A stroke is a medical emergency characterized by a sudden disruption of blood flow to the brain, leading to brain cell damage or death. This interruption can occur either when a blood vessel supplying the brain is blocked by a clot or when a blood vessel within the brain bursts. Strokes represent a significant global health challenge, ranking as a leading cause of disability and mortality worldwide.
Defining Stroke Prevalence and Its Scope
Prevalence, in the context of stroke, refers to the total number of individuals living with the effects of a stroke within a specific population at a given time. This differs from incidence, which measures only new cases occurring over a particular period. Globally, over 101 million people are currently living who have experienced a stroke.
Stroke can be broadly categorized into two main types: ischemic and hemorrhagic. Ischemic strokes, caused by a blockage in a blood vessel, account for about 87% of all strokes. Hemorrhagic strokes, which involve bleeding into or around the brain, make up the remaining proportion, about 13%. While ischemic strokes are more common, hemorrhagic strokes can lead to more severe outcomes, including higher mortality rates.
Demographic Patterns of Stroke
Stroke prevalence shows distinct patterns across different demographic groups, with age being a primary determinant. The risk of stroke increases significantly with advancing age, with incidence doubling for each decade after 55 years of age. Despite this, strokes can occur at any age, including in children.
Gender also plays a role in stroke patterns; men have a higher age-adjusted stroke risk than women, particularly at younger ages. However, women are more likely to die from stroke, even though men account for more than half of all strokes. Racial and ethnic disparities are also evident, with African Americans having almost double the risk of a first stroke compared to White individuals. Hispanic Americans and American Indian/Alaska Natives also face a greater risk of stroke than White people, though less than African Americans.
Risk Factors and Their Contribution to Prevalence
Numerous factors contribute to an individual’s risk of stroke, categorized as either modifiable or non-modifiable. Modifiable risk factors are those that can be changed or managed through lifestyle adjustments or medical interventions, and they account for a significant portion of stroke burden. Non-modifiable factors, such as age, sex, race/ethnicity, and genetics, cannot be altered.
Hypertension, or high blood pressure, is the most significant modifiable risk factor for stroke, demonstrating a direct and continuous relationship with stroke risk. Uncontrolled hypertension can damage blood vessels, leading to blockages or ruptures. Diabetes also increases stroke risk by damaging blood vessels due to high glucose levels, making them more prone to narrowing. High cholesterol contributes to the buildup of fatty deposits, known as atherosclerosis, which can narrow arteries and impede blood flow to the brain. Obesity is linked to increased risks of hypertension and diabetes, both of which are significant stroke contributors.
Behavioral factors like smoking significantly increase stroke risk as nicotine and tar narrow blood vessels and reduce oxygen supply to the brain. Physical inactivity weakens blood flow regulation and insulin control, further elevating risk. An unhealthy diet, particularly one low in fruits and vegetables and high in processed foods, can deprive neurons of antioxidants and contribute to high cholesterol and obesity, indirectly increasing stroke risk. Excessive alcohol consumption can also raise blood pressure and cholesterol levels, contributing to weight gain. Family history and genetic predispositions, while non-modifiable, indicate an increased likelihood of stroke, often due to inherited tendencies toward other risk factors.
Changes in Stroke Prevalence Over Time
Global trends in stroke prevalence show changes over time. From 1990 to 2021, the absolute number of people experiencing new strokes increased by 70%, and stroke survivors rose by 86%. This rise is largely attributed to global population growth and an aging demographic.
Despite the increase in absolute numbers, age-standardized rates of stroke incidence, prevalence, and mortality have shown a downward trend globally since 1990, suggesting improvements in prevention and care. However, this progress has not been uniform across all regions and age groups. Since 2015, there has been a stagnation in the reduction of incidence rates, and even some increases in stroke incidence, death, and prevalence rates in regions like Southeast Asia, East Asia, and Oceania, particularly among individuals younger than 70 years. This indicates the ongoing challenge of stroke and the need for continued efforts in prevention and management worldwide.