FREQUENCY OF OBSTRUCTIVE SLEEP APNEA (OSA) IN PATIENTS WITH HYPOTHYROIDISM

In the case of obstructive sleep apnea (OSA) the airways close either partially or completely, reducing the level of oxygen in the blood or causing the person to wake up, thus making it difficult to get a good night sleep as well as other symptoms such as loud snoring, apnea during sleep and excessive daytime sleepiness [1]. Obstructive sleep apnea (OSA) can negatively affect a person's risk of developing heart disease and mental illness, quality of life, and safe driving [2]. The prevalence of obstructive sleep apnea is estimated to be 28.7-43.8% among the population, and 37% in Asia, with there being millions who suffer from it. This has been associated with a myriad of other morbidities including hypertension, coronary artery disease, depression, insulin-resistant diabetes, and accidents during sleep, as a result of poor sleep quality [4]. The STOP-BANG score has received thorough research and has been proven to be a reliable tool for determining the problems associated with OSA. The STOP-BANG score is associated with an increased risk of cardiopulmonary complications by 4-fold in a meta-analysis [5]. A multitude of conditions may lead to obstructive sleep apnea, such as acromegaly, metabolic syndrome, chronic alcohol abuse, sedative use, advanced age, male sex, obesity, adenoid and tonsillar hypertrophy, mandibular hypoplasia, micrognathia and diabetes [6,7]. Other than these factors, another important etiology of obstructive sleep apnea is hypo-functioning of thyroid gland. In one study, it was reported that 18.6% of hypothyroidism patients had obstructive sleep apnea (OSA) [8]. This rate of obstructive sleep apnea (OSA) in hypothyroid patients was 12.3% in another study [9]. A similar study was carried out, and it was reported that only 9.47% of the patients in the study who were diagnosed with hypothyroidism had obstructive sleep apnea (OSA) which is significantly less than the above-mentioned study [10]. A few studies have shown that thyroid hormone replacement could improve sleep-related symptoms, but the link between hypothyroidism and OSA is not fully understood [11]. In addition, symptoms like fatigue, daytime somnolence, weight gain, and cognitive impairment are often shared by the two disorders and may be underdiagnosed in hypothyroid patients. [12] Owing to these highly variable results it is imperative to further conduct study with the aim of determining frequency of obstructive sleep apnea (OSA) in patients with hypothyroidism.

OBJECTIVES

To determine frequency of obstructive sleep apnea (OSA) in patients with hypothyroidism.

Data were collected from 132 patients, mean age was 45.8 ± 10.7 years, with an age range of 25–65 years. Females constituted the majority of the study population, accounting for 89 (67.4%) patients, while 43 (32.6%) were males. The mean BMI was 29.4 ± 4.8 kg/m², and the mean duration of hypothyroidism was 4.2 ± 2.8 years. The mean serum TSH level was 8.9 ± 4.6 mIU/L, while the mean fT4 and fT3 levels were 0.82 ± 0.21 ng/dL and 301.5 ± 52.8 pg/mL, respectively.

Table 1. Baseline demographic and clinical characteristics of patients with hypothyroidism (n=132)

Obstructive sleep apnea was diagnosed in 18 (13.6%) of the 132 hypothyroid patients, whereas 114 (86.4%) did not have OSA. Among patients with OSA, the mean apnea-hypopnea index was 18.7 ± 9.4 events per hour. Mild OSA was the most common severity category, affecting 8 (44.4%) patients, followed by moderate OSA in 6 (33.3%) and severe OSA in 4 (22.2%) patients.

Table 2. Frequency and severity of obstructive sleep apnea among hypothyroid patients (n=132)

Patients older than 45 years had a higher prevalence of OSA than those aged 45 years or younger (19.4% vs. 7.7%, p=0.041). OSA was more common among males compared with females (20.9% vs. 10.1%, p=0.048). Similarly, patients with BMI ≥30 kg/m² had a significantly higher prevalence of OSA than those with BMI <30 kg/m² (24.0% vs. 7.3%, p=0.011). Patients with hypothyroidism duration greater than five years also had a higher frequency of OSA compared with those having hypothyroidism for five years or less (28.1% vs. 9.0%, p=0.036).

Table 3. Stratification of OSA frequency according to age, gender, BMI, and duration of hypothyroidism (n=132)

Chi-square test was applied. A p-value of ≤0.05 was considered statistically significant.

Figure 1. Frequency of obstructive sleep apnea among patients with hypothyroidism

This is a cross-sectional study where obstructive sleep apnea (OSA) was found in 18 (13.6%) out of 132 patients with hypothyroidism. In the group of patients with a diagnosis of OSA, 8/23 (44.4%) patients had mild OSA, 6/23 (33.3%) moderate OSA, and 4/23 (22.2%) severe OSA. Increasing age, male gender, obesity, and longer duration of hypothyroidism were significantly associated with a higher frequency of OSA. The mean age of the study population was 45.8 ± 10.7 years and 67.4% of the subjects were females. The gender predominance is consistent with the epidemiology of hypothyroidism, which is more common in women, due to the higher prevalence of autoimmune thyroid disorders. But, even with the smaller number of males, OSA was significantly higher in males than females (20.9% vs 10.1%, p=0.048). The same results have also been observed in previous studies, which found that males are also an independent risk factor for OSA due to different upper airway structures, fat distribution and hormonal differences affecting respiration [13].

The overall prevalence of OSA found in this study is consistent with other studies that assessed sleep-disordered breathing in patients with hypothyroidism. Previous studies have found a prevalence from 9% to 25%, taking polysomnography selectively in high-risk subjects identified by screening questionnaires. However, research using universal polysomnography has found much higher rates, up to 80% [14]. These differences may be explained by differences in study population, definition of hypothyroidism, diagnostic criteria, and screening for OSA. There are several pathophysiological mechanisms that may account for the relationship between hypothyroidism and OSA. Thyroid hormone deficiency is also associated with upper airway narrowing by deposition of mucopolysaccharides in the tongue and pharyngeal tissues which results in macroglossia and soft tissue edema [15]. Also, hypothyroidism leads to upper airway dilator muscle myopathy, decreased ventilatory drive and decreased sensitivity to hypoxia and hypercapnia. Common symptoms of hypothyroidism are weight gain and obesity, which worsens sleep apnea by making the upper airway more collapsible [16].

This study showed that there was a significant correlation between obesity and OSA. The odds of having OSA were significantly greater in patients with BMI ≥30 kg/m2 than in patients with BMI <30 kg/m2 (24.0% vs. 7.3%, p=0.011). Obesity is a known risk factor for OSA as the excess adipose tissue in the neck and pharyngeal structures make the airway more resistant and prone to collapse during sleep. BMI is one of the most consistent predictors of the severity of OSA demonstrated in previous studies. Another important finding of the present study was the association between the duration of hypothyroidism and OSA [17]. The frequency of OSA was significantly higher in patients with hypothyroidism for more than 5 years compared with patients with a shorter duration of the disease (28.1% vs. 9.0%, p=0.036). Inadequate or untreated hypothyroidism for long periods of time can lead to progressive infiltration of soft tissue, persistent metabolic dysfunction, and a slow deterioration of the role of the upper airway muscles, which can contribute to sleep-disordered breathing. The findings of this study have important clinical implications [18]. Several symptoms are common for both hypothyroidism and OSA including fatigue, excessive daytime sleepiness, poor concentration and weight gain, and this can contribute to under-recognizing OSA in this population [19]. If OSA may be present in hypothyroid patients, early diagnosis and treatment can have a positive impact on quality of life and lessen the risk of cardiovascular side effects as well as insulin resistance and neurocognitive impairment [20]. There are a few limitations with this study. The cross-sectional design does not allow for the determination of cause and effect between hypothyroidism and OSA. Polysomnography was only performed in patients that had a STOP-BANG score of ≥5, which could have underestimated the actual prevalence of OSA. Moreover, the study was performed in one tertiary care centre on non-probability consecutive sampling, which might restrict the generalization of the results. Other factors that could have confounded the analysis, such as information on thyroid replacement therapy adherence, degree of thyroid dysfunction, neck circumference, etc. was not investigated. However, this study offers local insight into the prevalence of OSA in patients with hypothyroidism in Pakistan, despite the limitations mentioned above. Hypothyroid patients should be screened routinely for OSA with the use of simple screening tools like the STOP-BANG questionnaire, especially older males, obese people, and those with a longer duration of hypothyroidism.

Based on the results, it is concluded that OSA is a relatively common comorbidity in patients with hypothyroidism; 13.6% of the studied population had OSA. There was a significant association between longer duration of hypothyroidism, male gender, obesity, and increased frequency of OSA.The association with longer duration of hypothyroidism, male gender and obesity with increased frequency of OSA was significant. Mild OSA was the most common severity classification. Due to the clinical overlaps between hypothyroidism and OSA, regular screening, with the use of validated brief questionnaires (STOP-BANG), may aid early detection of high-risk patients. Early diagnosis and treatment of hypothyroidism patients could benefit the quality of life and decrease the long-term cardiovascular complications associated with OSA.

1.     Platon AL, Stelea CG, Boișteanu O, Patrascanu E, Zetu IN, Roșu SN, et al. An update on obstructive sleep apnea syndrome-a literature review. Medicina (Kaunas). 2023;59(8):e1459.

2.     Abbasi A, Gupta SS, Sabharwal N, Meghrajani V, Sharma S, Kamholz S, et al. A comprehensive review of obstructive sleep apnea. Sleep Sci. 2021;14(2):142-54.

3.     Ghavami T, Kazeminia M, Ahmadi N, Rajati F. Global prevalence of obstructive sleep apnea in the elderly and related factors: a systematic review and meta-analysis study. J Perianesth Nurs. 2023;38(6):865-75.

4.     Palomo JM, Piccoli VD, Menezes LM. Obstructive sleep apnea: a review for the orthodontist. Dental Press J Orthod. 2023;28(1):e23spe1.

5.     Pivetta B, Chen L, Nagappa M, Saripella A, Waseem R, Englesakis M, et al. Use and performance of the stop-bang questionnaire for obstructive sleep apnea screening across geographic regions: a systematic review and meta-analysis. JAMA Netw Open. 2021;4(3):e211009.

6.     Gottlieb DJ, Punjabi NM. Diagnosis and management of obstructive sleep apnea: a review. JAMA. 2020;323(14):1389-400.

7.     Charčiūnaitė K, Gauronskaitė R, Šlekytė G, Danila E, Zablockis R. Evaluation of obstructive sleep apnea phenotypes treatment effectiveness. Medicina (Kaunas). 2021;57(4):335.

8.     Ravindranath M, Sowjanya DS. Prevalence of hypothyroidism among patients with obstructive sleep apnea: A study in a tertiary care center. IP Indian J Immunol Resp Med. 2021;6(3):161–4.

9.     Sharma R, Sharma BB, Sharma R, Jain R, Mathur S. Obesity, thyroid and OSA: an intriguing triangle. J Assoc Physicians India. 2022;70(4):11-2.

10.   Thavaraputta S, Dennis JA, Laoveeravat P, Nugent K, Rivas AM. Hypothyroidism and its association with sleep apnea among adults in the United States: NHANES 2007-2008. J Clin Endocrinol Metab. 2019;104(11):4990-7.

11.   Pancholi C, Chaudhary SC, Gupta KK, Sawlani KK, Verma SK, Singh A, Verma AK, Usman K, Atam V. Obstructive sleep apnea in hypothyroidism. Ann Afr Med. 2022 Oct-Dec;21(4):403-409. doi: 10.4103/aam.aam_134_21. PMID: 36412342; PMCID: PMC9850883.

12.   Gencer A, Atahan E, Kadioglu P, Mutlu B. Investigation of the frequency of obstructive sleep apnoea syndrome in patients with subclinical hypothyroidism. ERJ Open Res. 2022 Oct 24;8(4):00186-2022. doi: 10.1183/23120541.00186-2022. PMID: 36299364; PMCID: PMC9589324.

13.   Zhao M, Huang X, Zheng H, Cai Y, Han W, Wang Y and Chen R (2024) Association between hypothyroidism and obstructive sleep apnea: a bidirectional Mendelian randomization study combined with the geo database. Front. Neurol. 15:1420391. doi: 10.3389/fneur.2024.1420391

14.   Fucà E, Costanzo F, Galassi P, Celestini L, Villani A, Valentini D, Vicari S. Emotional and behavioral features associated with subclinical hypothyroidism in children and adolescents with Down syndrome. Front Psychol. 2024 Feb 6;14:1294908. doi: 10.3389/fpsyg.2023.1294908. PMID: 38379845; PMCID: PMC10878309.

15.   Alreshidi NF, Alenzi H, Alrashidi R, Aljaloud LZ, Alshammari AB. The Relationship Between Thyroid Dysfunction and Sleep Quality Among Population of Saudi Arabia. Int J Gen Med. 2024 May 29;17:2497-2505. doi: 10.2147/IJGM.S462512. PMID: 38831928; PMCID: PMC11144793.

16.   Zhai L, Gao X. Recent advances in the study of the correlation between obstructive sleep apnea and thyroid-disorders. Sleep Breath. 2025 May 5;29(2):176. doi: 10.1007/s11325-025-03350-y. PMID: 40323542.

17.   Benjafield AV, Ayas NT, Eastwood PR, Heinzer R, Ip MSM, Morrell MJ, et al. Estimation of the global prevalence and burden of obstructive sleep apnea: a literature-based analysis. Lancet Respir Med. 2019;7(8):687-98.

18.   Kujovic M, et al. Treatment of hypertension and obstructive sleep apnea counteracts cognitive decline in common neurocognitive disorders in diagnosis-related patterns. Sci Rep. 2023;13:7556.

19.   Labarca G, Gower J, Lamperti L, Dreyse J, Jorquera J. Chronic intermittent hypoxia in obstructive sleep apnea: a narrative review from pathophysiological pathways to a precision clinical approach. Sleep Breath. 2020;24(3):751-60.

20.   Liu PY, Reddy RT. Sleep, testosterone and cortisol balance, and ageing men. Rev Endocr Metab Disord. 2022;23(6):1323-39.