A stroke occurs when blood flow to an area of the brain is interrupted, causing brain cells to die. This interruption is typically caused by a blockage, known as an ischemic stroke, or bleeding, called a hemorrhagic stroke. Ischemic strokes account for about 87% of all cases. While the risk profile changes dramatically across the lifespan, a stroke is not confined to a single age group and can occur at any point, from before birth to advanced age.
Stroke Risk in Advanced Age
Advanced age is recognized as the single strongest non-modifiable risk factor for stroke, with the majority of all strokes—approximately three-quarters—occurring in individuals aged 65 or older. The incidence of stroke effectively doubles with every decade after the age of 55. This heightened risk is largely due to the cumulative effects of long-term wear and tear on the body’s vascular system.
The primary causes in this demographic are linked to chronic cardiovascular conditions that have developed over decades. Atherosclerosis, the hardening and narrowing of arteries due to plaque buildup, restricts blood flow and raises the likelihood of clot formation. Uncontrolled high blood pressure, or hypertension, is the most common underlying cause for both ischemic stroke and hemorrhagic stroke in older adults, damaging blood vessel walls over time.
Atrial fibrillation (A-fib), an irregular heart rhythm, becomes more common with age. This condition allows blood to pool and clot in the heart’s upper chambers. If a clot breaks off, it can travel to the brain and cause an ischemic stroke.
Strokes Affecting Young and Middle-Aged Adults
Approximately 10% to 15% of all strokes occur in adults aged 18 to 50, a proportion that has been increasing in recent years. The causes in this working-age population often involve mechanisms distinct from typical age-related vascular issues. For instance, a tear in the wall of an artery in the neck, known as arterial dissection, accounts for a substantial percentage of strokes in young adults.
Congenital heart issues that may have gone undetected also play a role, such as a patent foramen ovale (PFO), a small opening between the upper heart chambers. A PFO can allow a clot to pass directly to the brain. Autoimmune conditions, like systemic lupus erythematosus, can also raise stroke risk by inducing inflammation and increasing the blood’s tendency to clot.
The rising incidence is also tied to an increase in traditional risk factors, such as obesity, high blood pressure, and type 2 diabetes. Lifestyle factors, including tobacco use, heavy alcohol consumption, and the use of illicit substances, significantly increase the risk of stroke in this younger demographic. For women, specific factors like certain oral contraceptives or complications from pregnancy can also elevate stroke risk.
The Rarity of Pediatric Stroke
Stroke is less common in the pediatric population, which includes infants, children, and adolescents up to age 18, but it remains a serious health event. The causes of stroke in a child are often unique and not related to the typical atherosclerosis seen in older adults. Perinatal stroke, which happens around the time of birth, is a specific concern, often due to issues like low oxygen supply or clotting problems.
In older children, many strokes are linked to underlying genetic or congenital disorders. Sickle cell disease is a condition that can cause blood cells to become sticky and block brain vessels, increasing the stroke risk by up to 200 times. Congenital heart defects, such as complex heart malformations, can also predispose a child to clot-related strokes.
Infections are another distinct cause, as some infectious diseases, like meningitis or varicella (chickenpox), can trigger inflammation in the brain’s blood vessels. Blood clotting disorders, known as prothrombotic states, whether inherited or acquired, are also a common finding in children who experience a stroke.
The Changing Landscape of Stroke Causes Across the Lifespan
The underlying mechanisms of stroke shift dramatically across the spectrum of human age, reflecting different stages of physiological development and health accumulation. In the youngest population, the causes are rooted in genetics, congenital abnormalities, or acute infectious events. This means the stroke risk is less about chronic disease and more about inherent structural or hematological conditions.
As individuals enter young and middle adulthood, the risk profile begins to transition, involving unique, structural issues like arterial dissections or less common cardiac defects. This period also marks the beginning of risk accumulation, with an increasing contribution from traditional lifestyle factors like hypertension and obesity. This convergence of unique and acquired risks defines the stroke landscape in the working-age population.
In advanced age, the risk overwhelmingly becomes a matter of long-term vascular health, driven by the accumulated effects of years of high blood pressure, cholesterol, and the development of degenerative heart conditions like atrial fibrillation. The underlying reason for the brain attack changes from congenital and acute causes in youth to chronic, degenerative vascular disease in later life.