Sleep patterns and stress display link to epileptic seizures -

BIRMINGHAM, United Kingdom — Scientists from the University of Birmingham have uncovered a potential link between sleeping patterns, stress hormones, and the occurrence of seizures in people with epilepsy. Researchers used math to delve into the impact of various physiological processes, including sleep and fluctuations in the stress hormone cortisol, on the distinct markers of epilepsy, known as epileptiform discharges (ED).

Epilepsy is a severe neurological disorder characterized by recurrent, spontaneous seizures. Traditionally, doctors believed seizures happen randomly. However, the discovery of ED activity with varying timescales, spanning from hours and days to months, has challenged this assumption.

In their investigation, scientists analyzed 24-hour EEG (electroencephalogram) recordings from 107 individuals with idiopathic generalized epilepsy. Their analysis unveiled two distinct subgroups within the study population, each displaying different distributions of epileptiform discharges: one with a higher incidence during sleep and the other during daytime.

The study indicates that the dynamics of cortisol, the transition between sleep stages, or a combination of both, explained most of the observed distributions of ED.

“Some 65 million people have epilepsy worldwide, many of whom report specific triggers that make their seizures more likely – the most common of which include stress, sleep deprivation and fatigue,” says study lead author Dr. Isabella Marinelli, from the University of Birmingham’s Center for Systems Modeling & Quantitative Biomedicine (SMQB), in a university release. “Our findings provide conceptual evidence that sleep patterns and changes in concentration of cortisol are underlying physiological drivers of rhythms of epileptiform discharges. Our mathematical approach provides a framework for better understanding what factors facilitate the occurrence of ED activity and potentially trigger the seizures which can be so debilitating for epilepsy sufferers.”

Researchers developed a mathematical model that describes the activity of interconnected regions within the brain and how the excitability of these regions can change in response to various stimuli. These stimuli include transitions between sleep stages or fluctuations in cortisol concentration.

It was noted that the frequency of ED increases during the night, particularly in the early morning and during stressful situations in many individuals with epilepsy. The study revealed that sleep played a crucial role, accounting for 90 percent of the variation in one subgroup, while cortisol contributed to approximately 60 percent in the other subgroup.

Cortisol, one of the primary stress hormones in humans, is produced and secreted under the control of the hypothalamic-pituitary-adrenal (HPA) axis. In stressful circumstances, activity in the HPA-axis rises, leading to an increased secretion of cortisol.

“Sleep alone cannot account for the changes in ED likelihood during wakefulness observed in our first subgroup. There is a reduction in ED likelihood during the sleep time after an initial sharp increase during the first hours,” explains Dr. Marinelli. “This can be explained by the fact that deep sleep, which is linked to an increase of EDs, is predominant during the first third of the sleep period. We found an increase in ED occurrence before waking, which – given that the level of cortisol is known to increase around waking – suggests a combined effect of sleep and cortisol.”

The study is published in the journal PLoS Computational Biology.