Sleeping patterns and stress hormones could be the key to understanding how and when people with epilepsy are likely to experience seizures, a new study reveals.
Researchers used mathematical modelling to understand the impact of different physiological processes, such as sleep and changes in concentration of the stress-hormone cortisol, on key signatures of epilepsy – known as epileptiform discharges (ED).
Epilepsy is a serious neurological disorder characterised by a tendency to have recurrent, spontaneous seizures. Classically, seizures were assumed to occur at random, until the discovery of ED activity with timescales that vary from hours and days through to months.
The scientists analysed 24-hour EEG recordings from 107 people with idiopathic generalized epilepsy and discovered two subgroups with distinct distributions of epileptiform discharges: one with highest incidence during sleep and the other during daytime.
Publishing their findings in PLOS Computational Biology, the international research team led by the University of Birmingham, reveal that either the dynamics of cortisol or sleep stage transition, or a combination of both, explained most of the observed distributions of ED.
Lead author Isabella Marinelli, from the University of Birmingham’s Centre for Systems Modelling & Quantitative Biomedicine (SMQB), commented:
The researchers’ mathematical model describes the activity of connected brain regions, and how the excitability of these regions can change in response to different stimuli - either transitions between sleep stages or variation in concentration of cortisol.
ED frequency increases during the night, early in the morning, and in stressful situations in many people with epilepsy. The team discovered that sleep accounted for 90% of variation in one subgroup and cortisol around 60% in the other subgroup.
Cortisol is one of the primary stress hormones in humans, with production and secretion controlled by the hypothalamic-pituitary-adrenal (HPA)-axis. In stressful situations, HPA-axis activity increases, resulting in a higher secretion of cortisol.