STROKE INCIDENCE, PREVALENCE, AND SURVIVAL - SECULAR TRENDS IN ROCHESTER, MINNESOTA, THROUGH 1989

Background and Purpose Trends in stroke incidence and mortality are av ailable from few sites worldwide. The unique nature of the medical car e in patients from Rochester, Minn, has allowed the ascertainment of v irtually all cases of stroke for community residents for the period da ting from 1955. This study updates incidence rates, stroke mortality, radiological imaging availability, and prevalence for stroke and subty pes of stroke though 1989 and evaluates trends since 1955. Methods Med ical records of all residents of Rochester with potential diagnosis of stroke during the 5-year period through December 31, 1989, were scree ned to determine whether the case met the criteria for stroke. The typ e of stroke was determined with the use of all available data. Average annual age- and sex-adjusted incidence rates for stroke and various t ypes of stroke were calculated for 5-year periods from 1955 to 1989. P revalence of stroke was also determined. Poisson regression was used t o better clarify the dependence of stroke incidence on multiple variab les. Cox proportional hazards modeling evaluated trends in short-term and long-term stroke survival. Results We found that 496 incidence cas es of stroke occurred among Rochester residents during 1985 to 1989. T he annual age- and sex-adjusted stroke incidence rate was 145 per 100 000 population, which was virtually unchanged from 1980 to 1984 and 13 % higher than the rate determined in 1975 to 1979. Increasing incidenc e rates compared with the 1970s were noted in all groups aged older th an 54 years and in both sexes. Survival after cerebral infarction was dependent on age and calendar year when trends dating from 1955 were e valuated. The annual incidence rate of intraparenchymal hemorrhage was twice that of subarachnoid hemorrhage. Conclusions Incidence rates fo r stroke have remained at a higher rate than those determined in the 1 970s. Although the occurrence of untreated hypertension has been repor ted to be stable or decreasing, the incidence rate of stroke is higher than those noted during the decline in stroke incidence during the 19 60s and 1970s. In addition to the impact of radiological imaging, incr eased contribution of patients with ischemic heart disease, and the po ssible detection of milder cases of stroke, other factors, which are u ndefined, may be contributing to the increased stroke incidence rates detected over the last 10 years.