Morning headache in habitual snorers.

Morning headache is regarded as a ‘red flag’ alerting clinicians to a potential underlying sleep disorder. Morning headache has been most frequently associated with obstructive sleep apnea and ‘sleep apnea headache’ is the only headache secondary to a sleep disorder recognized by the diagnostic criteria of the International Classification of Headache Disorders 2nd Edition (ICHD-2). However, the sensitivity and specificity of morning headache to predict sleep apnea is uncertain. Insomnia and a wide variety of other sleep disorders have been associated with morning headache as well, while psychiatric disorders are comorbid with both headache and sleep disorders. The report by Chen and colleagues (1) advances our understanding with a well-designed prospective study of morning headache in habitual snorers considering predictors and functional impairment of morning headache. Morning headache (also known as awakening headache) is the most common headache descriptor in clinical and epidemiological studies of sleep-related headache, generally referring to any form of headache that is proximally related to sleep. Morning headache emerges during sleep or upon awakening, and differs from chronic daily headache in that morning headache tends to remit after an interval of being awake rather than being unremitting. Morning headache patterns are often considered to be potential markers for a sleep disorder. Unfortunately, most studies of sleep related headache have not followed ICHD-2 criteria for sleep apnea headache or other standardized headache diagnostic criteria. Thus, the reliability of diagnosis is unknown. Inconsistencies in headache diagnosis limit generalizability across studies and probably account for at least some of the conflicting outcomes reported in the literature. Previous studies have noted a prevalence of morning headache in 4–6% of the general population, 18–60% of sleep apneics, 18% of insomniacs, and 21% of depressed individuals across studies (2). Chen et al. (1) found that 23.5% of a sample of 268 habitual snorers presenting for evaluation to a sleep disorder center had morning headache. Interestingly the 23.5% of snorers with morning headache showed greater functional impairment across all domains of social, physical, role and emotional impairment after controlling for sleep disorders, including obstructive sleep apnea, age, gender, psychological distress, BMI, migraine diagnosis, and smoking. Of total sample of 268 snorers, 43% (n1⁄4 116) had insomnia and 72% (n1⁄4 193) had elevated scale scores suggesting psychological distress. Thus, morning headache appears to be a significant symptom in its own right and should alert one to potential functional impairment. Headache has been associated with a wide range of sleep disorders in epidemiological and case-control studies reviewed elsewhere, including obstructive sleep apnea, insomnia, circadian rhythm disorders, movement disorders (e.g. restless legs syndrome, periodic limb movements), and parasomnias (2,3). Likewise, obesity and snoring as well as sleep disturbance have been identified as risk factors for progression from episodic migraine to chronic daily headache (4,5). Chen et al. (1) observed that habitual snorers with sleep apnea were indeed significantly more likely to have morning headache (27.2%) than snorers without sleep apnea (15.5%). Headache characteristics did not differ between morning headache patients with and without sleep apnea. Although sleep apnea is generally the sleep disorder most closely associated with morning headache, the adjusted odds ratio (adjusted for age, gender, smoking habits, and BMI) for sleep apnea (AOR1⁄4 2.6) was actually less in the case of sleep apnea than for other predictors including migraine (6.5), insomnia (4.2), and psychological distress (3.9). Interestingly, BMI was not a significant predictor of morning headache (1.6). Data indicate that sleep apnea is neither necessary nor sufficient for morning headache, even among a sample of habitual snorers. In fact, the data suggest that migraine was the most