An Overview of Sudden Unexpected Death in Epilepsy (SUDEP)

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People with epilepsy have a small but statistically significant risk of sudden death that occurs unexpectedly, and for unclear causes. This tragic event is called sudden, unexpected death in epilepsy, or SUDEP. 

The incidence of SUDEP has been difficult to quantify, but experts have estimated that it accounts for between 2% and 18% of all deaths in people with epilepsy. In children with epilepsy who die, this proportion is thought to be even higher.

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When Is Sudden Death Classified as SUDEP?

Not all sudden deaths in people with epilepsy are classified as SUDEP, only those for which no definitive explanation is found after a thorough investigation. 

SUDEP is defined as a sudden, unexpected death that is not associated with trauma, drowning, or status epilepticus (a prolonged seizure), and a subsequent autopsy shows no structural cause of death (such as a heart attack), and no evidence of a drug overdose or other toxic exposure. 

What Is the Actual Incidence of SUDEP?

Using this definition, the incidence of SUDEP has been estimated to be 0.58 deaths per 1000 person-years in people with epilepsy . In other words, given 2000 people with epilepsy, after one year odds are that roughly one of them would experience SUDEP.

This average estimated risk may not be accurate for an individual with epilepsy, however, because not all people with epilepsy are equally at risk for SUDEP. People who have generalized tonic-clonic seizures are about 10 times more likely to experience SUDEP than people with other forms of epilepsy, and their risk is especially high if their seizures are poorly controlled.


No single cause of SUDEP has been identified. It is currently believed that SUDEP may be produced by one or more of several bodily systems that may become dysfunctional when seizures occur.

There appear to be several cardiac contributors to SUDEP. Seizures have been noted to trigger profound and potentially dangerous bradycardia (slowing of the heart rate). Seizures can also cause a prolongation of the QT interval on the electrocardiogram, and people with long QT syndrome (which often goes undiagnosed) may have fatal ventricular tachycardia as a result. Similarly, the profound release of adrenaline that often occurs during seizures can also trigger ventricular tachycardia in some people.

Respiratory failure is also thought to be a contributor to SUDEP. A seizure may cause a centrally-mediated (that is, originating in the brain) cessation of all breathing for prolonged periods of time, leading to a profound drop in blood oxygen levels and a profound increase in blood carbon dioxide levels. In addition, seizures may produce laryngospasm (closing off of the larynx), making breathing impossible. Seizures may also produce a neurogenic form of pulmonary edema, causing the lungs to fill with fluid.

Seizures may also cause an overall depression of brain function that is severe enough to cause a generalized collapse of the cardiac and respiratory systems, in which both breathing and cardiac activity may stop altogether.

In summary, while it is true that no specific, single “cause” of SUDEP has been identified, all of the above factors are thought to contribute to SUDEP. It is all but certain that in many people SUDEP may be caused by one or more of these mechanisms.

The important thing to note is that all of these postulated mechanisms are associated with active seizure activity. Indeed, while experts have not agreed on a specific cause of SUDEP, most do agree the seizures themselves are likely to trigger one or more of the pathological mechanisms that ultimately cause these sudden deaths.

Risk Factors

In light of these causative mechanisms, it should not be a surprise that the major risk factor for SUDEP is incompletely controlled seizures, especially in people with generalized tonic-clonic seizures.

In fact, people with epilepsy who have more than two generalized seizures per year are 15 times more likely to experience SUDEP than people with fewer than three seizures a year.

Additional risk factors for SUDEP include a genetic predisposition to long-QT syndrome, age under 45 years, alcoholism, and the use of psychotropic drugs. 

Especially in older people with epilepsy, the presence of structural heart disease (such as a prior heart attack, or heart failure) may make them more prone to seizure-induced cardiac arrhythmias that could produce SUDEP.


The most important preventive measure that can be made to prevent SUDEP is to control seizures to the fullest extent possible. If you are on anti-seizure medication and still have more than very rare seizures, every step should be taken to further optimize your therapy and eliminate your seizures altogether if at all possible.

If your seizures persist despite several attempts to control them with medication, you should strongly consider asking for a referral to an epilepsy care center for a comprehensive evaluation. There, you can be considered for drug options that are not commonly used, as well as non-pharmacologic therapy such as epilepsy surgery, vagus nerve stimulation, or a ketogenic diet

Every attempt should be made to eliminate generalized tonic-clonic seizures, not only to help prevent SUDEP, but also to prevent other modes of death which can occur in people with epilepsy, including drowning and death from accidents.

Because many deaths from SUDEP occur during sleep and are unwitnessed, some experts recommend nocturnal monitoring for people with imperfectly controlled generalized seizures. If a seizure is detected at night, steps can be taken (for instance), to stimulate the victim to breathe once the seizure has ended, and thus to prevent respiratory arrest. 

Nocturnal monitoring may include having a loved one sleep in the same room and make periodic checks, or to use monitoring technology to detect seizure activity, noise, or decreased respiration. At least one study concluded that nocturnal monitoring can decrease the risk of SUDEP in people with incompletely controlled epilepsy.

In people with epilepsy, ECGs should be reviewed periodically to look for signs of QT interval prolongation. If the QT interval is prolonged, adjustments may need to be made in medications. If the risk of arrhythmias caused by long-QT syndrome appears high enough, other preventive measures may need to be taken, possibly including beta blockers or an implantable defibrillator.

Finally, it is important for anyone with a seizure disorder to take their anti-seizure medication exactly as prescribed and to avoid excess alcohol, and psychotropic drugs.

A Word From Verywell

If you have epilepsy, it is important that you take the steps that can help to prevent SUDEP. While SUDEP is uncommon, over a lifetime the cumulative risk can become substantial. 

The most important step is to eliminate your seizures, if that is at all possible. If you and your doctor are not completely successful in this regard, you should consider going to a comprehensive epilepsy center to see what more can be done. It is entirely possible that seizures can be eliminated with some combination of medication, surgery and diet. Achieving this outcome will not only reduce your risk of SUDEP, but it will also reduce your risk of injury, and other causes of death associated with seizures. 

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