INCIDENCE AND PREVALENCE OF HUNTINGTONS-DISEASE IN OLMSTED COUNTY, MINNESOTA (1950 THROUGH 1989)

Objective: To calculate average annual incidence rates for Huntington' s disease (HD) from 1950 through 1989 and to estimate prevalence rates of the disease for January 1, 1960, and January 1, 1990. Design: Heal th care records from all sources, including hospitals, outpatient clin ics, and long-term care institutions, are readily available for all in habitants of Olmsted County, Minnesota. The diagnoses entered in these records have been coded and indexed. All health care records containi ng a diagnosis that might suggest HD were reviewed, and those patients for whom the symptoms of HD began between January 1, 1950, and Decemb er 31, 1989, were identified. We used specific criteria for diagnosing HD. Participants: Health care records were reviewed; residence in Olm sted County during the year of symptom onset was required. Main Outcom e Measures: Average annual incidence rates and prevalence rates for Ja nuary 1, 1960, and January 1, 1990. Results: Overall incidence rates w ere 0.4 (95% confidence interval I[I], 0.1 to 0.8) for women and 0.2 ( 95% CI, 0.04 to 0.6) for men per 100 000 person-years. Estimated preva lence rates for January 1, 1960, per 100 000 person-years were 6 (95% CI, 0.7 to 21.5) for women and 6.6 (95% CI, 0.8 to 23.8) for men. For January 1, 1990, the prevalence rates were 1.8 (95% CI, 0.04 to 10.2) for women and 2 (95% CI, 0.05 to 10.9) for men. Conclusions: Incidence and prevalence rates of HD in this community are similar to those rep orted in other communities. The small numbers of affected persons do n ot allow an estimate of variation over time.