Original Article
Characterization of primary symptoms leading to Chinese patients presenting at hospital with suspected obstructive sleep apnea Zhe Li1, Lina Du1, Yun Li1, Lili Huang2, Fei Lei1, Linghui Yang1, Tao Li1, Xiangdong Tang1 1
Sleep Medicine Center, Mental Health Center, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041,
China; 2Pharmaceutical College, Heilongjiang University of Chinese Medicine, Harbin 150040, China Correspondence to: Prof. Xiangdong Tang, MD. Sleep Medicine Center, West China Hospital, Sichuan University, 28 Dian Xin Nan Jie, Chengdu 610041, China. Email: [email protected].
Objectives: We identified the primary symptoms leading to Chinese patients presenting at hospital with suspected obstructive sleep apnea (OSA) and studied the prevalence and characteristics of OSA in confirmed cases. Methods: We collected data on 350 consecutive patients (302 males and 43±11 years old) with suspected OSA who underwent overnight polysomnography (PSG). Results: Among all patients, rankings of primary symptoms that led to the patients presenting at hospital for PSG were observed apnea (33%), snoring alone (29%), choking/gasping (13%), daytime sleepiness (5%) and other (20%). For severe OSA, prevalence rate was 61%, apnea hypopnea index (AHI) was 64±18, age was 44±10 years old, body mass index (BMI) was 28±3.5 kg/m2, and hypertension rate was 28%. Conclusions: Self-awareness of symptoms led a majority of the patients to present at hospital in China. Compared to currently available case series studies, our results suggest that OSA patients in East Asian countries are characterized by higher prevalence and more severe apnea, younger age, poorer sleep quality, but less obesity and less comorbidity with hypertension, relative to countries in North America, South America and Europe. Keywords: Apnea; symptoms; prevalence; consecutive patients Submitted Nov 28, 2013. Accepted for publication Feb 18, 2014. doi: 10.3978/j.issn.2072-1439.2014.02.08 View this article at: http://www.jthoracdis.com/article/view/2340/2925
Introduction Obstructive sleep apnea (OSA) is highly common in the general population and may affect 9% to 17% of adults with higher rates in men (1). Recurring episodes of apnea during sleep is the central pathological component of OSA, but symptoms and associated illnesses vary among individual patients. Symptoms typically include loud snoring, witnessed episodes of apnea during sleep, gasping and daytime sleepiness. OSA also has significant comorbidity with hypertension, cardiovascular diseases, stroke and diabetes as well as other illnesses (2). Effective treatment, even for mild OSA patients, may ameliorate comorbid conditions. Though symptoms vary among OSA patients, there are
© Pioneer Bioscience Publishing Company. All rights reserved.
two primary reasons for which potential patients present to a sleep laboratory for polysomnography (PSG). Patients may be self-aware of symptoms and seek medical assistance or they may be referred by a physician who notes OSA related symptoms in patients who have presented with hypertension, heart diseases, stroke or other comorbidities. Patient’s self-awareness may largely arise from public awareness programs whereas referral likely reflects the cognizance of OSA by physicians. Clarifying these issues would be valuable for strategizing for the development and improvement of respiratory sleep medicine. For example, a low number of referred OSA patients would suggest that we may need to increase education related to respiratory sleep medicine knowledge to physicians. Further, these two patient pools could influence the evaluation and
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J Thorac Dis 2014;6(5):444-451
Journal of Thoracic Disease, Vol 6, No 5 May 2014
445
Table 1 Number and percentage of PSG prescriptions ranked according to the outpatient departments where the patients initially presented Department
Number
%
Sleep center
189
54.0
E.N.T.
113
32.3
Respiratory
23
6.6
Others
25
7.1
350
100.0
Total
PSG, polysomnography; E.N.T., ear, nose and throat.
characterization of OSA as well as differentially skew data regarding OSA prevalence in hospital based studies. For instance, if the data include fewer referred OSA patients, the average age of the pool may be younger. In the present investigation, we used a case series approach to identify the primary symptoms that lead to patients presenting at our sleep medicine center in China. However, many complicated factors may impact the characteristics of OSA prevalence across races and countries, including biological and socioeconomic factors (3). In the current study, we found a particularly young average age and high prevalence of severe OSA in patients with suspected OSA. To further evaluate potential differences specific to Chinese OSA patients, we therefore compared our results to those in studies of populations of other countries in order to assess potential demographic differences in age and prevalence of severe OSA across nationalities. Methods Subjects The data were collected from October, 2011 to December, 2011 at the Sleep Medicine Center of West China Hospital, Sichuan University (Chengdu, China). During this three months period, 350 (302 males and 48 females, average age 42.9±11.0 years old) consecutive patients with suspected OSA were referred to take an overnight PSG. Data from a subset of these patients, as identified below, were used in the study. This study was approved by the Research Ethics Board of the West China Hospital of Sichuan University. Clinical data collection Prior to PSG recording, clinic data collection mainly included three steps. First, we recorded the information
© Pioneer Bioscience Publishing Company. All rights reserved.
concerning PSG prescribed by the physicians across departments. The results were summarized in Table 1. Second, routine information was collected for all patients who underwent PSG in our sleep medicine center. These included checklists for general information (e.g., age and gender, totally seven items), symptoms (e.g., snoring, observed apnea and leg movement, choking and morning headache, totally 13 items), comorbidities (e.g., hypertension and heart disease, totally ten items), lifestyle (smoking and alcohol, totally five items) and a checklist for physical examination (height, body weight, blood pressure and pharyngeal tonsils, totally ten items). The Epworth daytime sleepiness scale (ESS) was also evaluated. However, we only present some of most important data in Table 2. Third, we specifically identified the primary symptoms that led to the patients presenting at the sleep medicine center for PSG for this study. In this step, we attempted to classify the primary symptoms as a distinct category. For example, patients presenting with a complaint of loud snoring alone with no other symptoms were classified as “snoring”. However, many patients might have multiple symptoms. We carefully investigated what the single primary issue that led to present the hospital. For example, if a patient had symptoms of snoring, observed episodes of apnea, daytime sleepiness and hypertension, he might answered that “my wife observed the apnea and pushed me to come to the hospital”, he then would be classified as “observed apnea”; if his answer was daytime sleepiness, he would be recognized into that category; if he stated that due to “I have suffered from hypertension and PSG was prescribed by my doctor of internal medicine”, he would be categorized as “hypertension”. In fact, most patients could clearly identify as one of them. However, if the patients presented with insomnia, regardless of whether the patients were suspected of OSA, they would be placed into an insomnia category in our registration system and excluded from the investigation. Overnight PSG The diagnosis of OSA was established by a standard overnight PSG. Overnight PSG consisted of continuous recordings from six electroencephalographic leads (F3-A2, F4-C1, C3-A2, C4-A1, O1-A2, O2-A1, international 10-20 system), two electrooculographic leads (ROCA1, LOC-A2), four electromyography leads (two submental and bilateral tibialis anterior), thermistors for nasal and oral airflow, strain gauges for thoracic and abdominal excursion,
www.jthoracdis.com
J Thorac Dis 2014;6(5):444-451
Li et al. Primary symptoms in Chinese obstructive sleep apnea (OSA)
446
Table 2 Clinical and polysomnographic characteristics in each group of AHI
Characterization of primary symptoms leading to Chinese patients presenting at hospital with suspected obstructive sleep apnea Zhe Li1, Lina Du1, Yun Li1, Lili Huang2, Fei Lei1, Linghui Yang1, Tao Li1, Xiangdong Tang1 1
Sleep Medicine Center, Mental Health Center, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041,
China; 2Pharmaceutical College, Heilongjiang University of Chinese Medicine, Harbin 150040, China Correspondence to: Prof. Xiangdong Tang, MD. Sleep Medicine Center, West China Hospital, Sichuan University, 28 Dian Xin Nan Jie, Chengdu 610041, China. Email: [email protected].
Objectives: We identified the primary symptoms leading to Chinese patients presenting at hospital with suspected obstructive sleep apnea (OSA) and studied the prevalence and characteristics of OSA in confirmed cases. Methods: We collected data on 350 consecutive patients (302 males and 43±11 years old) with suspected OSA who underwent overnight polysomnography (PSG). Results: Among all patients, rankings of primary symptoms that led to the patients presenting at hospital for PSG were observed apnea (33%), snoring alone (29%), choking/gasping (13%), daytime sleepiness (5%) and other (20%). For severe OSA, prevalence rate was 61%, apnea hypopnea index (AHI) was 64±18, age was 44±10 years old, body mass index (BMI) was 28±3.5 kg/m2, and hypertension rate was 28%. Conclusions: Self-awareness of symptoms led a majority of the patients to present at hospital in China. Compared to currently available case series studies, our results suggest that OSA patients in East Asian countries are characterized by higher prevalence and more severe apnea, younger age, poorer sleep quality, but less obesity and less comorbidity with hypertension, relative to countries in North America, South America and Europe. Keywords: Apnea; symptoms; prevalence; consecutive patients Submitted Nov 28, 2013. Accepted for publication Feb 18, 2014. doi: 10.3978/j.issn.2072-1439.2014.02.08 View this article at: http://www.jthoracdis.com/article/view/2340/2925
Introduction Obstructive sleep apnea (OSA) is highly common in the general population and may affect 9% to 17% of adults with higher rates in men (1). Recurring episodes of apnea during sleep is the central pathological component of OSA, but symptoms and associated illnesses vary among individual patients. Symptoms typically include loud snoring, witnessed episodes of apnea during sleep, gasping and daytime sleepiness. OSA also has significant comorbidity with hypertension, cardiovascular diseases, stroke and diabetes as well as other illnesses (2). Effective treatment, even for mild OSA patients, may ameliorate comorbid conditions. Though symptoms vary among OSA patients, there are
© Pioneer Bioscience Publishing Company. All rights reserved.
two primary reasons for which potential patients present to a sleep laboratory for polysomnography (PSG). Patients may be self-aware of symptoms and seek medical assistance or they may be referred by a physician who notes OSA related symptoms in patients who have presented with hypertension, heart diseases, stroke or other comorbidities. Patient’s self-awareness may largely arise from public awareness programs whereas referral likely reflects the cognizance of OSA by physicians. Clarifying these issues would be valuable for strategizing for the development and improvement of respiratory sleep medicine. For example, a low number of referred OSA patients would suggest that we may need to increase education related to respiratory sleep medicine knowledge to physicians. Further, these two patient pools could influence the evaluation and
www.jthoracdis.com
J Thorac Dis 2014;6(5):444-451
Journal of Thoracic Disease, Vol 6, No 5 May 2014
445
Table 1 Number and percentage of PSG prescriptions ranked according to the outpatient departments where the patients initially presented Department
Number
%
Sleep center
189
54.0
E.N.T.
113
32.3
Respiratory
23
6.6
Others
25
7.1
350
100.0
Total
PSG, polysomnography; E.N.T., ear, nose and throat.
characterization of OSA as well as differentially skew data regarding OSA prevalence in hospital based studies. For instance, if the data include fewer referred OSA patients, the average age of the pool may be younger. In the present investigation, we used a case series approach to identify the primary symptoms that lead to patients presenting at our sleep medicine center in China. However, many complicated factors may impact the characteristics of OSA prevalence across races and countries, including biological and socioeconomic factors (3). In the current study, we found a particularly young average age and high prevalence of severe OSA in patients with suspected OSA. To further evaluate potential differences specific to Chinese OSA patients, we therefore compared our results to those in studies of populations of other countries in order to assess potential demographic differences in age and prevalence of severe OSA across nationalities. Methods Subjects The data were collected from October, 2011 to December, 2011 at the Sleep Medicine Center of West China Hospital, Sichuan University (Chengdu, China). During this three months period, 350 (302 males and 48 females, average age 42.9±11.0 years old) consecutive patients with suspected OSA were referred to take an overnight PSG. Data from a subset of these patients, as identified below, were used in the study. This study was approved by the Research Ethics Board of the West China Hospital of Sichuan University. Clinical data collection Prior to PSG recording, clinic data collection mainly included three steps. First, we recorded the information
© Pioneer Bioscience Publishing Company. All rights reserved.
concerning PSG prescribed by the physicians across departments. The results were summarized in Table 1. Second, routine information was collected for all patients who underwent PSG in our sleep medicine center. These included checklists for general information (e.g., age and gender, totally seven items), symptoms (e.g., snoring, observed apnea and leg movement, choking and morning headache, totally 13 items), comorbidities (e.g., hypertension and heart disease, totally ten items), lifestyle (smoking and alcohol, totally five items) and a checklist for physical examination (height, body weight, blood pressure and pharyngeal tonsils, totally ten items). The Epworth daytime sleepiness scale (ESS) was also evaluated. However, we only present some of most important data in Table 2. Third, we specifically identified the primary symptoms that led to the patients presenting at the sleep medicine center for PSG for this study. In this step, we attempted to classify the primary symptoms as a distinct category. For example, patients presenting with a complaint of loud snoring alone with no other symptoms were classified as “snoring”. However, many patients might have multiple symptoms. We carefully investigated what the single primary issue that led to present the hospital. For example, if a patient had symptoms of snoring, observed episodes of apnea, daytime sleepiness and hypertension, he might answered that “my wife observed the apnea and pushed me to come to the hospital”, he then would be classified as “observed apnea”; if his answer was daytime sleepiness, he would be recognized into that category; if he stated that due to “I have suffered from hypertension and PSG was prescribed by my doctor of internal medicine”, he would be categorized as “hypertension”. In fact, most patients could clearly identify as one of them. However, if the patients presented with insomnia, regardless of whether the patients were suspected of OSA, they would be placed into an insomnia category in our registration system and excluded from the investigation. Overnight PSG The diagnosis of OSA was established by a standard overnight PSG. Overnight PSG consisted of continuous recordings from six electroencephalographic leads (F3-A2, F4-C1, C3-A2, C4-A1, O1-A2, O2-A1, international 10-20 system), two electrooculographic leads (ROCA1, LOC-A2), four electromyography leads (two submental and bilateral tibialis anterior), thermistors for nasal and oral airflow, strain gauges for thoracic and abdominal excursion,
www.jthoracdis.com
J Thorac Dis 2014;6(5):444-451
Li et al. Primary symptoms in Chinese obstructive sleep apnea (OSA)
446
Table 2 Clinical and polysomnographic characteristics in each group of AHI
