INCIDENCE AND PREVALENCE OF ANKYLOSING-SPONDYLITIS IN FINLAND

Objective. To determine the incidence and prevalence of clinically sig nificant ankylosing spondylitis (4S) in Finland. Methods. The incidenc e study covered patients entitled under the nationwide sickness insura nce scheme to receive specially reimbursed medication for AS in 5/21 c entral hospital districts in Finland (population base about one millio n adults greater than or equal to 16 years of age) in 1980, 1985, and 1990, The prevalence study covered a representative sample of the Finn ish population greater than or equal to 30 years of age, initially com prising 8000 persons, of whom 7217 participated in the field survey ca rried out in 1978-1980. Results. The annual incidence of AS requiring antirheumatic medication was 6.9/100,000 [95% confidence interval (CI) , 6.0-7.8] adults. Eleven cases of clinically significant AS were enco untered in the prevalence study, corresponding to a prevalence of 0.15 % (95% CI, 0.08-0.27%). The ratio between the prevalence rate and the annual incidence rate was 22. Conclusion. This study provides populati on based data on the incidence and prevalence of clinically significan t AS in Finland. The incidence rates of AS remained similar for the 3 study years.