Ankylosing spondylitis in Rochester, Minnesota, 1935-1989. Is the epidemiology changing?
Carbone LD., Cooper C., Michet CJ., Atkinson EJ., O'Fallon WM., Melton LJ.
OBJECTIVE: To determine trends in the incidence and clinical presentation of ankylosing spondylitis first diagnosed between 1935 and 1989 among residents of Rochester, Minnesota, and in the survival of the patients. METHODS: Population-based descriptive study. RESULTS: The overall age- and sex-adjusted incidence rate was 7.3 per 100,000 person-years (95% confidence interval 6.1-8.4). The rate tended to decline between 1935 and 1989, but there was little change in the age at symptom onset or diagnosis over the 55-year study period. Overall survival was not decreased up to 28 years following diagnosis. CONCLUSION: These data indicate that there is a constancy in the epidemiologic characteristics of ankylosing spondylitis and suggest that previously study results indicating changes may have been due to biases in patient selection and study design.