A narrative review on obstructive sleep apnea in China: A sleeping giant in disease pathology

Yuxi Wei; Yu Liu; Najib Ayas; Ismail Laher

doi:10.4103/hm.hm_49_22

REVIEW ARTICLE

Year : 2022 | Volume : 6 | Issue : 4 | Page : 232-241

A narrative review on obstructive sleep apnea in China: A sleeping giant in disease pathology

Yuxi Wei¹, Yu Liu², Najib Ayas³, Ismail Laher¹
¹ Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
² Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Department of Pharmacology, Shanxi Medical University, Taiyuan, China
³ Divisions of Critical Care and Respiratory Medicine, The University of British Columbia; Sleep Disorders Program, University of British Columbia Hospital, Vancouver, British Columbia; Canadian Sleep and Circadian Network, Montreal, Quebec, Canada

Date of Submission	12-Oct-2022
Date of Acceptance	22-Nov-2022
Date of Web Publication	16-Dec-2022

Correspondence Address:
Prof. Ismail Laher
Department of Anesthesiology, Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3
Canada

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/hm.hm_49_22

Abstract

We review the aspects of obstructive sleep apnea (OSA), which is the most common respiratory disorder of sleep in China. Approximately 176 million people in China have apnea/hypopnea index ≥5/h, ranking first among the ten countries with the highest prevalence rates. Two-thirds of patients do not receive treatment at all or withdraw after only brief treatment in a survey nested in two centers in China. Drowsiness and progressive cognitive impairment related to OSA decrease work performance and add to workplace errors and accidents. Many patients with OSA remain undiagnosed. Untreated OSA increases the risk of developing cardiovascular diseases and metabolic diseases. Undiagnosed and untreated OSA patients place a great burden on healthcare costs and services, and thus enormous economic burdens across most countries across the world, due to the global epidemic of obesity, an important contributor to OSA. Continuous positive airway pressure is the first-line treatment for OSA in China; however, adherence levels are poor. Effective and less labor-intensive methods that improve adherence need to be further investigated. Traditional Chinese medicine and acupuncture are promising treatments but with unproven efficacy.

Keywords: Acupuncture, cognitive impairment, continuous positive airway pressure treatment, economic burden, obstructive sleep apnea

How to cite this article:
Wei Y, Liu Y, Ayas N, Laher I. A narrative review on obstructive sleep apnea in China: A sleeping giant in disease pathology. Heart Mind 2022;6:232-41

How to cite this URL:
Wei Y, Liu Y, Ayas N, Laher I. A narrative review on obstructive sleep apnea in China: A sleeping giant in disease pathology. Heart Mind [serial online] 2022 [cited 2023 May 31];6:232-41. Available from: http://www.heartmindjournal.org/text.asp?2022/6/4/232/363952

Introduction

Obstructive sleep apnea (OSA), the most common respiratory disorder of sleep, is characterized by repetitive collapse of the upper airway during sleep due to the loss of tone in muscles supporting soft tissues in the throat such as the tongue and soft palate.^[1] Relaxed soft tissues partially or completely block airflow, causing snoring, periodic cessation of breathing, gasping, and arousal from sleep. Current guidelines for OSA diagnosis in China follow traditional international standards that use the apnea-hypopnea index (AHI) to define severity, where the total number of breathing cessations (apneas) and partial loss of breath for ten seconds or more (hypopneas) per hour of sleep are used to determine the AHI of patients [Table 1].^[2] Patients either with AHI ≥5 (accompanied by at least one symptom including snoring, insomnia, witnessed apneas, gasping, daytime sleepiness, and fatigue) or with AHI ≥15 are diagnosed with OSA.

Table 1: Apnea-hypopnea index for diagnosis and classification of obstructive sleep apnea

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Using the American Academy of Sleep Medicine 2012 diagnostic criteria and AHI threshold values, it is estimated that about 936 million adults aged 30–69 have OSA globally.^[3] The prevalence of OSA in Chinese adults is about 176 million, ranking first among the top ten countries with reliable prevalence data for OSA.^[3] The prevalence of OSA among middle-aged Chinese is approximately 12.6% based on the 1.398 billion population of China in 2019, which exceeds the prevalence of OSA in Hong Kong, China, estimated at the beginning of the second millennium^[4],[5] and can be partially explained by increases in obesity due to poor lifestyles, incoming growth, and dietary changes.

Obesity, especially central obesity, is a major risk factor for OSA. Approximately 40% of obese patients have OSA, and about 70% of patients with OSA are obese.^[6],[7] In China, the overall prevalence of central obesity was reported as 29.1% (28.6% in men and 29.6% in women) based on a study of nearly half a million participants published in 2019.^[8] Obesity affects the respiratory system directly by mechanical changes due to fat deposition that narrows the upper airway and predisposes it to collapse. Structural changes in the thoracic-abdominal area restrict diaphragmatic mobility and rib movement, which promotes changes in the dynamics of the respiratory system and reduces its compliance, leading to mechanical impairment of respiratory muscles.^[9] People with a higher body mass index (BMI) accumulate a larger percentage of fat in their tongues where fat mostly accumulates towards the back of the tongue [Figure 1]. Interestingly, increased tongue volume and deposition of fat at the base of the tongue occur more commonly in obese apneic patients compared to obese controls.^[10] A 10% weight gain is predicted to lead to an approximately 32% increase in the AHI and a six-fold risk of developing moderate-to-severe sleep-disordered breathing.^[11] Weight loss generally improves OSA severity, with a 10% weight loss predicted to decrease AHI by about 26% according to a 12-year prospective cohort study.^[11] In addition, reducing excess fat, in general, can reduce the size of the tongue. For example, the reduced tongue size observed in magnetic resonance imaging of obese patients with a 10% weight loss is considered the primary reason for improved AHI scores.^[12] Nevertheless, reducing weight is not easily achievable in many patients and OSA may not always be resolved by weight loss alone. Furthermore, Chinese people are more susceptible to OSA even with a lower BMI compared with Caucasians, likely because of smaller and more restrictive facial structures.^[13] A recent study calculated BMI cutoff values in different race-ethnicities future risk of diabetes as compared to the European populations and reported cutoff values of 26.9 kg/m² and 22.2 kg/m² in the Chinese populations, which is at par with 30 kg/m² for obesity and 25 kg/m² for overweight in the European populations.^[14] These evidence suggests that at similar BMI values, Chinese people may suffer more frequent and more severe pauses of breathing during sleep. However, the presence of normal-weight in metabolically obese phenotype means that, BMI is not an accurate predictor of central obesity. Several studies report that waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHTR) are associated with all-cause cardiovascular disease, independently of BMI. However, no study has focused on the relationship between these anthropometric indicators and OSA in normal-weight populations. It would be of interest to investigate the prevalence of OSA among metabolically healthy and unhealthy phenotypes in normal-weight populations and obese populations, respectively.^{[15],[16],[17],[18]} Other risk factors for OSA include male gender,^[19] increased age,^[20] upper airway and craniofacial abnormalities,^[21] family history/genetics,^[22],[23] low levels of thyroid hormone,^[24],[25] acromegaly,^[26] smoking,^[27] and use of sedatives (including alcohol) and muscle relaxants.^[28] The predominant central fat deposition pattern around the neck, trunk, and abdominal viscera in men compared with women contributes to increased risk of OSA in males, which highlights the association between WC, WHR, WHTR, and OSA, rather than the decisive impact of BMI.^{[29],[30],[31]}

Figure 1: Normal upper airway and blocked upper airway in obese

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The Economic and Public Health Burden of Sleep Apnea

The economic costs associated with OSA are substantial for both the individual and for society as a whole [Table 2]; these economic costs are very likely to be underestimated given that the disease remains undiagnosed in an alarmingly large percentage of afflicted individuals.^[32] Undiagnosed and untreated OSA adds an increased strain on the health care system and increases direct and indirect costs associated with the condition. OSA has short- and long-term impacts, including memory loss, reduced learning, innovation, and decision-making capacity, and a higher risk of developing Alzheimer's disease (AD) and dementia, which in turn further burdens patients and their families and adds to public health systems. Other well-described consequences of OSA include work limitations and absenteeism, occupational injuries, and motor vehicle crashes.

Table 2: Economic costs of obstructive sleep apnea

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The economic burden of obstructive sleep apnea

Although it is difficult to accurately quantify the economic burden of OSA, it is undoubtedly large and continues to grow. It was estimated that more than 800,000 drivers were involved in OSA-related motor-vehicle collisions in the United States (US) alone, costing approximately 15.9 billion dollars annually in 2000.^[33] The cost of OSA-related motor vehicle accidents climbed to 32.4 billion in the US in 2015.^[34] In China, the financial burden that diagnostic and therapeutic strategies must be paid out-of-pocket or through an employer-sponsored health plan is one reason for the high undiagnosed rates. The New England Comparative Effectiveness Public Advisory Council presented a cost-effectiveness analysis on diagnostic testing in a hypothetical cohort of 1,000 Medicaid patients and reported the following cost analysis: Morphometric + polysomnography (PSG), $674,621; PSG alone, $652,830; Berlin questionnaire + PSG, $518,066; and Type III home sleep testing (HST) alone, $200,700.^[35] HST as an alternative to PSG is restricted to patients with a high pretest likelihood of moderate-to-severe OSA due to underestimated AHI.^[36],[37] Both phenotype errors of falsely negative results and category errors of moderate-to-severe moving to mild-to-moderate OSA are present because of the use of total recording time rather than total sleep time as the denominator when calculating AHI in HST.^[38] HST is not an over-the-counter test in China, whereas no data reporting the percentage of use HST and PSG in the diagnosis of OSA are available.

Undiagnosed OSA has a significant economic burden on society: The yearly cost of treating undiagnosed OSA patients is $1,950 to $3,899 higher than in non-OSA patients, while OSA patients that are treated with continuous positive airway pressure (CPAP) cost $2,700 to $5,200 less per year than OSA patients not receiving treatment based on 106 studies.^[39] Currently, there is not a definitive undiagnosed rate of OSA in China, yet 80% of patients who had not been previously diagnosed with OSA were found to be at high risk of OSA in the preoperative screening for OSA surgery.^[40],[41] Moreover, treatment choices by patients with OSA in China are not well accepted. In a survey nested in two prospective cohort studies of OSA in China, nearly two-thirds of subjects chose not to receive treatment even after OSA diagnosis, and nearly half of the patients had negative views on treatments for OSA.^[42] Untreated OSA leads to an increased risk of developing complications such as cardiovascular diseases (e.g., hypertension, heart failure, and stroke), metabolic diseases (e.g., type 2 diabetes, nonalcoholic fatty liver disease, and nonalcoholic steatohepatitis), etc.^{[43],[44],[45],[46]} Therefore, it is not a surprise that untreated OSA patients have increased health care utilization and costs across all points of service compared to matched control patients.^[47]

The public health burden of obstructive sleep apnea

OSA-induced cognitive impairments make it difficult for people to participate fully in the workforce; indeed, workers with OSA have increased work absences and decreased performance while at work as manifested by decreased productivity and increased workplace errors or occupational accidents.^[50] The odds of workers with self-reported OSA being involved in occupational accidents were 2.18 times greater than in controls, and the risk remained higher (Odds ratio [OR]: 1.78) even after studies without PSG tests were excluded.^[39]

Memory

Memory consolidation takes place in four stages of the sleep cycle and facilitates preserving key information and discarding other information.^[51] During the nonrapid eye movement (NREM) stages, important memories are filtered out and become more concrete. This process continues during the rapid eye movement (REM) stage so that the reinforced information can be recalled when needed. NREM sleep has been linked with declarative memory formation, such as basic facts and statistics. REM sleep is believed to boost procedural memory and process emotional memories such as remembering a sequence of steps and coping with difficult experiences. Sleep deprivation affects memory consolidation since the brain does not have sufficient time to strengthen neural connections and create new pathways for new information.^[52],[53] One night of CPAP failed to alter sleep-dependent procedural memory consolidation, whereas a 3-month CPAP treatment with a mean adherence of more than 5 h restored declarative memory deficit in OSA patients.^[54],[55] Several factors including OSA severity, the course of disease, treatment duration, and treatment compliance contribute to the reversibility of OSA-related memory consolidation deficits. Studies with more specific inclusion and exclusion criteria are needed to fully elucidate whether the memory impairments are reversible.

It is not surprising to find patients with OSA have lower semantic autobiographical memory that pertains to personal facts, traits, or general self-knowledge,^[56],[57] since OSA causes sleep fragmentation that interferes with the sleep cycle. Interestingly, contrary to episodic memory impairments reported in previous studies, episodic autobiographical memory typically associated with the time and place of events was preserved in the OSA group in a recent age-matched study.^[58] In addition, poor semantic recall from early adult life in this study was significantly correlated with more depressive symptoms (P = 0.006).^[58] OSA has long been linked to chronic depression where patients also have difficulty in autobiographical memory collection.^[59],[60] More studies are needed to explore whether OSA causes depression and memory impairment, or whether OSA and depression independently contribute to impaired memory consolidation. Moreover, people who are sleep deprived are at risk of incorporating misleading post-event information into memory retrieval.^[61] Even if getting sufficient total hours of sleep, fragmented sleep also negatively affects memory consolidation.^[62]

Decision-making

In addition to impairing basic cognitive functions, an inadequate amount of sleep also affects high-order cognitive processes in decision-making. There is an increased propensity to make risky decisions after total sleep deprivation.^[63] Further, total sleep deprivation is particularly problematic for decision-making involving uncertainty and unexpected changes as indicated by diminished skin conductance responses followed by an unannounced reversal of contingencies.^[64] “Feedback blunting” arising from sleep deprivation underlies failures to adapt to uncertainty and changing contingencies.^[51] Recent studies indicate that prolonged sleep restriction, or partial sleep deprivation, is more detrimental than total sleep deprivation, and inter-individual differences are substantial in the effects of sleep loss.^[65]

The association between sleep disturbance and executive functioning was reviewed in a previous study, where sleep disturbance was used as an umbrella term encompassing total and partial sleep deprivation, and sleep fragmentation.^[66] Executive functioning may have an important role in decision-making under risk.^[67] In addition to sleep fragmentation and sleep deprivation, intermittent hypoxia (IH) also contributes to deficits in executive functioning in patients with OSA.^[68] It is assumed that IH disturbs prefrontal lobe function thus leading to executive dysfunction.^[69] Acute hypoxia exposure with the fraction of inspired oxygen (FiO₂) = 13% deteriorates executive functions, while the postexposure deterioration is not proportional to the hypoxic stages of FiO₂ 13%, 12%, and 11%.^[70] Interestingly, mild hypoxic exposure also enhances cerebral blood flow, neurogenesis, and brain vascularization, suggesting that appropriate dosage and exposure time may facilitate improved cognitive function.^[71],[72] In addition, intermittent hypoxic-hyperoxic training improves cognitive parameters in elderly patients with cognitive impairment.^[73],[74]

Learning and creativity

Connecting loosely associated ideas is a hallmark of creativity, and this ability is strengthened by healthy sleep habits.^[75] Better sleep quality, longer duration, and greater consistency are associated with better academic performance in college students and account for 25% of the variance in academic performance.^[76] NREM sleep provides an opportunity for the restructuring and reorganization of information in the brain, and new ideas and connections between thoughts often emerge during REM sleep.^[77] In a study of cognitive flexibility, subjects woken up during REM sleep could solve 32% more anagram puzzles compared with themselves when woken up during NREM sleep, while performance following REM sleep awakenings was equal to that seen in the wake sessions.^[78] Solving anagram puzzles requires strong creative thinking and problem-solving skills. Therefore, REM sleep could play an important role in innovation and creative problem-solving. In addition, the hippocampus is critical in the formation, organization, and storage of new memories. Pre- or post-training sleep-deprived mice exhibited memory impairment in hippocampus-dependent versions of Morris water maze, fear-conditioning, and T-maze tests.^[79],[80] Further, performance in hippocampus-dependent spatial tasks was impaired after decreased REM sleep.^[81] Nevertheless, the importance of NREM sleep cannot be underestimated: Slow-wave sleep perturbation markedly attenuated neuroplasticity restoration, thus reducing learning efficiency in humans.^[82]

Motor vehicle accidents

Drowsiness while driving is a major contributor to motor accidents. According to the National Highway Traffic Safety Administration of the US, drowsiness while driving led to over 91,000 motor vehicle accidents, resulting in roughly 50,000 injuries and 800 deaths in 2017. In China, 414 out of 787 traffic accidents that occurred in the Huai'an section of the Beijing Shanghai Expressway were caused by drowsiness while driving, accounting for 52.6% of the total number of accidents.^[83] However, these data underestimate the impact of drowsiness while driving because it is often impossible to accurately determine whether drowsiness while driving causes an accident, especially after fatal crashes. To evaluate the association of driver sleepiness with the risk of car crashes, a population-based case-control study conducted in Shenyang, China, reported a strong association between chronic sleepiness identified by the Epworth Sleepiness Scale (ESS) and the risk of car crashes with an odds ratio of 2.07 among drivers who identified themselves as sleepy (ESS ≥10).^[84] The link between sleepiness at the wheel and the risk of motor vehicle accidents was further assessed in a systematic review comprising 17 eligible studies of more than 70,000 participants.^[85] A dose-dependent relationship between acute sleep deprivation 24 h before a motor vehicle accident and culpable involvement in the accident in the US was reported.^[86] Drivers who reported having 6, 5, 4, and <4 h of sleep 24 h before the crash were 1.3, 1.9, 2.9, and 15.1 times of odds of being culpable for the crash [Figure 2].^[73]

Figure 2: Odds ratios for driver culpability in relation to total hours of sleep 24 h before vehicle accidents. Sleep 7–10 h is a reference. Odds ratios in drivers who reported having sleep for 6–7 h, 5–6 h, 4–5 h, <4 h, and >10h are 1.3 (95% confidence interval [CI], 1.04–1.7), 1.9 (95% CI, 1.1–3.2), 2.9 (95% CI, 1.4–6.2), 15.1 (95% CI, 4.2–54.4), and 1.3 (95% CI, 0.9–1.7), respectively. Based on data from Tefft BC (2018): Acute sleep deprivation and culpable motor vehicle crash involvement. Sleep 41 (10). DOI: 10.1093/sleep/zsy144.^[73]

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Young drivers (18–24 years) are over-represented in sleep-related motor vehicle accidents, accounting for one-fifth of fatal crashes in developed countries. Compared with older adults, young drivers are more susceptible to sleep deprivation.^{[87],[88],[89]} Specific characteristics such as immature decision-making areas in the brain,^[90],[91] slower reaction time while sleepy,^[92],[93] and a lower sleep loss tolerance in young drivers may provide clues for this disparity.^[94] However, most studies on the prevalence of OSA in China focused on adults, and screened hospitalized patients and local area residents.^{[3],[95],[96]} The limited number of studies on the consequences of sleep loss on young drivers' performance suggests that standard deviation of lateral position and lane crossings are two common predisposing factors.^[97] Compared with age-matched people who slept more than 6 h, young drivers with an average amount of sleep of 6 or fewer hours were at an increased risk for motor vehicle accidents (relative risk [RR], 1.21) in a 2-year follow-up study.^[98]

Objective tools such as multiple sleep latency test are effective in sleep quality diagnosing, whereas self-reported scales are more economic and convenient. The Sleep Quality Scale (SQS) developed in South Korea is one of the most popular self-evaluation SQSs. Chen et al. adapted it to Chinese culture and the driving environment in China.^[83] Low-to-moderate correlations were found between the Chinese version of SQS and Daytime Sleepiness Perception Scale version 4 and Dangerous Driving Behavior Scale, indicating the validity of the revised scale.^[83]

Long-term impacts

Sleep plays a crucial role in learning and memory consolidation throughout life, so it is not surprising that sleep disorders are associated with the emergence of cognitive deficits.^[99] Disturbed sleep quality, quantity, and sleep-wake rhythm occur frequently in older adults with cognitive impairment, and there is growing support for the bidirectional relationship between sleep disturbance and cognitive impairment.^[100] OSA, one of the most common sleep disorders, has been linked with cognitive problems involving attention, thinking, memory, and communication.^[101] A population-based 5-year follow-up study showed that people with sleep apnea have a higher risk of developing dementia.^[102] A meta-analysis of 27 observational studies further confirmed the association between sleep and cognitive impairment or AD.^[103] Older women with lower sleep efficiency and longer sleep latencies have 1.5 and 1.4 higher odds of developing mild cognitive impairment (MCI), considered a stage between mental decline with normal aging and the onset of dementia within 5 years.^[104] Further, sleep has a role in the removal of detrimental substances. The accumulation of amyloid beta, a hallmark of AD, increases even after one night of sleep deprivation.^[105] The deposition of amyloid beta in the brain is associated with reduced and fragmented slow-wave sleep.^[106] Artificially improving slow-wave sleep by use of a transcranial current oscillating at a low frequency in older adults enhanced their performances on memory tests, compared with those in the sham control group.^[107] There is limited evidence to support the view that good sleeping habits can delay the onset of AD and dementia, which has encouraged the use of sleep medications as means of breaking the link between sleep disturbance and AD.^[108] Additional large-scale studies are needed to determine fundamental questions such as the clearance and deposition rates of beta-amyloid as a function of sleep times in males and females of various ages and the effects of various treatments for OSA on the accumulation of beta-amyloid.

Current Treatment Strategies

CPAP is considered the first-line treatment for moderate- to-severe OSA. CPAP prevents the collapse of the upper airway by establishing a positive pressure in the pharynx during sleep. It is effective in eliminating sleep fragmentation and maintaining nocturnal oxygenation, thereby improving daytime sleepiness, quality of life, and neurocognitive function. Adequate CPAP mitigates OSA-related risk for mortality in Chinese patients.^[109],[110] A study focusing on patients' attitudes toward treatments in China reported that only 10.25% of OSA patients received CPAP.^[31] Nearly two-thirds of the subjects received no treatment, and 53.4% of them believed that treatment was not necessary despite 53.7% of them being diagnosed with severe OSA.^[31] In addition, compliance with CPAP is of concern. The type of CPAP masks may affect compliance: Claustrophobic patients are advised to choose nasal pillow CPAP, nasal CPAP is suitable to patients who move a lot during sleep, and full-face CPAP is recommended for patients who breath through the mouth. By accessing the adherence to CPAP among a group of OSA patients in Tianjin, China, only half of the subjects remained adherent to CPAP, whereas the other half either never initiated the treatment after titration or abandoned the treatment after a short period of use.^[111] Low adherence has also been reported in Hong Kong, China.^[112] Beijing Anzhen Hospital, Capital Medical University investigated the factors that determined compliance with CPAP treatment and reported that there were no significant differences in age, sex distribution, BMI, complications, and sleep-related symptoms between the good and poor compliance groups in 2019. Better acceptance was observed in patients with higher AHI, fewer hypopnea events, and higher arousal threshold, which is consistent with the previous conclusion that AHI is a significant determinant of CPAP adherence.^[113]

A CPAP titration study may be performed to determine the best pressure settings to improve sleep quality. Making the titration trial a comfortable first CPAP experience improves compliance. Patients may experience a sore or dry throat and facial irritation after the initial CPAP titration study, indicating that the mask type used may not be suitable. The tendency to not wear a CPAP mask or remove it (consciously or unconsciously) when sleeping results in inadequate treatment. A single, brief mask fitting session increased compliance (>4 h in 70% of nights) in suboptimal CPAP adherence patients from 13.3% to 60%.^[114] However, in China as in other countries, data on voluntary return for mask changing and physician-requested changing during follow-up are not recorded, and studies on mask types, mask changes, and compliance are lacking.

Early interventions are critical since patients are more likely to accept CPAP usage when introduced soon after diagnosis of OSA.^[115],[116] It is important to educate patients and encourage them to contact healthcare providers to schedule another CPAP titration if they experience choking, gasping, and repeated arousals during sleep. A higher CPAP pressure is needed to keep airways open if symptoms occur, otherwise patients may deem the CPAP treatment ineffective and so abandon treatment. Intensive support such as patient education (including that of the patient's partner), phone coaching sessions, additional CPAP titrations, and home visits by sleep nurses improves CPAP adherence.^{[117],[118],[119]} Cognitive behavioral therapy and motivational enhancement to improve confidence in the treatment and establish a collaborative style of interaction are also effective.^{[55],[120],[121]} However, these interventions are labor intensive. The use of short educational videos as a simpler and low-cost tool has been widely discussed. However, results regarding rates of return to a sleep clinic and CPAP adherence are inconsistent from studies using this approach.^{[122],[123],[124]} In addition, group CPAP education which is also less labor-intensive and time-consuming may be an alternative to individual CPAP counselling. The benefits of group educational strategies have been demonstrated in managing patients with diabetes and rheumatoid arthritis.^[125] However, further prospective randomized studies are required, despite improved adherence to CPAP reported in a retrospective study.^[126] Validated questionnaires such as SURE (Sure of myself; understand information; risk-benefit ratio; and encouragement) and CollaboRATE can be useful tools for healthcare personnel to evaluate decisional conflicts and shared decision-making from the patient's perspective.^[127] Patients with low decisional conflict and high shared decision-making are more adherent to CPAP.^[116] Further studies are needed to demonstrate whether using questionnaire tools before CPAP initiation can improve adherence.

The benefits of CPAP on cognitive deficits are still unclear. One night of CPAP use was reported to augment attention and vigilance.^[54] Improved vigilance and attention also manifested in driving performance.^[128] Three-month therapy with CPAP led to a resolution of declarative memory deficits in OSA patients in proportion to the increase in NREM sleep.^[53] However, whether CPAP delays the trajectory of cognitive decline and dementia in patients with MCI is unclear due to differences in the study design, the number of patients, heterogeneous OSA definition, etc.^{[129],[130],[131],[132]} Further, in a meta-analysis of randomized control trials published from 1971 to 2014, only vigilance was improved by CPAP compared with others such as sham CPAP, oral placebo, untreated, and conservative treatment.^[133] No significant benefits were observed in attention, working memory, processing speed, memory, verbal fluency and visuoconstructive skills.^[123] Rigorous randomized control trials are needed to determine the effects of CPAP on various markers of cognitive deficits.

Non-CPAP therapies such as oral appliance therapy and upper airway surgery used to treat patients unable to tolerate CPAP also achieve positive results in many cases, but their therapeutic efficacy is unstable.^[134],[135] A growing body of evidence indicates that traditional Chinese medicine (TCM) improves the symptoms, biochemical parameters and quality of life in OSA patients.^[136],[137] Acupuncture, which involves inserting needles into the skin and stimulating sensory nerves and has roots in TCM, relieves chronic pain and improves other physical conditions.^{[138],[139],[140],[141],[142]} Studies have reported that acupuncture effectively decreases AHI, respiratory events, and ESS scores in patients with mild and moderate OSA.^[143],[144] A single session of either manual acupuncture or electro-acupuncture has an acute effect in reducing the AHI as well as the number of respiratory events in patients with moderate OSA.^[145] Systematic reviews and meta-analyses of randomized controlled trials (RCTs) reported the strengths of acupuncture in improving AHI and mean oxygen saturation (SaO₂) compared to no treatment or CPAP treatment in OSA of different severities.^[146],[147] Acupuncture could be an alternative for patients burdened by the high cost or significant inconvenience of CPAP treatment. However, additional data are needed to verify the efficacy of acupuncture. A randomized, placebo-controlled, pilot study of the efficacy of acupuncture in OSA was published in 2007,^[131] whereas the use of CPAP for the treatment of OSA was introduced by Sullivan and his colleagues in 1981. Hundreds of RCTs on CPAP are cited in OSA reviews, but the number of RCTs in reviews on acupuncture is in the single digits.^{[134],[135],[148]}

Sleep apnea falls in the category of snoring and drowsiness in ancient Chinese medical literature. It is considered to be caused by spleen deficiency and lung Qi impairment in TCM. Phlegm accumulates, and Qi stagnates in the spleen and cannot be conveyed to the lungs. Lianquan located in the throat is the most commonly used acupoint to comfort the tongue and airway smooth muscles.^[149] Other acupoints including Fenglong, Zusanli, Sanyinjiao, Gongsun and Yinlingquan selected from the stomach and spleen meridian help to transport and dispel phlegm dampness, stimulate airway muscles and stimulate Qi circulation.^[137] Few resources have been allocated to investigating the biologic mechanism of acupuncture in OSA treatment. It is accepted that acupuncture stimulates and strengthens tissues and muscles of the upper airways, so they have less chance to collapse during episodes of sleep. Recently, the Beijing University of Chinese Medicine drafted a protocol to explore the efficacy and mechanisms of electro-acupuncture where the cognitive and emotional status will be evaluated, and neuroimaging scans will be performed to assess changes in neuroplasticity.^[150] Interestingly, acupuncture did not reduce AHI, daytime or nocturnal blood pressure, or the quality of life in hypertensive patients with OSA.^[151] Additional studies are needed to better understand the biologic mechanisms of TCM and to determine which OSA patients will benefit from acupuncture.

Future Directions

Undiagnosed and untreated OSA adds a huge burden on the healthcare system at a large and ongoing economic cost. However, there is a lack of data on economic burdens of OSA in China, and no linked database is available. Joint efforts of the healthcare system, transportation system, workplace, patients, and researchers are required to fully appreciate the economic burden of OSA in China. This brief review discusses the personal and societal impact of OSA and reviews patient awareness and self-screening, the current main treatments for OSA in China, and patient attitudes to the treatments available.

Motor accidents often result from cognitive impairment in patients with sleep apnea, mainly manifested as decreased reaction response times. Efforts should be made to improve SQSs more suitable to the Chinese culture to identify those who are likely to be drowsy while driving or operating heavy machinery. Valid scales could be an indicator and facilitate the screening of OSA. Further, the prevalence of OSA among young people in China is a research direction worth exploring, as young people are more sensitive to the harms of sleep deprivation.

Finding less labor-intensive and time-consuming methods to improve CPAP treatment adherence is also a priority. From the perspective of health care providers, a standard operating procedure is required to make titration trials a comfortable first CPAP experience. Using validated questionnaires that focus on decisional conflicts and shared decision-making of patients could improve CPAP adherence. Further, large-scale, rigorous RCTs are needed to elucidate the impacts of CPAP on cognitive impairment. High-quality systematic reviews and meta-analyses based on the veracity of recent findings are also needed.

The application of acupuncture in OSA rooted in spleen function and Qi stagnation in TCM may reduce AHI, respiratory events, and improve SaO₂, although the biologic mechanisms and the efficacy in populations with comorbidities remain to be confirmed. Other TCM approaches show benefits in reducing inflammation, oxidative stress, and snoring, but the safety and efficacy of long-term use need further study.

Ethical statement

The ethical statement is not applicable for this article.

Financial support and sponsorship

Nil.

Conflicts of interest

Dr. Ismail Laher is an Editorial Board Member of Heart and Mind. The article was subject to the journal's standard procedures, with peer review handled independently of Dr. Ismail Laher and their research groups. There are no conflicts of interest.

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