Epilepsy affects more than 50 million people worldwide, and while anyone can develop it, certain groups face significantly higher risk. The two biggest peaks in onset occur at opposite ends of life: during infancy and after age 65. Between those peaks, a range of factors, from genetics to brain injuries to infections, can tip the balance.
Age Is the Strongest Risk Factor
Epilepsy is most likely to begin in the first year of life, when the incidence rate reaches 149 per 100,000 person-years. That’s several times higher than the rate during childhood or early adulthood. Babies’ brains are still developing rapidly, making them more vulnerable to seizure activity triggered by genetic conditions, birth complications, or metabolic problems.
The second major peak comes in older adults, typically after age 65. At that stage, the causes shift: stroke, Alzheimer’s disease, brain tumors, and other age-related conditions become the primary drivers. Because populations are aging globally, late-onset epilepsy is becoming an increasingly common diagnosis.
Family History and Genetics
If a parent, sibling, or child has epilepsy, your risk of developing it by age 40 is roughly 4.7%, compared to about 1.3% in the general population. That’s a 3.3-fold increase. The risk is remarkably consistent across relationship types: about 4.5% for parents, 4.8% for siblings, and 3.9% for offspring of someone with epilepsy, based on a population study spanning decades in Olmsted County, Minnesota.
This doesn’t mean epilepsy is always inherited in a straightforward way. Most genetic epilepsies involve multiple genes interacting with each other and with environmental triggers, rather than a single gene passed down. Some rare epilepsy syndromes do follow clear inheritance patterns, but for most people with a family history, the increased risk is real but modest.
Traumatic Brain Injury
A blow to the head can set the stage for epilepsy months or even years later. The risk depends heavily on how severe the injury is. A large Norwegian study found that within five years of a severe traumatic brain injury, about 13% of patients developed epilepsy. Their risk was 25 times higher than people who hadn’t experienced head trauma at all. Moderate injuries carried about 12 times the risk, and even mild traumatic brain injuries raised the risk nearly fourfold.
Post-traumatic epilepsy can appear quickly or slowly. Some people have their first seizure within weeks of the injury, while others don’t develop seizures for years. The brain’s response to injury involves inflammation, scarring, and changes in how nerve cells communicate, all of which can gradually create the conditions for seizures to take hold.
Stroke and Vascular Conditions
Stroke is the leading cause of epilepsy in older adults. Roughly 5% to 10% of stroke survivors experience seizures within the first two weeks, and an additional 3% to 5% develop late-onset seizures or ongoing epilepsy afterward. Depending on the type and location of the stroke, estimates of post-stroke epilepsy range from 3% to 30%.
Hemorrhagic strokes (caused by bleeding in the brain) carry a higher epilepsy risk than ischemic strokes (caused by blood clots), likely because blood in brain tissue is particularly irritating to nerve cells. Strokes that affect the brain’s cortex, the outer layer involved in higher functions, are also more likely to trigger seizures than those deeper in the brain.
Alzheimer’s Disease and Dementia
People with Alzheimer’s disease are about 2.8 times more likely to develop epilepsy than people without it, according to a 10-year nationwide cohort study. This held true even after adjusting for age, sex, and income. The connection likely runs in both directions: the same abnormal protein buildup that damages memory circuits may also make brain cells more excitable, lowering the threshold for seizures. Epilepsy in people with Alzheimer’s can be tricky to recognize because seizures sometimes look like worsening confusion rather than the convulsions most people picture.
Brain Infections
Infections that inflame the brain carry a significant and long-lasting epilepsy risk. Viral encephalitis is the most concerning: people who had seizures during their initial illness face a 22% chance of developing epilepsy over the following 20 years. Even without early seizures, the 20-year risk after viral encephalitis is about 10%.
Bacterial meningitis also raises risk, particularly when seizures occur during the acute infection (13% over 20 years). Without early seizures, the risk after bacterial meningitis drops to around 2.4%. Milder infections like aseptic (viral) meningitis don’t appear to increase epilepsy risk beyond the general population rate.
Parasitic Infections in Endemic Regions
In many low- and middle-income countries across Africa, Asia, and Latin America, a parasitic infection called neurocysticercosis is the single most common preventable cause of epilepsy. It’s caused by the larval stage of a pork tapeworm that can migrate to the brain, where it forms cysts and triggers seizures. The World Health Organization estimates this parasite accounts for 30% of epilepsy cases in endemic areas, and in some high-risk communities, that figure reaches 70%.
The parasite thrives where pigs roam freely, sanitation is poor, and meat inspection is limited. Prevention strategies include treating infected people and pigs, vaccinating pigs, improving sanitation to end open defecation, and educating communities about food safety. These are among the most impactful interventions available for reducing epilepsy rates globally.
Birth Complications and Prematurity
Babies born prematurely or at low birth weight experience neonatal seizures at dramatically higher rates: 10 to 30 per 1,000 live births, compared to about 1 to 3 per 1,000 in full-term infants. Oxygen deprivation during or around delivery (perinatal asphyxia) is one of the most common triggers, along with bleeding in the brain, stroke, infections, and metabolic imbalances. Not all neonatal seizures lead to epilepsy, but they are a significant risk marker, especially when caused by structural brain injury.
Developmental Conditions
Epilepsy overlaps heavily with certain developmental conditions. About 30% of children with autism also have epilepsy, and the relationship goes both ways: roughly 30% of children with epilepsy are on the autism spectrum. The overlap suggests shared underlying differences in how brain circuits develop and regulate their activity. Seizures in children with autism tend to peak during two windows, early childhood and adolescence, which mirrors the general pattern of epilepsy onset in young people.
Other developmental conditions, including intellectual disability and certain genetic syndromes, also carry elevated epilepsy risk. The more significant the underlying brain difference, the higher the likelihood of seizures.
Where You Live Matters
Nearly 80% of people with epilepsy live in low- and middle-income countries. This isn’t just because of parasitic infections. Limited access to obstetric care increases the rate of birth injuries. Fewer emergency services mean head injuries go untreated. Infections that would be caught early in wealthier settings can progress to brain involvement. And once epilepsy develops, the treatment gap is enormous: in some regions, more than 75% of people with epilepsy receive no treatment at all, which means preventable causes go unaddressed and the condition’s burden compounds over time.