatory joint diseases.

Subjects entitled to receive drug reimbursement for chronic inflammatory joint diseases in 5/21 central hospital districts (population base about 1 million adults) in Finland during 1995 were studied. The mean age at disease onset was compared with figures from 1975, 1980, 1985, and 1990. Incidence rates were compared with those from 1980, 1985, and 1990.

A total of 710 subjects were entitled to drug reimbursement for chronic inflammatory joint disease that had started at the age of 16 or over. The total incidence was 65/100,000 (95% confidence interval 60.7-70.4); the figures for rheumatoid arthritis (RA), ankylosing spondylitis, psoriatic arthritis, and undifferentiated chronic poly/oligoarthritis were 34, 6, 7, and 13/100,000, respectively. In RA, the mean age at diagnosis was 59.0 years and was the same in rheumatoid factor (RF) positive and RF negative disease. The mean age at diagnosis had increased by 8.8 years from 1975 to 1995 (p<0.001). A 14% decline was evident in the incidence of RA in 1990 and 1995 compared with the earlier years (p = 0.013). In the younger age groups (35-54 years), the incidence declined by 50% compared with the year 1980. The incidence of spondyloarthropathies remained similar during 1980-95.

Continuous monitoring of sickness insurance data provides information on the epidemiology of inflammatory joint diseases that will be useful in assessing demand for and supply of health services.