Incidence and prevalence of ankylosing spondylitis in Finland

Abstract

Objective: To determine the incidence and prevalence of clinically significant ankylosing spondylitis (AS) in Finland.

Methods: The incidence study covered patients entitled under the nationwide sickness insurance scheme to receive specially reimbursed medication for AS in 5/21 central hospital districts in Finland (population base about one million adults > or = 16 years of age) in 1980, 1985, and 1990. The prevalence study covered a representative sample of the Finnish population > or = 30 years of age, initially comprising 8000 persons, of whom 7217 participated in the field survey carried 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 encountered 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 population based data on the incidence and prevalence of clinically significant AS in Finland. The incidence rates of AS remained similar for the 3 study years.