The timing of seizures may be linked to natural rhythms in around 80% of people with epilepsy, according to the largest study of individual patients’ seizure cycles including more than 1,000 people, published in The Lancet Neurology journal.
Most people’s seizures occurred in a circadian (ie, 24-hour) rhythm, but some people experienced weekly and 3-weekly cycles in their seizures, and some had a combination of daily, weekly or longer cycles associated with their seizures.
While seizure patterns are known to vary over days, months and years, previous studies have been short-term or in small groups. The new study gives robust evidence of seizure cycles, showing that they are patient-specific and more common than previously thought.
“Understanding the cyclic nature of diseases is vital for treating diseases like epilepsy that continuously fluctuate in their severity,” says senior author Professor Mark Cook, The University of Melbourne, Australia. “The human body is a collection of thousands of clocks, each cycling in accordance with their own pacemaker. For example, some cells can track time with millisecond accuracy, while hormonal cycles might have longer periods of hours, days or more. Combined in the body, the presence of all of these cycles has a fundamental effect on our health.”
The link between epileptic seizures and other natural cycles has been studied for hundreds of years, and some now-disproven historical hypotheses suggested a link between the phases of the moon and seizure rates. More recently, the possible links have included associations with stress levels, seasonal variations in sleep quality, and other biological processes involved in sleep, menstruation and hibernation.
The new study used data from a seizure tracking website and mobile phone app with which 1118 patients with epilepsy recorded and tracked their seizures, and from a small study in which 12 people with epilepsy had a device fitted that recorded the electrical activity in their brain. The authors looked at the data for seizure frequency between six hours and three months, using statistical analysis to identify trends in individual patients’ seizure cycles. The study only included people who had frequent seizures.