EDITORIAL article

Front. Neurol.
Sec. Sleep Disorders
doi: 10.3389/fneur.2022.961240

Editorial: Clinical Aspects of Obstructive Sleep Apnea and Cardiovascular Consequences: a clinical review and summary of research topic

 Kittisak Sawanyawisuth1*, Shazia M. Jamil2 and  Melissa Lipford3
  • 1Faculty of Medicine, Khon Kaen University,, Thailand
  • 2Scripps Clinic, United States
  • 3Mayo Clinic, United States
Provisionally accepted:
The final, formatted version of the article will be published soon.

OSA is a common disease in clinical practice and is often undiagnosed. In the general population, the prevalence of OSA can be as high as 38% (1), however sharply inclines to up to 78 to 90% in elderly women and men, respectively (1). A population study in Australia noted a high prevalence in middle-age men and women (57.7% and 41.7%, respectively) (2).For those admitted with cardiovascular disease or patients with cerebrovascular disease, the prevalence of OSA in both conditions was also high at 48% and 70.4% (3,4).There are several risk factors of OSA which can be classified into four categories: body mass index, age and sex, anatomical risks, and co-morbid diseases. First, obesity is a well-known risk factor for OSA. Approximately 45% of obese patients were found to have OSA (5), and the prevalence was higher in those undergoing bariatric surgery at 77.2% (6). In contrast, 60% of patients with OSA were obese in Western countries (7), while only 36.6% of patients with OSA in the Eastern countries were obese (8). Note that criterion to define obesity is different (30 vs 25 kg/m 2 ) in different populations. Secondly, older age, male sex and post-menopausal women are all risk factors for OSA. The prevalence of OSA increases from 10% to 17% in male patients as age group increases from 30-49 years to 50-70 years with an apnea-hypopnea index (AHI) of 15 events/hour or more (9). In adult patients, male:female ratio appears to be 4.9:1 (10), however narrows to 1:1 in post-menopausal women (11). Thirdly, craniofacial abnormalities that lead to narrow oropharyngeal space such as torus palatinus, torus mandibularis, macroglossia, tonsillar enlargement, microretrognathia, or edentate status are risk factors (12,13). Finally, certain co-morbid diseases may be related to OSA such as hypothyroidism, chronic kidney disease, HIV infection, epilepsy, asthma, chronic obstructive airway disease, acromegaly, and allergic rhinitis (14)(15)(16)(17).Diagnosis of OSA can be made by several devices. The gold standard is polysomnography type 1 with evidence of AHI or respiratory disturbance index (RDI) of five or more events/hour. Other types of polysomnography such as type 2 and 3 are also acceptable as they have sensitivity and specificity of 80% or over. A study from China found that home sleep test had comparable AHI (p = 0.103) with good correlation with in-lab polysomnography (r 0.779; p < 0.001), and sensitivity, specificity, and accuracy of 94.9%, 62.5% and 91.0%, respectively (18). Other home-based testing devices such as smart watch or arterial tonometry are also reported to be reliable in diagnosing OSA with sensitivity of 90.64% and 95.8%, respectively (19,20). Note that out of center devices may only be reliable in those with moderate to severe OSA.The mainstay treatment of OSA is a continuous positive airway pressure device (CPAP). There is significant evidence suggesting that CPAP is effective in reducing cardiovascular risk. For hypertension, CPAP therapy reduced new onset hypertension by 29% (Hazard ratio of 0.71; 95% confidence interval 0.53, 0.94) (21). Systolic and diastolic blood pressure reduction was 2.6 and 2.0 mmHg, respectively with CPAP therapy (22). Blood pressure reduction with CPAP therapy was more pronounced in patients with resistant hypertension with OSA since systolic and diastolic blood pressure reduction was 7.21 and 4.99 mmHg respectively (23). CPAP therapy in patients with heart failure has shown reduced risk of heart failure in patients 60 years and older by 17-19% and increased left ventricular ejection fraction by 5.18 (95% confidence interval 3.27, 7.08) (24,25). In patients with concurrent OSA and atrial fibrillation, those using CPAP therapy had reduced risk of atrial fibrillation recurrence by 40% than nonusers (26,27). Additionally, CPAP therapy could be held responsible in converting atrial fibrillation to sinus rhythm in 2 cases (28,29). Patients with severe OSA were found to have lower incidence of fatal cardiovascular events when treated with CPAP than those without treatment (0.35 vs 1.06 per 100 person-year; p = 0.0008) (30). Note that the goal of CPAP therapy is to use it regularly and throughout the duration of sleep (i.e.7-8 hours per night), limiting interpretation of results of a large randomized controlled trial showing no cardiovascular benefits in a population using CPAP for an average of 3.3 hours/night (31,32).Even though CPAP is effective in treatment of OSA and its consequences, acceptance and compliance of CPAP is still problematic. Studies show that in resource limited countries, approximately half of patients with OSA agree to purchase CPAP and about half of them use CPAP regularly (33-35). An issue with insurance coverage may affect patient's decision on CPAP acceptance or purchasing. Other treatments include oral appliance, weight reduction in overweight and obese patients, positional therapy, and exercise (36)(37)(38).
OSA is a common disease with several medical consequences if left undiagnosed or untreated, which can be categorized into two groups: cardiovascular and non-cardiovascular.This research topic focused on clinical aspects of cardiovascular diseases including review, epidemiological, treatment-related, or interventional studies. Cardiovascular consequences of OSA included hypertension, coronary artery disease, cardiac arrhythmia, left ventricular hypertrophy, cardiac failure, and stroke (39-48).There are eight articles recently published in this topic with 41 authors from China, Germany, Japan, USA, Brazil, Israel, and Taiwan. These articles can be classified into three groups: review (1), epidemiological study (3), and CPAP-related (4).First, a review published by Yasir et al emphasized if cardiovascular outcomes in sleep-disordered breathing are under-estimated? The authors summarized how clinicians conducted research in the past and present to show cardiovascular outcomes in sleepdisordered breathing particularly in OSA. The authors proposed to have diagnostic approach by using personalized approach as well as big data research, and the need for identification of patients with OSA who are at risk for cardiovascular diseases.The three epidemiological studies published include a population-based study by Mayra dos Santos Silva, Markers of Carotid Plaque by Lavie, and correlation of cardinal features of OSA and blood pressure by Xia. The population-based study was conducted in older adults in Brazil. The authors found that severity of OSA was significantly related with cardiovascular consequences including hypertension and heart disease. The authors also found that obesity was not related to severity of OSA in older adults. Previous studies also showed that obesity may not be related to OSA diagnosis particularly in the elderly and those with hypertension (40,49). Xia et al conducted a retrospective study to show that both low oxygenation and arousal during apneic events in patients with OSA were significantly related to high diastolic blood pressure and hypertension. This article emphasized roles of intermittent hypoxemia during sleep and micro awakening from OSA to high blood pressure.Lavie et al showed that patients with OSA may already have carotid plaque destabilization even in asymptomatic patients. There were three important markers for carotid plaque abnormalities including 3-nitrotyrosine, intracellular lipids content, and smooth muscle cellactin. This study used an arterial tonometry device to diagnose OSA (50). labelled study in patients with OSA of moderate to severe degree. After one month of CPAP treatment, the left ventricular ejection fraction (LVEF) improved from 37.2% to 43.2%. Age and body mass index were independently associated with LVEF at the end of study with adjusted coefficients of -0.001 and 0.005, respectively. Their data indicated that an improvement in LVEF was likely to be observed in young patients with obesity. Even though the coefficients were quite small, this could be due to small sample size, necessitating need for studies with a larger sample size. Finally, Wang et al conducted a randomized controlled trial to evaluate the effect of drug-induced sleep endoscopy (DISE)-guided CPAP titration in comparison to physician guided CPAP pressure determination on subjective daytime sleepiness in patients with moderate to severe OSA. There were no significant differences in terms of CPAP pressure, residual AHI, compliance and daytime sleepiness between the two groups. They found that epiglottis (anterior-posterior collapse) was the independent factor for 95% of CPAP pressure. They concluded that both modalities are comparable in establishing optimal CPAP pressure to treat patients.In conclusion, OSA is frequently undiagnosed and is associated with cardiovascular risks. However, studies evaluating impact of treatment of sleep disordered breathing particularly OSA on cardiovascular risks have been limited, primarily due to poor adherence and small sample sizes. Future research needs are as follows: identification of OSA patients who are at high risk for developing cardiovascular diseases and randomized controlled trials evaluating long-term benefits of CPAP.

Keywords: Sleep Apnea, CPAP (continuous positive air pressure), Cardiovasclar diseases, Compliance, risk factor

Received: 04 Jun 2022; Accepted: 11 Aug 2022.

Copyright: © 2022 Sawanyawisuth, Jamil and Lipford. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Kittisak Sawanyawisuth, Faculty of Medicine, Khon Kaen University,, Khon Kaen, Thailand