WEDNESDAY, Dec. 22 (HealthDay News) -- People with childhood epilepsy who continue to have seizures into adolescence and beyond face a significantly higher risk of death than people who've never had epilepsy, new research suggests.

In a study that followed 245 children for 40 years following their epilepsy diagnosis, researchers found that 24 percent died during that time period. That's a rate of death that's three times as high as would be expected for people without epilepsy who were of a similar age and sex.

"In those people with childhood-onset epilepsy, those who do not outgrow their seizures have a substantially higher mortality rate over many years," said study senior author Dr. Shlomo Shinnar, director of the Comprehensive Epilepsy Management Center at the Children's Hospital of Montefiore in New York City. But, he added, the risk to any individual in any given year is still less than 1 percent.

And the good news from the study is that "once you have seizure remission, mortality rates are similar [to people without epilepsy]," noted Shinnar.

The findings are published in the Dec. 23 issue of the New England Journal of Medicine.

Epilepsy is a disorder of the brain caused by abnormal signaling messages from nerve cell to nerve cell, according to the U.S. National Institute of Neurological Diseases and Stroke. Those abnormal signals can cause strange sensations, muscle spasms, seizures and even a loss of consciousness.

The most serious complication that occurs more often in people with epilepsy is sudden unexplained death. However, little is known about why this is so.

The current study included 245 children living in Finland who were diagnosed with epilepsy in 1964. The children were followed prospectively for 40 years, and in most cases, when a death occurred, an autopsy was performed.

The researchers found that 60 (24 percent) of the study volunteers died during the follow-up period. Forty eight percent of those who died had experienced seizures in the previous five years.

Not all of the deaths were related to epilepsy, but the researchers found that 33 (55 percent) were. Eighteen of the deaths were considered sudden unexplained deaths. Nine people had either a definite or probably seizure before dying, and six accidentally drowned, presumably as a result of a seizure while swimming or bathing alone.

The overall risk of sudden, unexplained death was 7 percent over 40 years. In an analysis that only included people who weren't in long-term epilepsy remission and who weren't receiving medication, the overall risk of sudden, unexplained death was 12 percent, according to the study.

"Epilepsy is a serious disorder, which has increasingly recognized comorbidities, including -- if it persists into adulthood -- an increased risk of death," said Shinnar.

Although the researchers don't know why the risk of sudden death is increased in people with epilepsy, Shinnar said it's a good idea to try to maintain full seizure control and to be compliant with your medications.

"People who are doing OK may start skipping their medications or forgetting them," he said, but added, "We really don't know if seizure control could make a difference in the risk of sudden, unexplained death."

Another expert said the risk needs to be put into perspective.

"The risk of sudden, unexplained death is real and it's there, but the numbers are not humongous. There's not a sudden, unexplained death epidemic," said Dr. Inna Vaisleib, a pediatric neurologist and epileptologist at Children's Hospital of Pittsburgh.

She pointed out that the researchers were able to identify some risk factors associated with an increased risk of death, such as the absence of a five-year remission, a history of prolonged seizures (status epilepticus) and epilepsy with symptomatic causes, such as a head trauma or a neurological problem.

Still, Vaislieb said, most parents don't need to be overly concerned. About 70 percent of children outgrow their epilepsy by adolescence, she noted, and kids who stop having seizures don't have an increased risk of death.

More information

Learn more about epilepsy from the Epilepsy Foundation.