In recent years, a surge of studies has addressed the important and complex relationship between epilepsy and sleep. A review published in Epilepsy and Behavior explored the recent developments and highlighted areas where more research is needed in this field of study.
Sleep is an important component in the disease state of epilepsy because 10% to 15% of seizures are sleep related and more than 90% of sudden unexpected deaths in epilepsy occur during sleep. Seizure locations have been associated with significant circadian rhythms. Frontal lobe seizures are more likely to occur during sleep or in the early morning, and mesial temporal seizures are more likely during the morning or late afternoon. Occipital seizures rarely occur during sleep and peak during early evening.
Sleep/wake disorders are diagnosed at a rate 2 to 3 times higher among patients with epilepsy than in the general population, with hypersomnia being particularly common. Other frequent problems include insomnia, restless legs syndrome, and sleep bruxism as well as sleep disordered breathing. These problems are an issue among this patient population because poor sleep quality has been associated with decreased seizure control. Treating sleep apnea reduces seizures for many patients.
Patients who have genetic generalized epilepsies, especially juvenile myoclonic epilepsy (JME), are at increased risk for poor seizure control during periods of sleep deprivation. Those with JME, especially if they are adolescents, are more likely to have decreased frontal executive functions, increasing the likelihood of maintaining unhealthy sleep habits.
Generalized and focal interictal epileptiform discharges during sleep were most likely to occur during non-rapid eye movement (NREM) 3, NREM 1, or NREM 2 sleep periods, and unlikely to occur during REM sleep. These discharges were associated with sleep fragmentation among most patients.
An important function of NREM sleep is to consolidate memory and learning. A study of verbal memory over 1 week found a negative correlation with hippocampal spike frequency during sleep that may be due to seizure interruption of hippocampal-neocortical transfer of information during NREM sleep.
Findings indicated that gaps in knowledge remain regarding the complex bidirectional relationship of sleep and epilepsy. The review authors concluded, “New developments and directions in understanding the bidirectional relationships between sleep and epilepsy will encourage clinicians to consider the impact of sleep (or lack of it) in people with epilepsy and researchers [to] explore what we still need to know.”
Grigg-Damberger M, Foldvary-Schaefer N. Bidirectional relationships of sleep and epilepsy in adults with epilepsy. Epilepsy Behav. Published online February 6, 2021. doi:10.1016/j.yebeh.2020.107735