Lifetime Stroke Risk From Age Twenty Five Onwards Is Approximately One-Fourth and Varies Geographically, According to A New Study Study Determines Lifetime Risk of Stroke at Regional, National, and Global Level: 1990 and 2016

A study conducted by the GBD 2016 Lifetime Risk of Stroke Collaborators demonstrated that the global lifetime risk of stroke from the age of 25 years onward was approximately 25% among both men and women. Moreover, there was geographic variation in the lifetime risk of stroke, with the highest risks in East Asia, Central Europe, and Eastern Europe. The results were published in the New England Journal of Medicine.

The investigators explained the importance of their study, stating that stroke accounts for almost 5% of all disability-adjusted life-years and 10% of all deaths worldwide, with the bulk of this burden (>75% of deaths from stroke and >80% of disability-adjusted life-years) occurring in low-income and middle-income countries.  According to several surveys, the global burden of stroke has been increasing, and the prevention of stroke may require an improved understanding of the risks among younger individuals. Stroke prevention strategies in low-income and middle-income countries may differ from those adopted in high-income countries owing to differences in access to health care, health technologies, and relative rates of risk factors for stroke. Since the lifetime risk of stroke had been calculated in a limited number of selected populations, the investigators, led by Dr. Valery L. Feigin, Director and Professor of the National Institute for Stroke and Applied Neurosciences, sought to estimate the lifetime risk of stroke at the regional, country, and global level using data from a comprehensive study of the prevalence of major diseases.

The Global Burden of Disease (GBD) Study 2016 estimates of stroke incidence and the competing risks of death from any cause other than stroke were used to calculate the cumulative lifetime risks of first stroke, ischemic stroke, or hemorrhagic stroke among adults 25 years of age or older. Estimates of the lifetime risks in the years 1990 and 2016 were compared. Countries were categorized into quintiles of the sociodemographic index (SDI) used in the GBD Study, and the risks were compared across quintiles. Comparisons were made with the use of point estimates and uncertainty intervals representing the 2.5th and 97.5th percentiles around the estimate. The study reported that the estimated global lifetime risk of stroke from the age of 25 years onward was 24.9% (95% uncertainty interval, 23.5 to 26.2); the risk among men being 24.7% (95% uncertainty interval, 23.3 to 26.0), and the risk among women being 25.1% (95% uncertainty interval, 23.7 to 26.5). In addition to this, the risk of ischemic stroke was 18.3%, and the risk of hemorrhagic stroke was 8.2%. In high-SDI, high-middle–SDI, and low- SDI countries, the estimated lifetime risk of stroke was 23.5%, 31.1% (highest risk), and 13.2% (lowest risk), respectively; the 95% uncertainty intervals did not overlap between these categories. The highest estimated lifetime risks of stroke according to GBD region were in East Asia (38.8%), Central Europe (31.7%), and Eastern Europe (31.6%), and the lowest risk was in eastern sub-Saharan Africa (11.8%). The mean global lifetime risk of stroke increased from 22.8% in 1990 to 24.9% in 2016, a relative increase of 8.9% (95% uncertainty interval, 6.2 to 11.5); the competing risk of death from any cause other than stroke was considered in this calculation.

Therefore, this study provided global, regional, and country-specific estimates of the lifetime risk of stroke according to sex and age, although the precision of the estimates was limited by insufficient data in some countries. The global lifetime risk of stroke was approximately 25% starting at the age of 25 years among both men and women, and there was a large geographic variation, with a particularly high lifetime risk of stroke in East Asia, Central Europe, and Eastern Europe. Speaking of the strength of the study, Dr. Valery L. Feigin noted, “The main strength of our study was the systematic use of data and methods that allow for comparable estimates of lifetime risk of stroke among different locations and between different years. We provide estimates of lifetime risk of stroke only among persons 25 years of age or older in contrast to other studies that estimated lifetime risk of stroke among persons 45 years of age or older. Furthermore, the estimates of lifetime risk of stroke that we provide account for competing for risk of death from any cause other than stroke and represent whole populations, possibly making the results generalizable.” However, the investigators acknowledged certain limitations such as a lack of sufficient epidemiologic data on stroke incidence and case fatality for most countries in the world. In these countries, estimates were dependent on geospatial statistical models that incorporated data from neighboring countries and data on country-level risk exposure. The ability to differentiate stroke from other acute neurologic events and to differentiate ischemic from hemorrhagic stroke was impeded by the nature of health system in each country, differences in clinical practice or availability of health care, the technology available to diagnose strokes, and the customary manner of coding disease entities in each country.