LOS ANGELES, April 30 (Xinhua) -- Sleep apnea and low oxygen levels while sleeping are associated with epilepsy that first occurs after 60 years of age, known as late-onset epilepsy, according to a new study funded by the U.S. National Institutes of Health (NIH).

The link was independent of other known risk factors for late-onset epilepsy and sleep apnea including hypertension and stroke, NIH said on Tuesday.

The findings may help to better understand the relationship between sleep disorders and late-onset epilepsy, as well as identify potential targets for treatment, according to NIH.

Researchers at Johns Hopkins University identified cases of late-onset epilepsy using Medicare claims and analyzed sleep data from more than 1,300 participants in a study of sleep-disordered breathing and cardiovascular disease.

They found that people whose oxygen saturation fell below 80 percent during sleep, a condition known as nocturnal hypoxia, were three times more likely to develop late-onset epilepsy compared to those who did not have similarly low oxygen levels.

In addition, participants with self-reported sleep apnea in later life were twice as likely to develop late-onset epilepsy as those without the sleep disorder, according to the study, published in Sleep.

"There's increasing evidence that late-onset epilepsy may be indicative of underlying vascular disease, or neurodegenerative disease, even potentially as a preclinical marker of neurodegenerative disease," said Rebecca Gottesman, chief of the Stroke Branch at the NIH's National Institute of Neurological Disorders and Stroke, and an author on the study.

"Compared to other age groups, older adults have the highest incidence of new cases of epilepsy - up to half of which have no clear cause. Sleep apnea is common among people with epilepsy, but the association is not well understood," said Gottesman.