Seizures can cause death through several distinct pathways: by shutting down breathing, disrupting heart rhythm, or creating dangerous situations like drowning. The most common cause of seizure-related death is a condition called SUDEP (Sudden Unexpected Death in Epilepsy), which kills roughly 1.2 out of every 1,000 people with epilepsy each year. Understanding how these deaths happen also reveals what can be done to reduce the risk.
SUDEP: The Leading Cause of Seizure Death
SUDEP refers to the sudden, unexplained death of someone with epilepsy when no other cause, like trauma or drowning, can be found. It almost always follows a generalized tonic-clonic seizure, the type involving full-body convulsions and loss of consciousness. The death typically occurs during or shortly after the seizure, often during sleep, and the person is usually found in bed.
SUDEP isn’t caused by one single failure. It results from a cascade where the brain loses control of breathing and heart function simultaneously. After a major seizure, the brain enters a period of electrical suppression, essentially going quiet. In monitored cases where SUDEP occurred, every patient showed this suppression pattern. When it lasts longer than 50 seconds, the risk of death rises significantly. During this window, the brainstem regions that control automatic breathing and heart rate are impaired, and if both systems fail at the same time, the person dies.
How Seizures Stop Breathing
Breathing failure is the most critical pathway. Seizures disrupt the brainstem’s breathing centers in two ways. The first is central apnea, where the brain simply stops sending the signal to breathe. This affects nearly half of people with focal epilepsy during or after seizures. Most episodes resolve on their own, but severe ones can be fatal. The amygdala, a brain structure involved in emotion and autonomic function, plays a key role here. When seizure activity spreads to the amygdala, it can trigger respiratory arrest directly.
The second mechanism is obstructive. Seizures can cause laryngospasm, an involuntary clamping shut of the vocal cords. The person’s body tries to inhale against a closed airway, and oxygen levels plummet. In monitored cases, severe drops in blood oxygen (below 75% saturation, where normal is 95% or higher) were strongly linked to longer periods of brain suppression afterward, creating a vicious cycle: the seizure causes oxygen deprivation, which worsens brainstem shutdown, which further impairs breathing.
How Seizures Disrupt the Heart
Major seizures flood the nervous system with competing signals. The brain regions that regulate heart rate and blood pressure, particularly the insular cortex and brainstem, get caught in the electrical storm. This creates a tug-of-war between the two branches of the autonomic nervous system. Overactivation of one branch drives the heart dangerously fast. Overactivation of the other slows it to a crawl or stops it entirely.
Most seizure-related heart pauses last between 3 and 20 seconds and resolve without harm. But longer pauses have been observed, and when combined with the breathing failure described above, even brief cardiac disruption can become fatal. In studied SUDEP cases, the final event was typically cardiorespiratory arrest, where both breathing and heart function collapsed in the minutes following the seizure rather than during the seizure itself. This postictal window, the recovery period after a seizure, is when the greatest danger lies.
Status Epilepticus
Status epilepticus is a seizure that doesn’t stop on its own or a series of seizures without recovery between them. It’s a medical emergency. The 30-day mortality rate is about 8.5% overall, and roughly 10% in adults. The longer a seizure continues, the harder it becomes to stop and the more damage it inflicts. Prolonged seizure activity causes brain cells to die from overstimulation, body temperature to spike, muscles to break down (releasing proteins that can damage the kidneys), and the same breathing and cardiac failures described above to become increasingly likely.
Aspiration and Drowning
During a convulsive seizure, the normal reflexes that protect the airway are impaired. Saliva, vomit, or other fluids can be inhaled into the lungs. This is called aspiration, and it can lead to pneumonia that develops in the hours or days after the seizure. Research on over 1,600 adults found that aspiration pneumonia occurred in roughly 1 out of every 350 to 500 generalized tonic-clonic seizures. The risk is highest during the late phase of the seizure, when increased oral secretions and impaired swallowing combine with the person’s altered consciousness.
Drowning is another major risk. People with epilepsy are 15 to 19 times more likely to drown than the general population. A seizure in a bathtub, pool, or open water leaves the person unable to keep their head above the surface. Even shallow water is dangerous when consciousness is lost. This is why most epilepsy safety guidance strongly emphasizes never swimming alone and choosing showers over baths.
Falls and Other Injuries
Seizures that cause sudden loss of consciousness can lead to fatal injuries from falls. Hitting the head on a hard surface, falling down stairs, or collapsing near traffic or heavy machinery are all scenarios where the seizure itself may not be fatal, but the circumstances around it are. These deaths are classified differently from SUDEP because the cause is identifiable trauma, but they remain a significant source of seizure-related mortality.
Who Is Most at Risk
The single biggest risk factor for SUDEP is the frequency of generalized tonic-clonic seizures. Having just 1 to 3 of these seizures in the previous year raises the risk 22-fold compared to someone with no recent convulsive seizures. Having 4 to 10 raises it 32-fold. Interestingly, the risk doesn’t continue climbing above 10 seizures per year, suggesting a plateau effect.
Other factors that increase risk include seizures that occur during sleep, poor adherence to medication, and living alone. Certain epilepsy syndromes carry especially high risk. In Dravet syndrome, a severe form of childhood epilepsy, SUDEP is the leading cause of death.
What Reduces the Risk
The most effective way to reduce seizure-related death is to reduce seizure frequency, particularly convulsive seizures. Taking medication consistently is the foundation. For people whose seizures don’t respond to medication, surgical options or other treatments may help.
Nighttime supervision appears protective. Having a roommate or using a listening device is associated with lower SUDEP risk, likely because someone nearby can reposition the person, clear their airway, or begin resuscitation during the vulnerable postictal period when cardiopulmonary dysfunction may still be reversible. Seizure-detection devices that send alerts to caregivers are increasingly available, though no study has yet proven they reduce SUDEP rates directly. One limitation is response time: in a reported case, a detection device correctly identified a seizure and alerted the patient’s parents, but they were 15 minutes away and arrived too late.
Sleeping on your back or side rather than face-down may also matter, since prone positioning can obstruct breathing during the postictal period when normal protective reflexes are suppressed. Simple environmental precautions, like avoiding solo baths and using shower seats, address the drowning risk that remains elevated throughout a person’s life with epilepsy.