Stroke occurs when poor blood flow to the brain causes the death of brain cells. This interruption is either caused by a blockage (ischemic stroke) or by bleeding within the brain (hemorrhagic stroke). While traditionally associated with older age, strokes are increasingly observed in younger people, typically defined as those under 45 or 50. The underlying causes in this demographic differ significantly from those seen in the elderly, pointing instead to a complex mix of structural, genetic, and environmental triggers.
Structural Abnormalities in the Vasculature
Physical defects in the blood vessels or the heart are a leading cause of stroke in young adults. One common cause is arterial dissection, which involves a tear in the inner layer (intima) of a neck artery, such as the carotid or vertebral artery. Blood enters this tear, forming a hematoma that can block blood flow or serve as a source for a clot, causing an ischemic stroke. This dissection frequently follows minor trauma, such as sudden neck movement, whiplash, or aggressive coughing.
Another structural cause is Patent Foramen Ovale (PFO), a small opening between the upper chambers of the heart that failed to close after birth. Although present in about 25% of the population, PFO can lead to stroke via paradoxical embolism. A blood clot originating in the venous system (e.g., deep vein thrombosis) can pass directly through the PFO from the right side of the heart to the left, traveling straight to the brain. Arteriovenous Malformations (AVMs) are a different anomaly: a tangled mass of vessels where arteries connect directly to veins without the typical capillary network. This high-pressure connection weakens the vessel walls, making them prone to rupture, which causes hemorrhagic stroke in young people.
Conditions Affecting Blood Clotting
Certain inherited and acquired conditions predispose young people to forming blood clots, creating a hypercoagulable state. Inherited thrombophilias, such as Factor V Leiden mutation, increase the risk of thrombosis. This mutation causes a clotting factor to become resistant to inactivation by Activated Protein C, leading to prolonged clotting action. The Prothrombin Gene Mutation (G20210A) also contributes by causing the body to produce elevated levels of prothrombin, the precursor to the clot-forming enzyme, thrombin.
Acquired conditions also raise the risk for stroke, notably Antiphospholipid Syndrome (APS). APS is an autoimmune disorder where autoantibodies target proteins, leading to platelet activation and endothelial damage. This results in a chronic prothrombotic state that increases the risk of arterial and venous thrombosis, accounting for a percentage of strokes in individuals under 45. Sickle Cell Disease (SCD) is another factor, particularly in children and young adults, where abnormal red blood cells obstruct small vessels (vaso-occlusion). Repeated sickling episodes damage cerebral vessel walls, causing chronic narrowing and inflammation, resulting in both ischemic and hemorrhagic stroke.
Autoimmune and Systemic Inflammatory Disorders
Chronic systemic inflammation can directly damage blood vessel walls, leading to increased stroke risk in young adults. Systemic Lupus Erythematosus (SLE) is one such autoimmune condition, where chronic inflammation accelerates atherosclerosis and causes small vessel disease. The stroke risk in SLE patients is often a result of co-existing Antiphospholipid Syndrome, involving both inflammatory and thrombotic mechanisms.
Vasculitis encompasses disorders where blood vessel walls become inflamed, narrowed, or blocked. Moyamoya disease is a progressive condition characterized by the narrowing of the internal carotid arteries, prompting the growth of a fragile network of collateral vessels. These thin vessels can rupture (hemorrhagic stroke) or fail to supply enough blood (ischemic stroke). Takayasu Arteritis is another form of vasculitis that affects the aorta and its major branches, causing severe stenosis or occlusion of the vessels leading to the brain, resulting in ischemic stroke.
The link between Migraine with Aura and ischemic stroke exists, particularly in younger women. Although the absolute risk is low, the presence of aura is associated with increased stroke risk, thought to involve temporary cerebral vasospasm or a transient prothrombotic state during the migraine. This risk is amplified when migraine with aura co-occurs with other vascular risk factors.
Lifestyle Factors and Acute Triggers
Certain lifestyle choices and acute exposures can act as direct triggers for stroke, often by exacerbating an underlying vulnerability. Illicit drug use, particularly of stimulants like cocaine and methamphetamines, causes both ischemic and hemorrhagic stroke. These drugs cause a sudden surge in blood pressure and cerebral vasospasm (narrowing of the brain’s blood vessels), which can rupture a vessel or induce an ischemic event.
Hormonal contraceptives, especially high-dose estrogen formulations, increase clotting factors while reducing natural anticoagulants, promoting a prothrombotic state. While the absolute risk is low for healthy women, it is amplified when combined with other risk factors such as smoking or an inherited thrombophilia. Poorly controlled hypertension and diabetes, though traditionally associated with older adults, accelerate vascular damage in young people. Sustained high blood pressure mechanically injures the vessel lining, and chronic hyperglycemia promotes inflammation and small vessel disease, hastening stroke development.