The global lifetime risk of stroke from the age of 25 years onward is estimated to have increased from 22.8% in 1990 to 24.9% in 2016, with the change in the risk of ischemic stroke exceeding that of hemorrhagic stroke. This increase is the result of unchanged or increasing stroke incidence in many middle-SDI countries and declines in the competing risks of death from any cause other than stroke. The estimated global lifetime risk of stroke has declined with increasing age, in part owing to age-related competing risks of other diseases. In low-SDI countries (generally, countries with the youngest populations, such as those in sub-Saharan Africa), the estimated lower lifetime risk of stroke is the result of a high competing risk of death from any cause other than stroke at both younger and older ages and does not necessarily represent a lower incidence of stroke or more effective prevention and treatment strategies.2,17

Many of the national estimated lifetime risks of stroke reported here are similar to or higher than those observed in specific populations in the same country in studies other than the GBD Study, such as in the Framingham Heart Study cohort in the United States (lifetime risk of stroke of 21.1% among women and 16.9% among men),18 in a Japanese cohort (lifetime risk of stroke of 18.9% among men and 20.2% among women),8 and in a Chinese cohort (lifetime risk of stroke of 18.0% among men and 14.7% among women).7 A study of stroke in the Netherlands showed that the risk among men was 22.8%, which is similar to our estimate for that country, but the risk among women (29.8%) was lower than our estimate.9 We estimated ischemic stroke to be more frequent than hemorrhagic stroke — a finding that is similar to those of other population-based studies.6,8,12,13,19

Regional variation in lifetime cardiovascular risk across subpopulations has been shown previously in the Cardiovascular Lifetime Risk Pooling Project and is compatible with our finding of large geographic variation in lifetime risk of stroke.10 Our findings that the lifetime risk of stroke is similar among men and among women are in accord with some other observations; however, there have been studies8-10,19 in which the risk was greater among women than among men, and the reasons for these differences between studies are unclear. In the comparative risk assessment performed in the GBD Study,4,20 elevated blood pressure was estimated as the leading attributable risk factor for stroke across all SDI quintiles, with greater attribution to air pollution and low intake of fruit in low-SDI countries and high body-mass index and high fasting plasma glucose levels in high-SDI countries.

The use of estimates of lifetime risk of disease is a new metric for the GBD Study, which has previously published summary measures of health including years of life lost prematurely, years lived with disability,2,3,20 and stroke burden associated with various risk factors.4 Knowledge of lifetime risk may be useful for stroke prevention and public education. High estimates of lifetime risk of stroke suggest that there is possible value of measures for the primary prevention of stroke throughout a person’s lifespan and suggest that strategies to reduce cardiovascular risk remain relevant for both younger and older adults.

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.6,8-10 Furthermore, the estimates of lifetime risk of stroke that we provide account for competing risk of death from any cause other than stroke and represent whole populations, possibly making the results generalizable.

The epidemiologic approaches used in our study have limitations. The accuracy of the estimates of lifetime risk of stroke was limited by the accuracy and availability of epidemiologic data from the countries studied. There was 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. We did not differentiate between subarachnoid hemorrhagic and intracerebral hemorrhagic stroke; these were combined in the estimate of hemorrhagic stroke. There is significant variation in stroke burden within large countries, and our results represent only the mean national risk. Finally, we analyzed only the lifetime risk of first-ever stroke and not recurrent stroke.

In conclusion, our 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 is limited by insufficient data in some countries. The global lifetime risk of stroke is approximately 25% starting at the age of 25 years among both men and women, and there is large geographic variation, with a particularly high lifetime risk of stroke in East Asia, Central Europe, and Eastern Europe.