A stroke, often described as a “brain attack,” occurs when the blood supply to a part of the brain is interrupted by a blockage or a ruptured blood vessel. This interruption prevents brain tissue from receiving oxygen and nutrients, leading to cell death within minutes. Strokes are a leading cause of long-term disability and the fifth leading cause of death in the United States. The frequency of a stroke varies dramatically based on the type, geographic location, and a person’s unique combination of risk factors.
Overall Prevalence and Incidence
Understanding how common a stroke is requires distinguishing between incidence (new cases diagnosed within a specific period) and prevalence (the total number of people living with the condition). In the United States, someone has a stroke every 40 seconds, illustrating a high rate of incidence.
More than 795,000 people in the country experience a stroke each year, a figure that includes both first-time and recurrent events. Approximately 610,000 of this annual total are first or new strokes. The remaining 185,000, or nearly one in four, occur in people who have previously had one. The overall lifetime risk of experiencing a stroke from middle age onward is estimated to be around one in six or more.
The lifetime risk is slightly higher for women, approximating one in five, compared to men, whose risk approximates one in six. This difference is partly due to women’s generally longer life expectancy. Globally, the lifetime risk is estimated to be about one in four adults from age 25 onward.
Variation by Stroke Type
Strokes are categorized primarily into two main types: ischemic and hemorrhagic. Ischemic strokes are the most frequent type, accounting for about 87% of all cases, and occur when a blood vessel supplying the brain becomes blocked, typically by a blood clot. A third category, transient ischemic attack (TIA), serves as a warning event.
Conversely, hemorrhagic strokes are far less common, making up only about 13% of all strokes. This type is caused by a weakened blood vessel rupturing and bleeding into the surrounding brain tissue. While less frequent, hemorrhagic strokes often carry a higher immediate risk of death compared to ischemic events.
A transient ischemic attack (TIA), sometimes called a “mini-stroke,” is caused by a temporary clot that briefly interrupts blood flow. TIA symptoms typically disappear within an hour, and always within 24 hours. Although a TIA does not cause permanent damage, it is an important warning sign of an impending, more severe event and requires immediate medical attention.
Demographic and Lifestyle Risk Factors
National statistics only provide a general baseline, as a person’s individual likelihood of having a stroke is highly personalized by their demographic and lifestyle factors. Age is the most robust non-modifiable factor, with the risk of an incident stroke effectively doubling every 10 years after the age of 55. While nearly three-quarters of all strokes occur in people aged 65 and older, about 10% to 15% of strokes occur in people under the age of 50, a proportion that is trending upward.
Race and ethnicity introduce further disparity, profoundly affecting the risk profile. The risk of having a first stroke is nearly twice as high for non-Hispanic Black adults as it is for White adults. This group also experiences the highest rate of stroke-related death, a disparity often linked to differences in the prevalence and management of conditions like hypertension.
Controllable health factors have the largest potential to modify an individual’s risk of stroke. High blood pressure is a significant determinant, and maintaining normal blood pressure can reduce the lifetime risk of stroke by approximately half compared to those with high blood pressure. Similarly, a person who smokes faces a risk of stroke that is three to four times higher than a non-smoker.
The impact of managing these factors can be quantified. For example, quitting smoking after an ischemic stroke or TIA is associated with a 34% reduction in the risk of a subsequent stroke, heart attack, or death over a five-year period.
Global and Temporal Trends in Occurrence
The overall occurrence of stroke is changing over time and across different geographic regions. In many high-income countries, the age-standardized rate of stroke incidence has been decreasing by approximately 20% to 30% over the last few decades. This decline is attributed to better public health initiatives and improved medical management of conditions like high blood pressure and high cholesterol.
Despite this progress in developed nations, the overall global burden of stroke is rising. This is due to a paradox where decreasing age-standardized rates are offset by the world’s rapidly aging and growing population. The overall number of stroke cases and deaths worldwide has increased substantially, with a disproportionate number of cases now occurring in low- and middle-income countries.
In the United States, while incidence among people aged 55 and older has decreased, the rate of stroke has increased significantly among adults younger than 55 years old. This shift toward younger stroke patients is linked to the rising prevalence of risk factors such as obesity, diabetes, and hypertension in this younger demographic.