WASHINGTON -- Age at menarche was significantly associated with seizure onset age in epileptic women, according to a study presented at the American Epilepsy Society annual meeting here, with other results leading researchers to suggest that seizure onset may be related to the entire puberty process.

Andrew G. Herzog, MD, and colleagues with Beth Israel Deaconess Medical Center in Boston conducted a cluster analysis of data on 1,144 women ages 18-47 from the web-based Epilepsy Birth Control Registry survey. Women were more likely to suffer their first seizure the same year as menarche than at any other age, they found.

Moreover, according to these self-reports, 49% of all initial seizures occurred from two years prior to menarche to six years afterwards -- essentially, the time-span of puberty.

In a statement, Herzog posited an explanation: "The levels of some hormones in the blood increase 10-fold during this time of life, including neuroactive steroids that affect the brain and make a seizure more likely."

"Menarche is really just a point in time," he told MedPage Today -- the point that most visibly signifies puberty. But the process begins much earlier and lasts much longer, he noted, and those hormones persist at a high level. "On top of this, menarche may aggravate the problem," added Herzog.

Women were four times more likely to suffer seizure onset during the year they experienced menarche, with 8.3% of the sample reporting their first seizure that year, versus an average 2% for each year the rest of their lives through age 47.

Women were two-and-one-half times more likely to suffer their first seizure during the eight-year puberty span than any other time of their life. "Clearly more seizures develop in girls during that period of time, so we need to begin looking at risk factors as well as potential treatments," Herzog said.

Boys also suffer more seizures during late-childhood and adolescence, Herzog said, another trend suggesting hormones are a factor for seizure onset in epilepsy.

"We need to look at the whole puberty process and this massive increase in hormone production," he said. "Hormones play a role and we've been neglecting it."

The next step, Herzog recommended, would be to conduct animal studies. Ultimately, he said, better understanding of the hormonal role in seizure disorders could lead to new treatments.

Mean age of menarche for women in this study was 12.55 years, with 13 being the most common (26%); the range was age 8-20. That mean was essentially identical to the average for non-epileptic women, which Herzog and colleagues put at 12.54.

Mean age of seizure onset was 14.1, with 15 the most common (7.1%); the range was age 0-42.

Study limitations included its retrospective nature and reliance on participants' self-reports for much of the study data. Participation in the registry -- the primary aim of which is to develop information on safety, effectiveness, and availability of contraception in women with epilepsy -- is voluntary and open to anyone.