Proportion of older people in the community as a predictor of increasing stroke incidence

Objectives: To compare stroke incidence rates among comparable registries and to make correlations with aging of the resident populations.

Methods: This correlation study included all comparable stroke registries maintained in industrialized countries (Italy, France, United Kingdom, Denmark, Norway, United States, and Australia). Eleven community-based stroke registries with similar high proportions of radiologically confirmed diagnoses based on standard definitions were identified. Incidence rates of first-ever stroke from the prospective L'Aquila registry and from the other registries were compared after age and sex standardization to the 1996 European population. The rates were then correlated with the proportion of individuals aged 65 and over in the corresponding resident populations by means of the Poisson regression analysis.

Results: In the L'Aquila registry, the crude annual incidence of first-ever stroke was 281/100,000 (95% confidence interval 271-293) based on 2,515 patients included during a 3-year period. The rate standardized to the European population was 249/100,000. Standardized incidence ratios indicated a significant excess of first-ever strokes in the L'Aquila registry up to 51% with respect to most of the compared studies. A significant correlation was also found between crude (p < 0.0001) and standardized (p = 0.0012) stroke incidence rates and proportions of individuals aged 65 and over in the different populations.

Conclusions: The L'Aquila experience suggests that any further aging of a population will increase the stroke occurrence for both the reasons of a direct and predictable effect of the growing proportion of elderly individuals within that population and a disproportionately increased stroke risk in the older age groups.