Obstructive Sleep Apnea Related Symptom Prevalence in Patients with Headache Presented to Neurology Outpatient Clinic: Results of a Preliminary Study *

Approximately 20% of patients with sleep apnea will have headaches and 25% of patients with other sleep disorders will also experience headaches. We aim to evaluate sleep apnea related symptom prevalence in patient with headache presenting to neurology outpatient clinics. Twenty four patients with headache were asked for sleep apnea symptoms. The prevalence of snoring, excessive daytime sleepiness and witnessed apnea was 33.3%, 20.8% and 4.2%, respectively. Among sleep apnea symptoms, the presence of at least one symptom, at least two symptoms and all three symptoms were 9 (37.5%), 4 (16.7%) and 1 (4.2%), respectively. The frequency of major symptoms of sleep apnea syndrome was high in patient with nonspecific headache. In the light of literature review, in case of a suspicion of sleep disorder in a headache patient, it would be appropriate to question the major symptoms of OSAS, and to refer the patient to a polysomnographic evaluation for an objective diagnosis. This approach would be helpful to improve the quality of life of patients with headache.


Introduction
Obstructive sleep apnea syndrom (OSAS) is a common sleep disorder of general population, with an estimated prevalence of 2% and 7% in adult population [1].It can be defined as repeated episodes of obstructive apneas and hypopneas during sleep, frequently followed by transient hypoxemia, hypercapnia, sleep fragmentation, unconscious arousals, and daytime sleepiness, which can lead to various somatic and mental problems.Thus, the severity of the symptom includes the combination of the severity of daytime sleepiness, and the value of apnea-hypopnea index (AHI) [1] [2].
While OSAS causes sleep fragmentation due to snoring and body movements between the apneic events, as well as the apnea periods, it can severely impair the quality of life of patients suffering from the disease [3].Common daytime effects of OSAS include excessive daytime sleepiness, irritability, decreased cognition, personality and mood changes such as depression or anxiety, and headaches [4].
Headache is one of the neurological manifestations of OSAS and irrespective of diagnosis; chronic daily, morning, or "awakening" headache patterns are soft signs of a sleep disorder.Sleep apnea headache may emerge de novo or may present as an exacerbation of cluster, migraine, tension-type, or other headache [5].The possible mechanisms underlying the pathogenesis of headache in OSAS are night-time fluctuations of oxygen saturation during the night with hypercapnia, vasodilatation, increased intracranial pressure and impaired sleep quality.However, the exact mechanisms of headache pathogenesis in the disease remain controversial [6] [7].
In the light of literature knowledge revealing the relationship between OSAS and headache, we aim to determine the obstructive sleep apnea symptom prevalence in patients with headache presenting to neurology outpatient clinic.

Materials and Methods
Patients with a new and/or prior diagnosis of headache who admitted to the neurology outpatient clinic of Duzce Medical Faculty Hospital were enrolled the study.All participants were informed about the content of the study and gave their written approval.Socio-demographic characteristics were obtained in a structured interview using an open questionnaire completed in person with all participants.
Headache assessment was made with a face-to-face interview in our neurology outpatient clinic.The patients who presented with a headache complaint were asked about the characteristic features of their headaches in order to make accurate diagnosis and the diagnosis of headache was made on the basis of the criteria of the International Classification of Headache Disorders, 2 nd edition (Headache Classification Subcommittee of the International Headache Society-IHS) [8].
Sleep disturbance in general and excessive daytime sleepiness were evaluated in all participants.The assessment of sleep disturbance was made with a questionnaire including major OSAS symptoms such as snoring (presence of snoring for at least 5 nights per week), witnessed apnea (spouse or relatives of patients with OSAS, identifying noisy and irregular snoring, and stopped respiration through the mouth and nose) and day time sleepiness, as well as minor symptoms (choking sensation during sleep, atypical chest pain, sleep split, insomnia, decreased ability to decide, concentration problems, palpitation, weight gain, personality changes, mood changes, abnormal motor activity during sleep, dry mouth, morning headaches, nocturnal cough and enuresis).
Epworth sleepiness scale (ESS) was used to evaluate excessive daytime sleepiness (Table 1).The questionnaire asks the subject to rate his or her probability of falling asleep on a scale of increasing probability from 0 to 3 for eight different situations that most people engage in during their daily lives, though not necessarily every day.The scores for the eight questions are added together to obtain a single number.A total score above 10 subjectively indicates excessive daytime sleepiness, which is accepted as a clinical feature of OSAS [9].
Data were organized in a SPSS version 19.0 (Statistical Package for Social Sciences for Windows) database.Statistical analyses were performed using the same program.Mean and standard deviation of data were calculated and descriptive analyses were performed.P values < 0.05 were considered to indicate statistical significance.
The answers of the questionnaire assessing the frequency of OSAS symptoms in patients with headache were shown in Table 2. Nine (37.5%) patients were experiencing major symptoms of OSAS, while fifteen (62.5%) had no complaints.Among the major symptoms, the prevalence of snoring was 33.3%, excessive daytime sleepiness was 20.8%, and witnessed apnea was 4.2%.When we assessed the co-existence of the major symptoms, we found that 37.5% (n = 9) of the patients were experiencing at least one major symptom of OSAS, while 16.7% (n = 4) had two symptoms, and 4.2% (n = 1) of the patients were suffering from three major symptoms OSAS (Table 2).
When we further analyzed the frequency of major OSAS symptoms according to the diagnosis of headaches in patients, we found that the major symptoms of OSAS were found to be more common in patients with nonspecific headaches (Table 3).

OSAS is a common sleep disorder characterized by an obstruction in the airway resulting in continued breathing
effort but inadequate ventilation, leading to sleep fragmentation, excessive daytime sleepiness, mood and personality changes, cognitive insufficiency, and headaches as well [6].
Although the exact pathogenesis of headaches in OSAS is not clear, several hypotheses have been proposed to explain the relationship between OSAS and the occurrence of headache, particularly on awakening.Night-time fluctuations of oxygen saturation during the night with hypercapnia, vasodilatation, increased intracranial pressure and impaired sleep quality are all considered as contributing factors [5] [13].
In our study, most of the patients had unidentified, nonspecific headaches.This can be associated with the low education profile of the patients, who were insufficient to describe the characteristics of their headaches.Similar to our results, some reports revealed headaches with nonspecific features in OSAS patients, too [14] [15].
Among the patients with identified headaches, we found that the most common diagnosis was exacerbation of migraine headaches (16.6%), followed by tension-type headaches, and morning headaches, 12.5% and 4.2%, respectively.Despite our low rates, particularly in morning headaches, the most common headache type was reported as tension-type morning headaches with a prevalence of 18% -60% in previous studies [6] [11] [12] [16].
We couldn't detect any exacerbation of cluster headaches or chronic daily headaches in our patients, but a prevalence of 53.8% was reported for cluster headaches, which were approximately 8.4 times more common in OSAS, when compared with normal individuals [17].This rate was reported as 42.8% for chronic daily headaches in patients with OSAS, as well [18].While our results are the preliminary outcomes, it is possible to correlate our low rates of headaches with our small number of participants.
In our study, the frequency of major OSAS symptoms was 33.3% for snoring, 20.8% for excessive daytime sleepiness, and 4.2% for witnessed apnea.Similar to our results, habitual snoring was found to be 24% in OSAS patients with headaches, particularly chronic daily headaches [6] [19].Despite our results, excessive daytime sleepiness frequency in children with headache was reported as 5.83% in a previous study [20].
In the highlight of literature review, we shared the results of our study evaluating the frequency of major OSAS symptoms, which are undeniably common sleep disorders in general population, deteriorating the quality of life.However, our study is ongoing, and these are the preliminary outcomes, even they let us consider that even patients' nonspecific headaches should be assessed about the major OSAS symptoms, as well as specific headaches such as tension-type, migraine, and etc.Thus, in case of a suspicion of sleep disorder in a headache patient it would be appropriate to question the patient about major symptoms of OSAS, and to refer to a polysomnographic evaluation for an objective diagnosis.This approach would be helpful to improve the quality of life of patients with headache.

3 ) 4 )
Sitting inactive in a public place (e.g. a theater or a meeting) As a passenger in a car for an hour without a break 5) Lying down to rest in the afternoon when circumstances permit 6) Sitting and talking to someone 7) Sitting quietly after a lunch without alcohol 8) In a car, while stopped for a few minutes in traffic Total Score

Table 2 .
Frequency of major OSAS symptoms in patients with headache.

Table 3 .
The frequency of major symptoms in headache patients with specific and nonspecific etiology.