Insomnia in people with epilepsy: A review of insomnia prevalence, risk factors and associations with epilepsy-related factors

Background: Insomnia is a common sleep complaint in the general population, and sleep loss may be a trigger for epileptic seizures. Objectives: To conduct a comprehensive review of the literature of insomnia symptoms and insomnia disorder, their prevalence and epilepsy-related risk factors in people with epilepsy (PWE). Methods: A PUBMED search was performed for articles indexed to June 2016 involving human subjects, excluding papers in languages other than English, Spanish and Portuguese and case reports. Eligible studies were those using a clear definition of insomnia and reporting quantitative data on prevalence rates and risk factors. The search included the following terms: insomnia, sleep disorder(s), sleep disturbance(s) and sleep-wake in the title and abstract; and epilep* in the title. 425 papers were reviewed and 31 were selected for the final analysis (21 adult and 10 paediatric). Twenty-one studies used a control group. Two reviewer authors independently extracted all data and a third author resolved disagreements. Results: Most studies were hospital-based, cross-sectional and evaluated convenience samples representing highly select populations. Various insomnia inventories were used. Fourteen assessed insomnia (10 in adults, four, children), but only five as primary outcome (none in children). Four evaluated insomnia disorder based on international classification criteria (International Classification of Sleep Disorders ICSD-2 in 3, and DSM-IV-TR, in 1). In adults, insomnia prevalence was 28.9-51% based on the Insomnia Severity Index 15 and 36-74.4% based on DSM-IV-TR or ICSD-2. The prevalence of insomnia in children was 13.1-31.5% using the Sleep Disturbance Scale for Children and 11% based on ICSD-2 diagnostic criteria. Compared to control groups, PWE usually had higher frequencies of insomnia symptoms and disorder. Insomnia was associated with greater impairment in quality of life and higher degree of depressive symptoms in several studies, and was inconsistently related to female gender, poor seizure control and antiepileptic drug polytherapy. In children, insomnia was associated with developmental delay, focal epilepsies and poor seizure control. Conclusion: Insomnia symptoms and insomnia disorder are highly prevalent among PWE based on a limited number of studies with variable inclusion criteria and methodology. Excessive daytime sleepiness (EDS) was not found to be related to insomnia disorder or symptoms, and the exclusion of individuals with EDS may explain the higher frequencies of insomnia found in some studies. Additional investigations are needed given the potential impact of insomnia on seizure control, mood and QOL in PWE.