Trends in stroke incidence. The Copenhagen City Heart Study

BACKGROUND AND PURPOSE: Stroke incidence has increased in some countries and decreased in others. After 20 years of intensive antihypertensive treatment the latter could be expected, and we have evaluated the sex-specific temporal trends in stroke incidence using 17 years of follow-up in the Copenhagen City Heart Study.

SUBJECTS AND METHODS: Our cohort comprised 19,698 subjects living in Copenhagen, Denmark. They were invited for health examinations in the following time periods: 1976 through 1978, 1981 through 1983, and 1992 through 1994. Trends are presented for all persons who attended at least one of the two first examinations as well as the total cohort including nonresponders. Subjects between 45 and 84 years of age were followed from March 1, 1976 until March 1, 1993. Changes in age-specific stroke incidence were calculated by means of Poisson regression analysis.

RESULTS: For subjects aged 45 to 64 years, no significant trends were observed, with an annual incidence rate ratio of 1.00 (95% confidence interval [CI], 0.97 to 1.03) and 1.04 (95% CI, 0.99 to 1.08) for men and women, respectively. In subjects aged 65 to 84 years a significant decrease in stroke incidence was found in men, whose annual rate ratio was 0.97 (95% CI, 0.95 to 0.99), but not in women, whose annual rate ratio was 0.98 (95% CI, 0.95 to 1.00). Throughout four observed periods the stroke incidence among men remained significantly higher than that for women.

CONCLUSIONS: During the period from 1976 to 1993 there has been a decline in incidence of stroke in men and women aged 65 to 84 years that was significant only in men, whereas no changes were found for persons aged 45 to 64 years.