Prevalence of thyroid disease in patients with obstructive sleep apnea

Studies have suggested that ethnicity and environment may influence thyroid disease. We aim in this study to determine the prevalence of thyroid disease among Saudi (Arab) patients with laboratory-diagnosed obstructive sleep apnea (OSA) and the characteristics and predictors of thyroid disease associated with OSA.

Serum thyroid-stimulating hormone (TSH) and free-thyroxine (FT4) levels were measured in all patients referred to the sleep disorders center for an overnight sleep study. The levels were measured within 4 weeks of the sleep study. Type I attended polysomnography (PSG) was performed for all patients.

During the study period, 271 patients with OSA and a mean age of 48.7 ± 14.1 yr, a body mass index (BMI) of 37.7 ± 9.6 kg/m(2) and an AHI of 55.2 ± 37/hr as well as 76 non-OSA patients with a mean age of 40.8 ± 14.9 yr, a BMI of 33.7 ± 8.9 kg/m(2) and an AHI of 3.8 ± 3.1/hr underwent thyroid function tests. In the OSA patients, the prevalence of newly diagnosed clinical hypothyroidism was 0.4%, and the prevalence of newly diagnosed subclinical hypothyroidism was 11.1%. In the non-OSA patients, the prevalence of newly diagnosed clinical hypothyroidism was 1.4%, and the prevalence of newly diagnosed subclinical hypothyroidism was 4%. There were no cases of clinical or subclinical hyperthyroidism in the studied group. Female gender was the only predictor of clinical hypothyroidism.

In the OSA patients, the prevalence of newly diagnosed clinical hypothyroidism was low; however, subclinical hypothyroidism was common among patients with OSA.