title: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Medicine, Kuopio University Hospital, Finland.
authors.forename: O
authors.initials: O
authors.lastname: Kaipiainen-Seppanen
authors.forename: K
authors.initials: K
authors.lastname: Aho
authors.forename: M
authors.initials: M
authors.lastname: Heliovaara
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005387:Finland / Q000453:epidemiology; D015796:HLA-B27 Antigen / Q000032:analysis; D006650:Histocompatibility Testing; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012217:Rheumatoid Factor / Q000032:analysis; D013167:Spondylitis, Ankylosing / Q000453:epidemiology* / Q000276:immunology
chemical_list: D015796:HLA-B27 Antigen; D012217:Rheumatoid Factor