Incidence of hypothyroidism and its correlation with polysomnography findings in obstructive sleep apnea

The aim of this study is to investigate the thyroid functions and its correlation with polysomnography findings in obstructive sleep apnea patients. This study was conducted on 203 patients evaluated with the complaints of snoring, witnessed apnea and daytime sleepiness and established polysomnography (PSG) indication between May 2008 and August 2011. All patients' nocturnal PSG recordings were carried out. The thyroid function was classified as euthyroid, subclinical hypothyroidism and clinical hypothyroidism after analyzing serum TSH and free T4 values. The correlation between the data obtained from PSG records and thyroid function values was statistically compared. Apnea hypopnea index obtained from PSG was in the range of 5.4-132.9/h, and mean value was 32.7/h. The lowest oxygen saturation level was in the range of 20-92 %, and the mean value was 76.4 %. According to PSG results, 55 patients (27.09 %) had mild obstructive sleep apnea syndrome (OSAS), 48 patients (23.65 %) had moderate OSAS and 100 patients (49.26 %) had severe OSAS. On evaluation of the thyroid function test results, 10.8 % (n = 22) of the patients were defined to have subclinical hypothyroidism and 1.97 % (n = 4) clinical hypothyroidism. We found a total of 12.77 % subclinical and clinical hypothyroidism in patients with OSAS. Though the incidence of hypothyroidism was pretty high in patients with OSA, there was no statistically significant correlation between thyroid functions and polysomnography findings. We suggest that evaluation of the thyroid functions is important and necessary in patients with OSAS. Polysomnography findings do not correlate statistically with thyroid function tests, addressing the need for thyroid screening for all OSAS patients.