Headache and sleep: The missing links

Abstract

Headache and sleep obviously show several clinical links, and even in antiquity good sleep was thought to be a cure for headache and bad sleep was said to be a trigger for headache. In the paper by Lateef and co-workers (1), a particular aspect of these links has been investigated: the comorbidity of poor sleep, in particular different types of insomnia, with headache (separately for headache in general, migraine without aura, migraine with aura). The authors show that headache in general, but not specifically migraine without or with aura, is associated with an approximately twofold increased risk for insomnia. This confirms previous studies which also linked sleep disturbances to headache in general (2). The authors further speculate about the underlying reason for this association in three ways. It might be that subjects with headache have a pathophysiology leading to both headache and insomnia; it might be that sleep disturbances are a trigger for headache in general; and it might be that headache induces insomnia. The strength of this study lies in the large representative population-based patient sample, which were interviewed in the United States with a focus on one specific sleep disturbance, namely insomnia. However, the interview questions for migraine and in particular for the migraine aura were not very specific, and it is doubtful whether the different headache diagnoses are completely reliable (e.g. some aura subtypes were not included). Furthermore, the study defined increased daytime sleepiness as one aspect of insomnia, wheres it is classified as hypersomnia in the International Classification of Sleep Disorders (ICSD) (3) and might not only be a result of insomnia in the night but a result of other sleep disorders. The obvious links between headache and sleep have increasingly become part of headache rather than of sleep research. From a systematic point of view, we can differentiate the following aspects: