Subclinical hypothyroidism as an independent predictor of obstructive sleep apnea diagnosed by home sleep apnea testing in adults with type 2 diabetes mellitus: A single-centre cross-sectional study from Bangladesh

Abstract

Background: Obstructive sleep apnea (OSA) and subclinical hypothyroidism (SCH) are both common among adults with type 2 diabetes mellitus (T2DM), but whether SCH independently predicts objectively diagnosed OSA is unclear. Objective: To determine whether SCH independently predicts OSA, diagnosed by home sleep apnea testing (HSAT), in adults with T2DM. Methods: In this single-centre cross-sectional study, 260 consecutive adults with T2DM were enrolled over 20 months in Tangail District, Bangladesh. Sample size (minimum 242) was calculated a priori to estimate SCH prevalence with 4.5% precision. Participants underwent standardized clinical, anthropometric, and biochemical assessment; completed Bangla versions of the STOP-Bang questionnaire and the Epworth Sleepiness Scale (ESS); and underwent overnight HSAT. Multivariable logistic regression identified independent predictors of moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥15 events/hour). Results: SCH was newly diagnosed in 42 of 260 patients (16.2%). Mean AHI was higher in the SCH group than in the euthyroid group (19.8 ± 9.4 vs. 12.4 ± 8.1 events/hour, p<0.001). The distribution of OSA severity across all four categories differed significantly between groups (p=0.035), with moderate-to-severe OSA present in 50.0% of the SCH group versus 27.5% of the euthyroid group. After adjustment for age, sex, body mass index (BMI), neck circumference, glycated haemoglobin (HbA1c), diabetes duration, and hypertension, SCH remained an independent predictor of moderate-to-severe OSA (adjusted odds ratio [aOR] 8.25, 95% confidence interval [CI] 3.18–21.38, p<0.001). Serum thyroid-stimulating hormone (TSH) was positively associated with AHI in linear regression. A STOP-Bang score ≥5 identified moderate-to-severe OSA with 80.1% specificity, compared with 30.8% specificity of a score ≥3 for identifying any OSA. Conclusion: SCH was independently associated with more severe, objectively diagnosed OSA in adults with T2DM, an association only partly explained by adiposity. Given the small SCH subgroup and single-centre design, these findings are hypothesis-generating and require confirmation. [J Assoc Clin Endocrinol Diabetol Bangladesh, January 2027; 6 (1): e91778]