A high incidence of obstructive sleep apnoea in severely obese Asians-especially in the Chinese
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《中华医药杂志》英文版
[Abstract] Objective To evaluate the incidence of obstructive sleep apnoea in severely obese Asians.Methods We report the results of routine pre-operative sleep studies (nocturnal polysomnograms) in 300 Asian patients undergoing bariatric surgery in our institution since 2001.Results The prevalence of OSA in severely obese Asians is high. Moderate or severe OSA (apnoea hypopnoea index AHI of 15 per hour or more) was found in 46% of patients and severe OSA (AHI 30 per hour or more) was found in 33%. Although severe obesity is less common in Chinese population, severe OSA was seen significantly more in the Chinese (46%) compared to the Malays (29%) or Indians (21%) (P=0.035).We identified other risk factors for severe OSA (male sex, higher body mass index and the presence of hypertension) but were unable to select a group of patients in whom the likelihood of severe OSA was so low (<5%) that routine sleep study could be omitted.Conclusions A high incidence of OSA in Asian population undergoing bariatric surgery exists.The our policy of routine sleep studies is justified as severe OSA is not predicted reliably by other means. The significantly higher incidence of severe OSA in the Chinese compared to the Malays and Indians is probably related to racial differences in facial architecture.
[Key words] obesity;sleep apnoea obstructive;polysomnography;Asia;Chinese
INTRODUCTION Obstructive sleep apnoea(OSA)is common in the severely obese[1~3] and its presence is associated with an increased anaesthetic risk during and soon after bariatric surgery due to adverse cardio-respiratory events[4]. This risk can be reduced by getting patients with severe OSA to use nasal CPAP pre,peri- and post-operatively to normalize the AHI4. CPAP acts as a pneumatic splint to keep the pharyngeal airway open during sleep and to maintain the lungs volume.
Many attempts have been made to predict the presence of OSA in obese patients based on sleep history or clinical parameters, but a sleep study is the only method to reliably detect OSA[1,3].
The incidence of OSA in severely obese Asian patients is poorly documented. We have a policy of routine pre-operative sleep studies in our Asian population undergoing bariatric surgery. This has allowed us to assess the frequency of OSA and to look at racial differences within our multi-cultural society.
METHODS
Bariatric surgery was introduced at our hospital in 2001 as part of a multidisciplinary weight management program.We now perform an average of 10 laparoscopic adjustable gastric bands (LAGB) each month and we have the largest experience of this procedure in East Asia. We used Asian criteria in selecting patients for bariatric surgery[5]. Patients must have BMI 32.5 and above with obesity-related co-morbidity or BMI 37.5 and above with or without co-morbidity.
As part of the pre-operative workup all our patients underwent overnight sleep study scored using standard criteria. We based our diagnosis of OSA primarily on the apnoea hypopnoea index. An AHI index of 15/h and above is taken to indicate significant OSA and an AHI of 30/h and above indicates severe OSA.
Department of Surgery, Alexandra Hospital, 378 Alexandra Road,159964 Singapore
* Currently Consultant General and Bariatric Surgeon at Raffles Private Hospital, Singapore
Correspondence to Dr Trevor Leese MBBS, FRCS,MD Senior Consultant Surgeon and Chairman of Bariatric Surgery,Alexandra Hospital,378 Alexandra
Road,159964 Singapore
Tel: ++ 65 63793488, Fax: ++ 65 63793540, E-mail: tbleese54@hotmail.com
Patients with severe OSA were fitted with a nasal mask and a CPAP machine during sleep at home for at least two weeks prior to surgery. They continued to use CPAP during the surgical admission and at home for at least two weeks post-operatively.
We analysed the results of sleep studies in our first 300 patients to look at the incidence of OSA and predictors of OSA including racial differences within our multicultural population. Statistical analysis was with the chi-square test, Mann Whitney U test and Spearman's rho (2-tailed) test.
RESULTS
Patient demographics were given in Table 1.
Table 1 Patient demographics
*Note:dyslipidaemia, metabolic syndrome, gout, non-alcoholic steatohepatitis (NASH), shortness of breath, gastroesophageal reflux, obstructive sleep apnoea, excessive daytime slee, snoring, menstrual irregularities, sub-fertility, depression, stress, social isolation.
95% of our patients completed overnight sleep studies. 138 patients (46%) had significant OSA (AHI 15/h or greater) and 99 patients (33%) had severe OSA (AHI 30/h or greater). Analysis of clinical factors associated with OSA confirmed an increased risk of OSA in males, higher body weight, higher BMI, higher excess weight and in the presence of hypertension (Table 2),but no individual factor or combination of factors could be identified which reliably predicted the absence of severe OSA (<5% chance).
Table 2 Positive correlations with AHI
* Mann Whitney U test
**Spearman's rho (2-tailed)
Table 3 Correlation between race and the presence of severe OSA (%)
*P=0.035,Chi-square test
The racial differences in our patients were shown in Table 3. The Chinese accounted for 76.8% of the population of Singapore but only 43% of the severely obese patients undergoing bariatric surgery. There was a higher prevalence of obesity in the Malays and Indians. The risk of severe OSA in the severely obese Chinese is significantly higher than the risk in Malay or Indians even though the distribution of sex, weight, excess weight, BMI and hypertension is similar across the three racial groups.
DISCUSSION
Bariatric surgery is exploding onto the scene in Asia as the obesity pandemic spreads to the East. We owe it to our patients to keep surgery as safe as possible.
Obesity is a risk factor for OSA and OSA increases the peri-operative risk during bariatric surgery as well as longer-term risks of hypertension, heart disease, stroke, diabetes and depression[2]. OSA can be predicted using sleep history, clinical criteria or scoring systems based on 1 or 2 of these, but these methods will not reliably detect all patients at risk. Neck circumference, hypertension, habitual snoring, bed partner reporting of gasping/choking[6], BMI, age and gender[7] have been reported as independent predictors of OSA. Scoring systems such as the Berlin Questionnaire, Epworth sleepiness scale[8], and other multifactorial scoring systems[9] have been used to predict OSA, but again none was totally reliable.
Routine sleep studies are expensive and a limited resource but they guarantee that this potentially lethal co-morbidity is detected and treated appropriately. A policy of routine sleep studies increased the detection rate of OSA in the severely obese from 8%~48%[10] to 71%~98%[1~3] with severe OSA detected in 32.7%[2].
Sleep study data on Asian patients is scarce. Our data clearly showed that OSA is common in severely obese Asian patients. This high incidence had been noted by others[11] and supported a policy of routine sleep studies in the severely obese[1,3], especially in Chinese patients. From information stored in our prospective database we were unable to select a group of patients with such a low risk of OSA (<5%) that routine sleep study could be avoided.
The exceptionally high risk of OSA in severely obese Chinese is probably related to racial differences in craniofacial and upper airway morphology[11,12] which have also been documented in the Japanese[13].
OSA improves markedly with weight loss[10] and bariatric surgery is the only reliable method for achieving long-term weight loss in the severely obese. In our Asian population percentage excess weight loss one year after LAGB is 50.4% (range 9%~117.5%). We have noted marked improvement is sleep patterns in our patients and we plan to repeat sleep studies to document the improvement in OSA associated with successful weight loss.
REFERENCES
1.O'Keeffe T, Patterson EJ. Evidence supporting routine polysomnography before bariatric surgery. Obes Surg，2004，14:23-26.
2.Valencia-Flores M, Orea A, Castano VA, et al. Prevalence of sleep apnoea and electrocardiographic disturbances in morbidly obese patients. Obesity Research，2000，8:262-269.
3.Frey WC, Pilcher J. Obstructive sleep-related breathing disorders in patients evaluated for bariatric surgery. Obes Surg，2003，13:676-683.
4.Doherty LS, Kiely JL, Swan V, et al. Long-term effects of nasal continuous positive airway pressure therapy on cardiovascular outcomes in sleep apnoea syndrome. CHEST，2005，127:2076-2084.
5.Ministry of Health Clinical Practice Guidelines on Obesity - revision card. Ministry of Health, Singapore, 2005.
6.Flemons WW, Whitelaw WA, Brant R, et al. Likelihood ratios for a sleep apnoea clinical prediction rule. Am J Respir Crit Care Med，1994，150:1279-1285.
7.van Boxem TJ, de Groot GH. Prevalence and severity of sleep disordered breathing in a group of morbidly obese patients. Neth J Med，1999，54:202-206.
8.Serafini FM, MacDowell Anderson W, Rosemurgy AS, et al. Clinical predictors of sleep apnoea in patients undergoing bariatric surgery. Obes Surg，2001，11:28-31.
9.Dixon JB, Schachter LM, O'Brien PE. Predicting sleep apnea and excessive daytime sleepiness in the severely obese: indicators for polysomnography. CHEST，2003，123:1134-1141.
10.Dixon JB, Schachter LM, O'Brien PE. Sleep disturbance and obesity: changes following surgically induced weight loss. Arch Intern Med，2001，161:102-106.
11.Li KK, Kushida C, Powell NB, et al. Obstructive sleep apnoea syndrome: a comparison between Far-East Asian and white men. Laryngoscopy，2000，110:1689-1693.
12.Lam B, Ooi CG, Peh WC, et al. Computed tomographic evaluation of the role of craniofacial and upper airway morphology in obstructive sleep apnea in Chinese. Respir Med，2004，98:301-307.
13.Sakakibara H, Tong M, Matsushita K, et al. Cephalometric abnormalities in non-obese and obese patients with obstructive sleep apnoea. Eur Respir J，1999，13:403-410.
(Editor Jaque)(Ganesh R,Rao AL,Baladas H)
[Key words] obesity;sleep apnoea obstructive;polysomnography;Asia;Chinese
INTRODUCTION Obstructive sleep apnoea(OSA)is common in the severely obese[1~3] and its presence is associated with an increased anaesthetic risk during and soon after bariatric surgery due to adverse cardio-respiratory events[4]. This risk can be reduced by getting patients with severe OSA to use nasal CPAP pre,peri- and post-operatively to normalize the AHI4. CPAP acts as a pneumatic splint to keep the pharyngeal airway open during sleep and to maintain the lungs volume.
Many attempts have been made to predict the presence of OSA in obese patients based on sleep history or clinical parameters, but a sleep study is the only method to reliably detect OSA[1,3].
The incidence of OSA in severely obese Asian patients is poorly documented. We have a policy of routine pre-operative sleep studies in our Asian population undergoing bariatric surgery. This has allowed us to assess the frequency of OSA and to look at racial differences within our multi-cultural society.
METHODS
Bariatric surgery was introduced at our hospital in 2001 as part of a multidisciplinary weight management program.We now perform an average of 10 laparoscopic adjustable gastric bands (LAGB) each month and we have the largest experience of this procedure in East Asia. We used Asian criteria in selecting patients for bariatric surgery[5]. Patients must have BMI 32.5 and above with obesity-related co-morbidity or BMI 37.5 and above with or without co-morbidity.
As part of the pre-operative workup all our patients underwent overnight sleep study scored using standard criteria. We based our diagnosis of OSA primarily on the apnoea hypopnoea index. An AHI index of 15/h and above is taken to indicate significant OSA and an AHI of 30/h and above indicates severe OSA.
Department of Surgery, Alexandra Hospital, 378 Alexandra Road,159964 Singapore
* Currently Consultant General and Bariatric Surgeon at Raffles Private Hospital, Singapore
Correspondence to Dr Trevor Leese MBBS, FRCS,MD Senior Consultant Surgeon and Chairman of Bariatric Surgery,Alexandra Hospital,378 Alexandra
Road,159964 Singapore
Tel: ++ 65 63793488, Fax: ++ 65 63793540, E-mail: tbleese54@hotmail.com
Patients with severe OSA were fitted with a nasal mask and a CPAP machine during sleep at home for at least two weeks prior to surgery. They continued to use CPAP during the surgical admission and at home for at least two weeks post-operatively.
We analysed the results of sleep studies in our first 300 patients to look at the incidence of OSA and predictors of OSA including racial differences within our multicultural population. Statistical analysis was with the chi-square test, Mann Whitney U test and Spearman's rho (2-tailed) test.
RESULTS
Patient demographics were given in Table 1.
Table 1 Patient demographics
*Note:dyslipidaemia, metabolic syndrome, gout, non-alcoholic steatohepatitis (NASH), shortness of breath, gastroesophageal reflux, obstructive sleep apnoea, excessive daytime slee, snoring, menstrual irregularities, sub-fertility, depression, stress, social isolation.
95% of our patients completed overnight sleep studies. 138 patients (46%) had significant OSA (AHI 15/h or greater) and 99 patients (33%) had severe OSA (AHI 30/h or greater). Analysis of clinical factors associated with OSA confirmed an increased risk of OSA in males, higher body weight, higher BMI, higher excess weight and in the presence of hypertension (Table 2),but no individual factor or combination of factors could be identified which reliably predicted the absence of severe OSA (<5% chance).
Table 2 Positive correlations with AHI
* Mann Whitney U test
**Spearman's rho (2-tailed)
Table 3 Correlation between race and the presence of severe OSA (%)
*P=0.035,Chi-square test
The racial differences in our patients were shown in Table 3. The Chinese accounted for 76.8% of the population of Singapore but only 43% of the severely obese patients undergoing bariatric surgery. There was a higher prevalence of obesity in the Malays and Indians. The risk of severe OSA in the severely obese Chinese is significantly higher than the risk in Malay or Indians even though the distribution of sex, weight, excess weight, BMI and hypertension is similar across the three racial groups.
DISCUSSION
Bariatric surgery is exploding onto the scene in Asia as the obesity pandemic spreads to the East. We owe it to our patients to keep surgery as safe as possible.
Obesity is a risk factor for OSA and OSA increases the peri-operative risk during bariatric surgery as well as longer-term risks of hypertension, heart disease, stroke, diabetes and depression[2]. OSA can be predicted using sleep history, clinical criteria or scoring systems based on 1 or 2 of these, but these methods will not reliably detect all patients at risk. Neck circumference, hypertension, habitual snoring, bed partner reporting of gasping/choking[6], BMI, age and gender[7] have been reported as independent predictors of OSA. Scoring systems such as the Berlin Questionnaire, Epworth sleepiness scale[8], and other multifactorial scoring systems[9] have been used to predict OSA, but again none was totally reliable.
Routine sleep studies are expensive and a limited resource but they guarantee that this potentially lethal co-morbidity is detected and treated appropriately. A policy of routine sleep studies increased the detection rate of OSA in the severely obese from 8%~48%[10] to 71%~98%[1~3] with severe OSA detected in 32.7%[2].
Sleep study data on Asian patients is scarce. Our data clearly showed that OSA is common in severely obese Asian patients. This high incidence had been noted by others[11] and supported a policy of routine sleep studies in the severely obese[1,3], especially in Chinese patients. From information stored in our prospective database we were unable to select a group of patients with such a low risk of OSA (<5%) that routine sleep study could be avoided.
The exceptionally high risk of OSA in severely obese Chinese is probably related to racial differences in craniofacial and upper airway morphology[11,12] which have also been documented in the Japanese[13].
OSA improves markedly with weight loss[10] and bariatric surgery is the only reliable method for achieving long-term weight loss in the severely obese. In our Asian population percentage excess weight loss one year after LAGB is 50.4% (range 9%~117.5%). We have noted marked improvement is sleep patterns in our patients and we plan to repeat sleep studies to document the improvement in OSA associated with successful weight loss.
REFERENCES
1.O'Keeffe T, Patterson EJ. Evidence supporting routine polysomnography before bariatric surgery. Obes Surg，2004，14:23-26.
2.Valencia-Flores M, Orea A, Castano VA, et al. Prevalence of sleep apnoea and electrocardiographic disturbances in morbidly obese patients. Obesity Research，2000，8:262-269.
3.Frey WC, Pilcher J. Obstructive sleep-related breathing disorders in patients evaluated for bariatric surgery. Obes Surg，2003，13:676-683.
4.Doherty LS, Kiely JL, Swan V, et al. Long-term effects of nasal continuous positive airway pressure therapy on cardiovascular outcomes in sleep apnoea syndrome. CHEST，2005，127:2076-2084.
5.Ministry of Health Clinical Practice Guidelines on Obesity - revision card. Ministry of Health, Singapore, 2005.
6.Flemons WW, Whitelaw WA, Brant R, et al. Likelihood ratios for a sleep apnoea clinical prediction rule. Am J Respir Crit Care Med，1994，150:1279-1285.
7.van Boxem TJ, de Groot GH. Prevalence and severity of sleep disordered breathing in a group of morbidly obese patients. Neth J Med，1999，54:202-206.
8.Serafini FM, MacDowell Anderson W, Rosemurgy AS, et al. Clinical predictors of sleep apnoea in patients undergoing bariatric surgery. Obes Surg，2001，11:28-31.
9.Dixon JB, Schachter LM, O'Brien PE. Predicting sleep apnea and excessive daytime sleepiness in the severely obese: indicators for polysomnography. CHEST，2003，123:1134-1141.
10.Dixon JB, Schachter LM, O'Brien PE. Sleep disturbance and obesity: changes following surgically induced weight loss. Arch Intern Med，2001，161:102-106.
11.Li KK, Kushida C, Powell NB, et al. Obstructive sleep apnoea syndrome: a comparison between Far-East Asian and white men. Laryngoscopy，2000，110:1689-1693.
12.Lam B, Ooi CG, Peh WC, et al. Computed tomographic evaluation of the role of craniofacial and upper airway morphology in obstructive sleep apnea in Chinese. Respir Med，2004，98:301-307.
13.Sakakibara H, Tong M, Matsushita K, et al. Cephalometric abnormalities in non-obese and obese patients with obstructive sleep apnoea. Eur Respir J，1999，13:403-410.
(Editor Jaque)(Ganesh R,Rao AL,Baladas H)