FRIDAY, April 8 (HealthDay News) -- People with epileptic seizures are much more likely than others to be diagnosed with a brain tumor, a new study indicates.

The findings suggest that epileptic seizures may indicate the presence of a very early-stage tumor or a tumor that hasn't been detected on brain scans, the researchers noted.

They looked at data on hospital admissions between 1963 and 2005 and subsequent diagnoses of, or deaths from, brain tumors among those patients. The analysis revealed that people who had a first-ever hospital admission for epileptic seizure were nearly 20 times more likely to develop a brain tumor than people admitted to the hospital for other reasons.

Even when the researchers factored in the possibility that brain tumors might have been missed or not recorded in the first year after admission for epilepsy, the risk was still 7.5 to nine times higher for patients with epileptic seizures.

The study also found that people with epilepsy were more than 25 times as likely to develop a cancerous brain tumor and more than 10 times as likely to develop a benign tumor than other patients.

The greatest risk was in epilepsy patients aged 15-44, who were 24 to 38 times more likely to develop a brain tumor than people of the same age without epilepsy.

The risk of brain tumor persisted for some years after an initial epilepsy-related hospitalization -- up to a more than sixfold greater risk for as long as 14 years.

Brain tumors are rare, even among those with epilepsy, the researchers noted. The overall risk of a brain tumor in 15-to-44-year-olds, for example, was about 1 percent to 2 percent.

"Our study suggests that tumor as an underlying cause for epilepsy may not become apparent for several years after onset, and indicates a need for ongoing vigilance," the researchers wrote.

The study appears online in the Journal of Neurology Neurosurgery and Psychiatry.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about epilepsy.