Stable Stroke Occurrence Despite Incidence Reduction in an Aging Population

Abstract

Background and Purpose —A stroke register was established at the Glostrup Population Studies in 1982 with the objective to monitor stroke occurrence in the population continuously during a 10-year period and contribute data to the WHO Monitoring Trends and Determinants in Cardiovascular Disease (MONICA) Project. The purpose of the current analysis was to estimate temporal trends in stroke occurrence. Methods —All stroke events in the study population were ascertained and validated according to standardized criteria outlined by the WHO MONICA Project. The study population comprised all subjects ≥25 years of age. Stroke was defined by the clinical presentation. A total of 5262 stroke events in >2 million person-years were analyzed. Age-adjusted rates for first-ever stroke and for all stroke events were calculated and temporal trends estimated by means of Poisson regression. Results —The overall annual stroke attack rate per 100 000 person-years in the age range ≥25 years was 272 in men and 226 in women. Age-adjusted stroke attack rates decreased among men by 3.9% per year and by 4.1% among women. Age-adjusted stroke incidence rates declined by 2.9% in men and by 3.1% in women. The trends were statistically significant in both sexes. However, the proportion of elderly people in the study population increased during the time period of the study. Hence the numbers of stroke victims in the population remained largely unaltered. Conclusions —Decreasing age-adjusted stroke incidence rates point to a reduction of stroke risk during the time period of the study. Cardiovascular prevention, in particular improved hypertension control, is believed to have contributed to the incidence reduction. However, the burden of stroke on the healthcare system did not substantially diminish. The gain likely achieved from reduction of preventable risk factors was almost counterbalanced by population aging.