Sleep Breath DOI 10.1007/s11325-014-0966-0
Relationship between sleep apnea and thyroid function Shoko Takeuchi & Takuro Kitamura & Toyoaki Ohbuchi & Hiroki Koizumi & Risa Takahashi & Nobusuke Hohchi & Hideaki Suzuki
Received: 1 October 2013 / Revised: 31 January 2014 / Accepted: 24 February 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose Sleep apnea is sometimes associated with hypothyroidism, but the significance of thyroid function screening in sleep apnea patients has been controversial. In the present study, we investigated the relationship between thyroid function and sleep apnea in subjects who were suspected to have sleep apnea. Methods We enrolled 156 consecutive subjects suspected of having sleep apnea. Subjects included 117 men and 39 women aged 21 to 84 years. They underwent nocturnal multichannel polysomnography during a one-night hospitalization. The examined indices of sleep apnea were apnea–hypopnea index (AHI), lowest oxygen saturation, oxygen desaturation index, longest apnea duration, mean apnea duration, and the percent of apnea time to sleep time. Serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were concomitantly measured by electrochemiluminescence immunoassays. Results Three subjects (1.9 %) were diagnosed with primary hypothyroidism (high TSH and low FT4), and one subject (0.6 %) with subclinical hypothyroidism (high TSH and normal FT4). No significant difference in the level of TSH, FT3, or FT4 was seen among subjects with different severity of sleep apnea. The mean apnea duration significantly correlated with TSH in both simple and multiple regression analyses. Subjects with lower FT3 (≤3.75 pg/ml) showed longer mean apnea time compared to those with higher FT3 (>3.75 pg/ml)
Shoko Takeuchi and Hideaki Suzuki equally contributed to this work. S. Takeuchi : T. Kitamura : T. Ohbuchi : H. Koizumi : R. Takahashi : N. Hohchi : H. Suzuki (*) Department of Otorhinolaryngology-Head and Neck Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan e-mail: [email protected]
(24.9±0.8 vs. 20.2±1.2 s; P=0.009). The other indices of sleep apnea did not show significant correlation with thyroid function. Conclusions These results suggest that the mean apnea duration and TSH/FT3 may be helpful in understanding reciprocity between the two disease states, and for evaluating the validity of thyroid function tests in patients with sleep apnea. Keywords Sleep apnea . Thyroid function . Thyroid-stimulating hormone . Triiodothyronine . Thyroxine . Mean apnea duration
Introduction Patients with sleep apnea and those with hypothyroidism share several common clinical features, including apathy, lethargy, fatigue, loss of ambition, and excessive daytime somnolence [1, 2]. It has been well known since the 1980s that sleep apnea is sometimes associated with hypothyroidism. High prevalence of sleep apnea in patients with hypothyroidism has been reported by several researchers [1, 3, 4], and the participation of thyroid function in the pathogenesis of sleep apnea attracted the attention of researchers in this field in the 1980s and 1990s. However, it is also true that hypothyroidism is seen only in a small proportion of patients with sleep apnea, and a number of authors have recently published skeptical reports on the significance of routine thyroid function screening in sleep apnea patients [5–8]. Other authors, however, still argue certain significance for the thyroid function test in sleep apnea [9–11]. In the present study, we investigated the relationship between thyroid function and sleep apnea in subjects who were suspected of having sleep apnea.
One hundred and fifty-six consecutive subjects who visited our department between January 2011 and January 2013 and were suspected of having sleep apnea were enrolled. They were 117 male and 39 female participants, ranging in age from 21 to 84 years with an average of 52.9 years. The body mass index (BMI) ranged from 14.2 to 46.5 kg/m2 with an average of 27.1 kg/m 2 . Tonsillar hypertrophy (grade 2–3 in Mackenzie’s classification) and nasal septal deviation were seen in 29 and 59 subjects, respectively. There were 62, 36, 15, and 14 subjects who had hypertension, diabetes mellitus, cardiac disease, and cerebrovascular disease, respectively. One subject had previously been diagnosed with hypothyroidism but had not received thyroid hormone replacement therapy. The other 155 subjects had no previous diagnosis of hypothyroidism. Subjects underwent nocturnal multichannel polysomnography during a one-night hospitalization using the Alice-5 Polysomnography System (Respironics Inc., Pittsburgh, PA). Electrocardiogram, electroencephalogram (C3A2; C4-A1; O1-A2; O2-A1), electrooculogram (two channels), and submental/anterior tibial electromyograms were recorded using surface electrodes. Respiratory airflow was measured with a nasal pressure cannula and an oronasal thermistor placed at the nostril and mouth. Thoracic and abdominal movements were monitored by a plethysmograph, while oxygen saturation (SpO2) was measured by a finger pulse oximeter. Sleep stages were manually scored in 30-s epochs according to Rechtschaffen and Kales , and respiratory events were scored according to the 2007 American Academy of Sleep Medicine (AASM) scoring rules . Obstructive apneas were defined as the cessation of nasal pressure and oronasal thermistor for ≥10 s with continuing abdominal and thoracic movements. Obstructive hypopneas were defined as ≥50 % reduction in nasal pressure for ≥10 s, compared with baseline, accompanied by abdominal and thoracic movements in combination with an arousal or an oxygen desaturation of ≥3 %. The obstructive apnea–hypopnea index (AHI) was defined as the mean number of obstructive apneas and hypopneas per hour of sleep. The severity of sleep apnea was classified into four categories: non-apneic (AHI