Sleep, headache and sleep breathing disturbances: a polisomnographic study

Excerpt

Migraine is a primary disabling headache which impact on daily life is particularly relevant in case of a high frequency of attacks. Sleep and its disorders are known elements able to influence migraine frequency. Among sleep disorders breathing disturbances such as obstructive sleep apnea syndrome seems to the most relevant in modifying migraine course. Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent episodes of apnea during sleep that may induce a reduction in oxygen saturation possibly dangerous for the brain particularly when apneas are frequent and prolonged. The diagnosis of OSAS is based on clinical elements and instrumental evaluation. Nocturnal respiratory polygraphy (PoliSomnoGram PSG) is the diagnostic tool used to confirm OSAS diagnosis by the assessment of the apnea-hypopnea index (AHI) and oxygen desaturation index (ODI). In fact OSAS is diagnosed in the case of AHI > 5 in the presence of OSAS symptoms or when AHI > 15. Sleep breathing disorders may worsen a preexisting primary headache but it is also able to induce a specific secondary headache namely “OSAS headache,” characterized by morning diffuse and not a pulsating headache which generally does not require analgesic intake present more than 15 days per month not associated with nausea vomit phonophobia and photophobia. The presence of headache in a patient with OSAS does not mandatorily coincide with a diagnosis of OSAS headache: as said also primary headaches may be influenced and modified by OSAS. The differential diagnosis between OSAS headache and another form of head pain in a patient with OSAS is not always easy and the way to differentiate among subjects with OSAS and recurrent headache which ones had a preexisting primary headache and which ones developed a secondary headache induced by sleep apneas is frequently misunderstood. In order to make the diagnostic process easier and to clarify the reciprocal interference of sleep breathe and headache we studied polisomnographic parameters sleep behavior and headache characteristics in outpatients of the Headache Center and Sleep Disorders Center of the L. Sacco Hospital in Milan. Using an ad hoc questionnaire we investigated characteristics of sleep—defined as sleep onset latency sleep fragmentation and snoring—and of headache if present. Headache diagnosis was done according to the ICHD-III criteria. OSAS diagnosis was posed according to the International Classification of Sleep Disorders 2005. Using PSG we measured the apnea-hypopnea index (AHI) that is the number of apnea and hypopnea episodes per hour the oxygen desaturation index (ODI) which represents the number of episodes per hour with oxygen saturation reduced of at least 4% with respect to the basal SaO₂ the T90 namely the time with SaO₂ lower than 90% the mean SaO₂ during sleep and the entity of snoring. The t test was used to compare mean values of parameters between groups and the χ² test was applied to compare the distribution of a variable between different groups. A cohort of 184 subjects (114 F and 70 M) underwent a nocturnal respiratory polygraphy. Out of these 43 were free from any kind of headache (non-headache controls) 24 had a diagnosis of non-migraine headache (2 OSAS headaches 7 cluster headaches 16 tension-type headaches) and 117 had a migraine. Among migraineurs 32 had migraine with aura (MA)—of which 16 had a chronic form (ChMA) whereas 83 reported migraine without aura (MO) —of which 43 chronic (ChMO). Independently by the average BMI of groups a lower AHI was found in headache patients with respect to non-headache subjects (respectively 8.3 vs 22.6; p < 0.01 at t test) and in migraine patients with respect to non-migraine headachers (AHI 7.6 vs 11.6 p = 0.05 at t test) and non-headache subjects (AHI 7.6 vs 22.6 p < 0.001 at t test) especially in chronic migraine with respect to episodic (AHI 5.7 vs 9.6 p = 0.015 at t test). Also OSAS diagnosis was less frequent (p = 0.009 at χ² test) in chronic (24 out of 60; 40%) than in episodic migraine (37 out of 58; 67%). Sleep resulted more frequently fragmented among chronic migraineurs than in episodic (45 out of 53 vs 34 out of 51 p = 0.03 at χ² test) especially when allodynia was present and in parallel AHI was lower in OSAS patients with fragmented sleep than in patients without recurrent awakenings (16.10 vs 21.91; at test p = 0.05). Moreover among OSAS patients chronic allodynic migraineurs were the ones with the better breathing during sleep time. OSAS may be a causal element of migraine chronification: in fact also non-migraine attacks appear in a preexisting migraine that is the most frequent headache found in OSAS patients and among OSAS patients migraineurs especially chronic allodynic are the ones with better respiratory parameters. Based on these considerations it may be conceivable that when sleep apneas appear in a migraine patient migraine may reduce the severity of breathing pathology inducing sleep fragmentation. In turn OSAS worsening may increase migraine frequency in order to counteract more efficaciously apneas through an augmented sleep disruption. From these results migraine seems to be an allostatic strategy to reduce sleep breathing disorders …