The effect of Laparoscopic Sleeve Gastrectomy on Obstructive Sleep Apnea Syndrome

Background: The repeated episode of obstructive hypopnea and apnea during sleep is defined as obstructive sleep apnea (OSA) and it is a common condition in obese patients. Studies performing bariatric surgery have demonstrated a significant improvement in OSA by weight reduction. In this prospective study we aimed to explore the efficacy and safety of Laparoscopic Sleeve Gastrectomy (LSG) on OSAS among severely obese patients. Material and Methods: A total of 32 morbidly obese patients who underwent LSG for morbid obesity were included in this study. Body weight, height, body mass index (BMI) and standard overnight polysomnography (PSG) were measured at before and after LSG at the 6th month. Results: 32 patients (27 female, 5 male) who have postoperative PSG's were included in this study. The mean age was 43.22±9.87 years old. The mean preoperative and postoperative BMIs were 50.36±8.14kg/m2 and 37.27±7.93kg/m2, respectively. The mean Epworth sleepiness scale determined as 5.84±4.65 preoperatively and 2.19±3.55 postoperatively. The preoperative and postoperative sleep efficiency test of the patients was determined as 83.34±9.68 and 88.94±6.90 respectively. AHI average at the preoperative PSG was 31.47±26.34, while 9.35±10:34 at postoperative 6 months and found as statistically significant. Conclusion: Our data showed that LSG is an efficient and safe procedure on severely obese patients and showed a predictive remission of clinical and sleep parameters of patients with OSA by analyzing PSG data during the first 6 months.


Introduction
Recurrent episode of hypopnea or apnea during sleep is known as obstructive sleep apnea (OSA) (1).Obesity is one of the risc factor of this multifactorial disease (3).The prevalence of OSA range from 60-83% in patients planned for bariatric surgery (4).Nowadays popular bariatric surgery; Laparoscopic Sleeve Gastrectomy (LSG) is commonly performed because of its positive results on body weight loss and having less comorbidities (5).Some studies reported that after bariatric surgery patients had a high rate of improvement or resolution of obesity associated comorbidities such as diabetes, hypertension, hyperlipidemia and OSA (4,(6)(7)(8)(9).Studies after LSG based on polysomnography (PSG) for the evaluation of OSA are needed.
In this present study, we aimed to evaluate the efficiency of LSG by losing weight during the first 6 months for treating OSA by analyzing PSG findings obtained before and after surgery in morbidly obese patients

Study design and patients:
This study was performed at the department of general surgery of Antalya Education and Research Hospital and the clinical evaluation were performed at the Sleep Laboratory of the Ear Nose Throat Department.The consent of the Ethics Committee at Antalya Education and Research Hospital (2013/117) was achieved and additional informed consent was obtained from all individual participants for whom identifying information is included in this article.All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.Body weight and height were measured and Body Mass Index (BMI) was calculated.The following BMI grading system was implemented: normal range (BMI, 18.5-24.9kg/m2),overweight (BMI, 25-29.9kg/m2),obese (BMI, 30-34.9kg/m2), severely obese (BMI, 35-39.9kg/m2),morbid obese (BMI, 40-49.9kg/m2),super obese (BMI, ˃50 kg/m2).A total of 32 morbidly obese patients (5 male, 27 female), aged 19-62 years with a BMI ≥ 40 kg/m2, were operated on from July 2013 to February 2014.Follow-up inspections were carried out at the 6th month.Body weight, height, BMI and standard overnight PSG were measured before the operation and at the 6th month.
Surgical Procedure: All patients underwent standard five port laparoscopic sleeve gastrectomy by the same surgeon.It was made by Echelon 60 (Ethicon-Mexico) linear stapler.Postoperative care was uneventful and managed in the same manner.
Polysomnography Analysis: Patients suspected of narcolepsy, hypersomnolence, periodic limb movement disorders were excluded from the study.Patients with psychiatric or neurological disorders and major systemic co-morbidities were excluded.Epworth Sleepiness Scale (ESS) score was assessed for each patient using the validated Turkish version of the ESS questionnaire (10).The ESS questionnaire assesses the general level of daytime sleepiness by having individuals rate the likelihood of dozing during eight different daytime situations (scores 0-10).Body Mass Index (BMI) was calculated as weight (kg) divided by the height-squared (m2).
Obstructive apneas were defined as cessation of airflow for at least 10 s.Hypopneas were defined as periods of reduction of ˃ 30% oronasal airflow for at least 10 s and a ≥4% decrease in oxygen saturation.PSG data were manually scored according to the recommendations of the American Academy of Sleep by the same sleep technician under the supervision of an attending sleep specialist (11).An Apnea Hypoapnea Index (AHI) of 5-15/h is mild OSAS, an AHI of 15-30/h is moderate and AHI ˃30/h is severe OSAS, as assessed by polysomnography (12).

Statistical Analysis
The statistical analysis of the data was performed by using the SPSS 15.0 (SPSS Inc., Chicago, IL, USA) package program and Microsoft Office Excel version 2010.To comply with data of normal distribution One-Sample Kolmogorov-Smirnov test was used.In the comparison of data Mann-Whitney U test, Paired Samples Test, Wilcoxon test, Spearman's and Pearson's correlation tests were used.For the descriptive statistical analysis of the data: mean ± standard deviation and minimum-maximum values for numeric variables; numbers and percentages for categorical data were used.The level of p<0.05 was considered as significant.

Results
57 of 67 patients who planned bariatric surgery with a total of AHI˃5 revealed and preoperative PSG testing was performed.However, 32 patients who have postoperative PSG's were included in this study.27 of these patients were female (84%) and 5 were male (16%).The mean age of the patients was 43.22  AHI average at the preoperative PSG was 31.47 ± 26.34 (63.50-97.00),while 9.35 ± 10:34 (0.50-43.40) at postoperative 6 months and found as statistically significant (p <0.001).40.625% (n=13) of the patients included in this study have been identified as mild OSAS, 18.75% (n=6) moderate OSAS and 40.625% (n=13) severe OSAS.The postoperative AHI was detected under<5 in 16 (16%) patients, while it was found between 5-15 in 10 patients, between 15-30 in 3 patients and over˃30 in 3 patients.The preoperative and postoperative PSG findings of the patients are summarized in Table 2.
In the comparison of preoperative BMI and PSG findings, moderate positive correlation between nonsupine AHI and REM AHI (r = 0.546, r = 0.536), moderate negative correlation between the preoperative low oxygen saturation (r=-0.549)were found (Table 3).There was no significant correlation found at the comparison of postoperative BMI and PSG parameters (Table 4).

Discussion
Population based studies demonstrate OSAS affecting approximately 4% of males and 2% females (13).OSAS significantly increases the risk of stroke or death from any cause and in a community based sample moderate-to-severe sleep apnea is independently associated with a large increased risk of all-cause mortality.The obesity epidemic means problem faced by health professionals in relation to OSAS is only likely to increase in the immediate future (14).
Nowadays obesity is considered as one of the major risk factors for OSAS.The OSA rate is reported as 60-83% in patients with BMI≥35 kg/m2 and scheduled for bariatric surgery.(4,15).In our study, the prevalence of OSA was found to be 85.07% in patients with we have planned bariatric surgery.The higher rate of OSA may be associated with higher preoperative BMI (50.36 ± 8.14 (38.71-74.04)).
Surgical weight loss resulted in the significant improvement of OSA in obese individuals.As a result of the existing meta-analysis, data about the decline or improvement of OSA after bariatric surgery is available (4,6,16).
In one recent meta-analysis, it was suggested that in 359 subjects with a mean BMI of 55 kg/m2, surgery offered a weighted decrease of BMI by 16 kg/m2 (16.1, 95 % CI 13.3 to 18.9) and a weighted decrease of AHI by 34 events/h (34.2, 95 % CI 25.3 to 43.2) (4).
The first study reported at the 1980s and they defined a significantly decrease in the ratio of AHI after bariatric surgery.However in the study published in 1987, Charuz et al. reported a decrease of AHI from 58.8 to 36.1 with a weight loss of 70% at the 6 months after bariatric surgery (17).Valencia-Flores at al. reported the loss of OSAS and an improvement of oxygen saturation in 46% of patients having a decrease at BMI from 56.5 to 39.2 kg/m2 after bariatric surgery (18).
Dixon at al. in a study with more complete follow-up, observed after 17 months a reduction in excess weight of 50±15% and a decrease in AHI from 61.6±34 to 13.4±13 events/hour, in addition to a large improvement in quality of sleep, in diurnal somnolence and in quality of life (19).
It is of key importance to educate patients prior to bariatric surgery on OSAS: the high prevalence of OSAS in the bariatric surgery population, the risks of untreated OSAS, and need for appropriate treatment, especially since the effect of bariatric surgery on the AHI is not predictable.Ravesloot et al. have evaluated the postoperative PSG results with OSAS in two stages on patients they performed bariatric surgery.They reported a dramatically improvement on sleep parameters at the 7th months and a slower recovery in the coming months (20).
Various retrospective cohort studies in bariatric surgery show potential benefit in the treatment of OSA yet may not be termed curative.A key focus is required on meaningful long-term weight loss maintenance following surgery (21,22).
Bae et al. reported on bariatric surgery patients that postoperative residual OSA have more frequently seen in patients with preoperative low oxygen saturation and high preoperative supine AHI (23).
In our study, we observed high REM AHI in 11 (68.75%) of 16 patients with residual OSA (AHI ˃5).In our study it was also observed that the patients with residual OSA have preoperative low oxygen saturation (mean 73.75%).

Conclusions
In conclusion, our study have been showed that LSG is an efficient and safe procedure on severely obese patients and showed a predictive remission of clinical and sleep parameters of patients with OSAS by analyzing PSG during the first 6 months.

Table 2 :Table 2 :
Polysomnographic parameters before and 6 months after surgery

Table 3 :
The relationship between preoperative PSG findings with preoperative BMI