Obstructive sleep apnea (OSA) is common in patients with type 2 diabetes, and the two are clinically, epidemiologically and pathogenetically relevant and independent of obesity. While the health risks of type 2 diabetes are now well recognized, the health risks of OSA and the medical burden it poses are still far from being understood. Therefore, efforts from various disciplines are needed to make people aware of the relationship between OSA and type 2 diabetes and to start taking practical actions.
To raise the level of awareness of the relationship between OSA and diabetes, the International Diabetes Federation Epidemiology and Prevention Group published a consensus on the issue in 2008, recommending that a global effort be made by all disciplines to bring about a full understanding of the link between OSA and type 2 diabetes, which has since been described in national journals. In order to further strengthen the cognitive concept of the relationship between OSA and type 2 diabetes and to improve the prevention and control of both diseases, experts from the Sleep and Respiratory Group of the Chinese Medical Association’s Respiratory Disease Branch and the Chinese Medical Association’s Diabetes Branch have carefully discussed this issue and reached a consensus on the relevant issues.
Introduction of OSA
OSA is mainly manifested as snoring with apnea and superficial breathing during sleep, recurrent hypoxemia, hypercapnia and sleep structure disorder at night, resulting in daytime sleepiness, cardiac, cerebral and pulmonary vascular complications and even multi-organ damage, which seriously affects the quality of life and life expectancy of patients.
Foreign data show that the prevalence of OSA among adults is 2% to 4%, and the epidemiological survey results of many provinces and cities in China show that the prevalence of OSA among adults is about 4%. Although the prevalence of obesity in China is not high, the prevalence of OSA is not low, which may be related to the characteristics of the national jaw and face structure. Research results show that OSA is an independent risk factor for many systemic diseases. However, there is a lack of awareness of the seriousness and prevalence of the disease among medical professionals, and there are also many problems in the clinical standard of care that need to be solved as soon as possible.
The consumption of health resources by OSA patients is twice as high as that of healthy people, therefore, proper assessment of OSA patients, correct diagnosis and timely treatment can reduce the consumption of related health resources. In addition, the elevated non-direct medical costs such as reduced productivity, traffic accidents, production accidents and consequent disabilities caused by drowsiness make the economic impact of OSA much higher than its direct medical costs. There is a lack of systematic research findings in this area in China.
Introduction to diabetes mellitus
Diabetes is a chronic hyperglycemic syndrome caused by absolute or relative lack of insulin and insulin resistance, which can cause acute complications of diabetes in severe cases, while long-term hyperglycemia can lead to tissue and organ damage, causing diabetic microvascular and macrovascular lesions. Diabetes mellitus is a common and frequent disease. With economic development, lifestyle changes, longer life expectancy and increased awareness of the disease, the number of people with diabetes is increasing year by year.
The World Health Organization (WHO) reported in 1997 that there were approximately 135 million people with diabetes worldwide, and this will rise to 300 million by 2025. The prevalence of diabetes is growing fastest in developing countries, and the growth in the number of people with diabetes in China over the past 30 years has been phenomenal, making it one of the three countries with the highest number of people with diabetes in the world. In developed countries, diabetes has become the third largest non-communicable disease after cardiovascular and tumor, and the danger of diabetes and its complications to public health is attracting more and more attention.
A nationwide survey conducted in 2007-2008 showed that the prevalence of diabetes in China is 9.7%, and the prevalence of pre-diabetes [impaired glucose tolerance (IGT) and impaired fasting glucose (IFG)] is 15.5%, which means that the number of people with diabetes in China is about 90 million. The direct medical cost of diabetes in 2003 was RMB 20.8 billion, accounting for 4.38% of the total medical cost in that year. In recent years, there have been studies or presentations on OSA and diabetes and insulin resistance in China.
OSA and abnormal glucose metabolism
The correlation between OSA and type 2 diabetes
Foreign cross-sectional studies between outpatients and populations have shown that the prevalence of diabetes is >40% in patients with OSA, while the prevalence of OSA can be more than 23% in diabetic patients and up to 58% in certain types of sleep disordered breath (SDB).
The results of the study showed that patients with OSA diagnosed by polysomnography (PSG) with apnea-hypopnea index (AHI, i.e., average number of apneas plus hypoventilation per hour of sleep) >10 times/h were more likely to have impaired glucose regulation and diabetes than those without OSA.
The findings showed that decreased oxygen saturation during sleep was significantly associated with fasting glucose and oral glucose tolerance test (OGTT) 2 h glucose concentrations, and the severity of OSA correlated with the degree of insulin resistance after correction for obesity parameters.Wisconsin et al. found that different degrees of OSA (those with mild to severe OSA after correction for obesity parameters) were associated with type 2 diabetes (OR=2.3 Two large studies found that snoring was an independent risk factor for the development of diabetes 10 years later.
The results of another large study showed that OSA was associated with the development of diabetes regardless of the duration of OSA. Sleep fragmentation and sleep quality in diabetic patients are important predictors of glycated hemoglobin (HbA1c). Continuous positive airway pressure (CPAP) ventilation improves insulin sensitivity and helps control blood glucose and lower HbA1c.
Mechanism of interaction between OSA and type 2 diabetes
In recent years, domestic and foreign research has been conducted on the mechanisms of OSA and type 2 diabetes correlation and possible intervention treatment methods. It is now believed that OSA can cause and aggravate type 2 diabetes mainly by the following mechanisms.
(1) Increased sympathetic nerve activity;
(2) Intermittent hypoxia;
(3) Hypothalamic-pituitary-adrenal (HPA) dysfunction;
(4) Systemic inflammatory response;
(5) Alterations in adipocytokines, such as elevated leptin levels and decreased adiponectin levels;
(6) Sleep deprivation. All of the above factors can lead to insulin resistance. In addition, autonomic dysfunction due to diabetes can also increase the risk of OSA, creating a vicious circle.
Periodic breathing (due to central dysfunction during sleep) is more common in diabetic patients than in non-diabetic patients. Another small study found that autonomic dysfunction in diabetic patients was associated with increased CO2 sensitivity of central chemoreceptors and decreased CO2 sensitivity of peripheral chemoreceptors. With 30% of this group of patients likely to have OSA without periodic breathing and central sleep apnea, further study of the role of autonomic dysfunction on upper airway collapse and control of breathing during sleep is clearly needed.
The results of the study showed that CPAP treatment significantly improved insulin sensitivity after 3 months and that CPAP treatment resulted in a significant reduction in HbA1c in poorly controlled diabetic patients. Obese OSA patients treated with CPAP for 12 weeks showed a reduction in visceral fat and lower leptin levels, but no improvement in glucose or insulin resistance. The effect was significant for those treated with CPAP for >4 h per night, while it was not significant for those treated for <4 h.
Improved early diagnosis of OSA and type 2 diabetes
Clinicians should consider the possibility of the presence of OSA in all patients with type 2 diabetes and metabolic syndrome, especially in the presence of.
(1) Snoring, daytime sleepiness ;
(2) Obesity, insulin resistance, and difficulty controlling diabetes mellitus;
(3) Intractable refractory hypertension, with morning hypertension as the prominent manifestation, and a non-arytenoid or anti-arytenoid circadian blood pressure rhythm;
(4) Nocturnal angina pectoris;
(5) Nocturnal intractable, severe and complex arrhythmias that are difficult to correct;
(6) Intractable congestive heart failure;
(7) Recurrent cerebrovascular disease (hemorrhagic or ischemic);
(8) Epilepsy;
(9) Alzheimer’s disease;
(10) Enuresis, increased nocturia;
(11) Sexual dysfunction;
(12) personality changes;
(13) Unexplained chronic cough;
(14) Unexplained erythrocytosis, etc.
If possible, patients with the above conditions should be examined for OSA and treated according to the appropriate guidelines.
The presence of diabetes mellitus should also be considered in patients with OSA in clinical practice. Patients with OSA without a history of diabetes should be screened for diabetes and assessed for the level and control of other cardiovascular risk factors. Treatment of diabetes mellitus and associated cardiovascular risk factors can be performed in accordance with the appropriate guidelines.
Prevention and Awareness
Immediate steps are recommended to inform health professionals and patients with diabetes about the basics of OSA and type 2 diabetes, clinical testing techniques, and related treatments. Health policy makers and the general public should also be aware of the economic burden of OSA on individuals and society, as well as the social harm it causes. The results of numerous studies have shown that overweight and obesity are the main independent risk factors for causing and aggravating OSA, and obesity is also a major risk factor for type 2 diabetes, so efforts must be made to control body weight for susceptible people. The main measures to control body weight are to implement a reasonable diet and to promote physical exercise.
Weight loss (through diet, exercise or surgery) can reduce the apnea index, and weight loss is one of the important treatment methods for overweight or obese patients. Weight loss reduces symptoms, improves social interaction, cognition, and work performance, and reduces accidents and erectile dysfunction in patients with OSA. In addition, reduced daytime fatigue increases stamina, improves glucose metabolism, and maintains body weight.
In addition, early and effective treatment of tonsillitis, pharyngitis, correction of small jaw deformities and mandibular recession, and aggressive treatment of deviated nasal septum and enlarged turbinates are also of special importance in the prevention of OSA.
Recommendations for scientific research
It is recommended that domestic physicians conduct further research in the following areas: (1) research on the prevalence and risk factors for OSA in patients with type 2 diabetes and metabolic syndrome; (2) research on the prevalence and risk factors for type 2 diabetes and metabolic syndrome in patients with OSA; (3) research on the mechanism of correlation between OSA and type 2 diabetes; (4) research on the relationship between OSA and the risk of complications of diabetes studies; (5) interventional studies: randomized controlled trials to understand the effects of treating OSA on glycemia, other cardiovascular risk factors, and clinical outcomes in diabetic patients; (6) development of treatment techniques: studies on easy methods to diagnose OSA in primary care hospitals; and search for simpler and less expensive methods to treat OSA than CPAP.
Recommendations for taking medical history
1. If sleep apnea is suspected, special attention should be paid to the following medical histories and symptoms.
(1) Ask bedmates and family members whether there is snoring during nighttime sleep, the degree of snoring (mild snoring: coarser than normal breathing; moderate snoring: snoring is louder than the sound of ordinary people talking; severe snoring: snoring is so loud that people in the same room cannot fall asleep), whether snoring is regular, and whether there is apnea;
(2) Whether waking occurs repeatedly;
(3) Whether there is an increase in nocturia;
(4) Dizziness, headache, and dry mouth in the morning;
(5) Daytime drowsiness and its degree;
(6) Progressive memory loss, personality changes such as impatience and irritability, abnormal behavior;
(7) Urine loss, sexual dysfunction;
(8) cardiovascular and cerebrovascular complications: including intractable refractory hypertension, especially the emergence of hypertension in the morning, angina pectoris at night, severe, complex, intractable arrhythmias, recurrent chronic heart failure, cerebrovascular disease, epilepsy, Alzheimer’s disease, etc.
2. In case of patients with sleep apnea, special attention should be paid to the following medical history and symptoms.
(1) the presence of chronic fatigue and weakness, discomfort and susceptibility to skin and genitourinary system infections;
(2) the presence of diabetes mellitus;
(3) the presence of recent abnormal fasting glucose, postprandial glucose or other (e.g. lipid) abnormalities, and the presence of a family history of diabetes, gestational diabetes and the birth of a large child.