Letter to the Editor Cephalalgia 0(0) 1–2 ! International Headache Society 2017 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0333102417731354 journals.sagepub.com/home/cep
Comment on: Excessive daytime sleepiness in chronic migraine and chronic tension-type headache from the general population To the editor: We have read the articles ‘‘Excessive daytime sleepiness in chronic migraine and chronic tension-type headache from the general population’’ by Kristoﬀersen ES, et al. (1), published online ﬁrst in Cephalalgia, with great interest. The authors performed a cross-sectional survey of 30,000 people aged 30–44 (323 eligible participants with chronic headache) to investigate the association between headache, especially chronic migraine (CM) or chronic tension-type headache (CTTH) and excessive daytime sleepiness (EDS). The authors concluded increased EDS was associated with higher headache frequency, but not with speciﬁc headache diagnoses. There is the major strength that this study is a large population-based sample which was representative of the general population by the high response rate. However, we would like to make three comments about this study for the beneﬁt of the readers. First, authors described the participants’ information on socio-demographics, height, weight, smoking status, medication overuse, headache frequency and headache disability. However, they did not mention other conditions and diseases that can cause EDS such as snoring and obstructive sleep apnea (OSA). EDS is one of the most common symptoms in patients with snoring and OSA. OSA is by far the most common sleep disturbance of the general population, with an estimated prevalence of 2% and 7% in the adult population (2). Although there has been much controversy about the correlation between subjective EDS and objective polysomnographic ﬁndings, we think authors should consider whether the participants snore or have OSA, or not. Second, although headache may cause sleep disturbances including EDS, headaches may be inversely caused by OSA. So, we think that the relationship between headache and OSA should be considered. Headache prevalence due to OSA is estimated at 1–2% of the general population and aﬀects 2–8% of the middle-aged population (3). On the other hand,
there is no relation either between OSA and migraine or between OSA and TTH in the general population (4). Although there is still controversy, we suggest considerations should be given to the study of sleep disturbance in headache patients, since there is an association between headache and OSA. Third, the Epworth sleepiness scale (ESS) is a widely-used tool that subjectively measures EDS. It is a simple, self-administered questionnaire with an eightitem, four-point scale that investigates the possibility of a person falling asleep during various daily activities. However, we think there is a common methodological problem in previously reported studies, as follows. Most studies have used a cutoﬀ of 10 points on the ESS score, dichotomizing patients into those with and without EDS. In this context, investigators had to accept the assumption that patients with an ESS score of 11 had the same degree of EDS as those who had an ESS score of 24. In addition, studies might classify patients with an ESS score of either 10 or 11 to either the non-EDS or EDS groups, despite the diﬀerence in subjective score being one point out of the 24-point scale between these two groups of patients. So, it is recommended that clinicians be cautious when using ESS for the diagnosis of obstructive sleep apnea and determining the response to treatment. We suggest using more objective tools to measure EDS, such as the multiple sleep latency test (MSLT), may be useful in your further study. Fong et al. demonstrated that MSLT was better than ESS in the assessment of EDS in patients with OSA (5). Declaration of conflicting interests The authors declared no potential conﬂicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The authors received no ﬁnancial support for the research, authorship, and/or publication of this article.
References 1. Kristoffersen ES, Stavem K, Lundqvist C, et al. Excessive daytime sleepiness in chronic migraine and chronic tension-type headache from the general population.
Cephalalgia 0(0) Cephalalgia. Epub ahead of print 10 July 2017. DOI: 10.1177/0333102417721133. Merikangas KR, Zhang J, Emsellem H, et al. The structured diagnostic interview for sleep patterns and disorders: Rationale and initial evaluation. Sleep Medicine 2014; 15: 530–535. Russell MB. Sleep apnea headache: A growing concern in an increasingly obese population? Expert Rev Neuro 2013; 13: 1129–1133. Russell MB, Kristiansen HA and Kværner KJ. Headache in sleep apnea syndrome: Epidemiology and pathophysiology. Cephalalgia 2014; 34: 752–755. Fong SY, Ho CK and Wing YK. Comparing MSLT and ESS in the measurement of excessive daytime sleepiness in obstructive sleep apnoea syndrome. J Psychosom Res 2005; 58: 55–60.
Hyun Jin Min and Kyung Soo Kim Department of Otorhinolaryngology-Head and Neck Surgery, Chung-Ang University College of Medicine, Seoul, Korea Corresponding author: Kyung Soo Kim, Department of OtorhinolaryngologyHead and Neck Surgery, Chung-Ang University College of Medicine, 224-1, Heukseok-dong, Dongjak-gu, Seoul, Korea. Email: [email protected]