Review articleInsomnia in people with epilepsy: A review of insomnia prevalence, risk factors and associations with epilepsy-related factors
Introduction
Epilepsy is a brain disorder characterized by an enduring predisposition to generate epileptic seizures with consequences on neurobiological, cognitive, psychological, and social performance (Fisher et al., 2014). Sleep-wake complaints are at least twice as common in people with epilepsy (PWE) compared with the general population (Gutter et al., 2013, Jain et al., 2013, Xu et al., 2006) and comorbid sleep disturbances have been associated with additional impairment in quality of life (QoL) (de Weerd et al., 2004, Garcia-Morales et al., 2014, Gutter et al., 2013, Piperidou et al., 2008, Vendrame et al., 2013), worsening seizure control (Batista and Nunes, 2007, Piperidou et al., 2008) and psychiatric conditions (Vendrame et al., 2013).
Insomnia symptoms and disorders are exceedingly common in the general population with a prevalence of 35–50% and 12–20%, respectively, sometimes due to comorbid medical or psychiatric conditions, medications or substance use (Buysse, 2013, Sateia, 2014). Known risk factors include female gender, older age, lower socioeconomic status, comorbid psychiatric and medical conditions, substance abuse, unemployment, divorce and widowhood (Buysse, 2013). Insomnia is a known risk factor for the development of depression and anxiety, as well as to impaired QoL and people with insomnia are at risk for a number of adverse health outcomes including hypertension, diabetes, and cardiovascular events (Buysse, 2013, Lewis et al., 2014, Sofi et al., 2014, Vgontzas and Fernandez-Mendoza, 2013). Untreated insomnia has an impact in health care economics, with direct costs (outpatient encounters, drug prescription, cognitive behaviour therapy, procedures) and indirect costs (lost workplace productivity, higher accident risks) exceeding 100 billion dollars annually in the USA alone (Ohayon, 2002, Wickwire et al., 2015). Despite this burden and the high costs, insomnia is still undervalued by most health professionals and patients (Buysse, 2013, Manni and Terzaghi, 2010, Ohayon, 2002).
The relationship between sleep and epilepsy have been explored in previous studies and the existence of a detrimental effect of sleep deprivation on epileptiform activity is undeniable (Derry and Duncan, 2013, Manni and Terzaghi, 2010). Moreover, sleep disorders are common in PWE, possibly due to the sleep disruption lead by the occurrence of an epileptic attack or as a consequence of antiepileptic drug therapy (AED) (Manni and Terzaghi, 2010). However, little research was performed to assess insomnia in epileptic population, therefore prompting a literature review of the prevalence of insomnia disorder and symptoms in PWE, as well as to identify possible risk factors related to this comorbid sleep disorder.
Section snippets
Methods
A PUBMED search was performed to identify publications involving human subjects with epilepsy exploring sleep-wake disorders and complaints through June 2016 (Fig. 1). This search used the terms insomnia, sleep disorder(s), sleep disturbance(s) and sleep-wake in title and abstract; and epilep (sy,tic), in the title, but not in different languages other than English, Spanish and Portuguese. Case reports were excluded. Abstracts were reviewed by two investigators (PJOMM and PSO) for data
Results
Of 425 studies screened for inclusion, 31 (21 adult, 10 paediatric) fulfilled the inclusion criteria (Table 1, Table 2). Twenty articles compared outcomes between PWE and controls (Babu et al., 2009, Batista and Nunes, 2007, Chan et al., 2011, Chen et al., 2011, de Weerd et al., 2004, Gutter et al., 2013, Hoeppner et al., 1984, Im et al., 2016, Ismayilova et al., 2015, Khatami et al., 2006, Krishnan et al., 2012, Larson et al., 2012, Ng and Bianchi, 2014, Ong et al., 2010, Pizzatto et al., 2013
Discussion
Studies in adults with epilepsy show that the frequency of insomnia varied widely and was usually higher than those found in nonepileptic subjects (Chen et al., 2011, de Weerd et al., 2004, Hoeppner et al., 1984, Im et al., 2016, Ismayilova et al., 2015, Khatami et al., 2006, Krishnan et al., 2012, Pizzatto et al., 2013, Yazdi et al., 2013, Zhou et al., 2012). Most papers defined insomnia symptomatically and measures of insomnia severity were broadly used, such as insomnia inventories (Cobabe
Conclusions
Interest in the complex, reciprocal relationships between sleep and epilepsy has risen dramatically in recent years, but many questions remain. This is the first review of insomnia in PWE and it highlights the need for more research given the high prevalence of insomnia symptoms in PWE and the potential impact of insomnia on epilepsy-related outcomes. Methodological variability played an important role in this uncertainty, as those related to insomnia definition, population selection criteria,
Conflict of interest
The authors declare no conflicts of interest regarding this paper.
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