Introduction

Bariatric surgery is the most effective intervention to provide substantial and durable weight loss [1]. Laparoscopic sleeve gastrectomy (LSG) is the most commonly performed bariatric surgery in the USA, accounted for over 50% of all cases [2]. Compared with Roux-en-Y gastric bypass (RYGB), long-term outcomes of LSG are relatively less well described, especially in non-Western populations as it is a relatively newer procedure. An increasing number of studies have suggested that LSG can provide effective and sustainable weight loss with the average of about 50% excess weight loss (%EWL) at 5 years after surgery, similar to the average of about 60% EWL at 5 years after RYGB [3]. The surgical revision rate was 13% due to weight regain and 3% due to gastroesophageal reflux disease (GERD) at 7 years or more after LSG [4]. However, these data are predominantly from the Western countries that may not be generalizable to other populations. Some studies have shown racial disparities in the outcomes of bariatric surgery, in which LSG may be less effective among Asians [5,6,7]. Moreover, the obesity phenotype of Asians may be different from that of Caucasians as Asians tend to have higher body fat and visceral fat compared with Caucasians despite lower body weight [8,9,10], resulting in a higher risk of type 2 diabetes and metabolic syndrome.

The current meta-analysis aimed to comprehensively identify all available studies that reported midterm outcomes (up to 5 years) of LSG in Asian populations to better characterize the efficacy and complications of LSG among these populations.

Materials and Methods

Search Strategy

Two authors (PU and VJ) independently searched for published articles indexed in Ovid/MEDLINE and EMBASE databases from inception to August 2019 using the search term of “sleeve gastrectomy.” No language restriction was applied. Reviews, case reports, and letters were excluded. References of selected retrieved articles were also manually reviewed for additional potentially relevant studies.

Eligibility Criteria

Eligible observational studies or randomized controlled trials must meet all of the following inclusion criteria: (1) participants were adults (age of more than or equal to 18 years old) with obesity who underwent LSG; (2) the follow-up duration was at least 3 years; (3) % total body weight loss (TBWL) and/or %EWL at 3 and/or 5 years were reported; and (4) the study was conducted in an Asian country. Two authors (PU and VJ) independently reviewed the eligibility of the retrieved articles. Disagreements were identified and discussed with all authors. If there were more than one eligible study that reported data from the same group of patients, only one study with most comprehensive information was selected for inclusion.

Data Extraction

The following data were independently extracted by the same 2 authors using a standardized study record form: first author name; country where the study was conducted; year of publication; study design; baseline characteristics of the patients; number of the patients at follow-up; %TBWL and %EWL at 1, 3, and 5 years; surgical revision rate; and complications. For randomized controlled trials, data were extracted only from LSG arm (i.e., data from non-LSG participants were not used). The corresponding authors of the included articles were contacted if additional data were required for the meta-analyses.

Statistical Analysis

The %TBWL and %EWL at 1, 3, and 5 years after LSG, complication, and surgical revision rate were extracted from each study. The pooled effect size and 95% confidence interval (CI) were calculated using a random effects model. The heterogeneity of effect size estimates across the studies was quantified using the Q statistic and I2 (P < 0.10 was considered significant). An I2 value of 0–25% indicates insignificant heterogeneity, 26–50% indicates low heterogeneity, 51–75% indicates moderate heterogeneity, and 76–100% indicates high heterogeneity [11]. Publication bias was assessed using funnel plots. All analyses were performed using the Comprehensive Meta-Analysis program, version 2.2 (Biostat, Englewood, NJ, USA).

Results

The initial search yielded 16,704 potentially relevant articles (13,222 articles from EMBASE and 3,482 articles from MEDLINE). After the exclusion of 2,175 duplicated articles, 14,529 articles underwent title and abstract review. A total of 14,482 articles were excluded at this stage, as they clearly did not fulfill the eligibility criteria, leaving 47 articles for full-length review. Thirty articles were excluded after a full-length review with reasons shown in Supplementary File 1. Finally, 19 studies [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28] involving 6,235 Asian patients with obesity who underwent LSG met the eligibility criteria and were included into the meta-analyses. The detailed characteristics of the included studies are described in Table 1. In brief, most studies had more women (% female 40.0–94.4) patients than men. The sample sizes ranged from 15 to 1,759 patients. The mean age ranged from 29.3 to 40.7 years. The mean baseline body mass index ranged from 31.8 to 46.7 kg/m2.

Table 1 Characteristics of the included studies
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Weight Reduction After Laparoscopic Sleeve Gastrectomy

For %EWL, 14 [13, 15,16,17,18, 20,21,22, 24,25,26, 28,29,30], 16 [13,14,15,16,17,18,19,20,21,22, 24,25,26,27, 29, 30], and 10 [12, 13, 16, 17, 22,23,24,25,26, 28] studies involving 4027, 1317, and 911 patients reported %EWL at 1, 3, and 5 years, respectively. The pooled mean %EWLs were 72.6% (95% CI 67.2–78.0, I2 = 97%); 67.1% (95% CI 61.7–72.6, I2 = 95%); and 59.1% (95% CI 48.8–69.4, I2 = 94%) at 1, 3, and 5 years, respectively (Fig. 1).

Fig. 1
figure 1

Forest plots of % excess weight loss at 1 year, 3 years, and 5 years after LSG

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For %TBWL, 5 [15, 17, 25, 28, 29], 5 [14, 15, 17, 25, 29], and 3 [17, 25, 28] studies (reviewer 1) involving 1922, 202, and 375 patients reported %TBWL at 1, 3, and 5 years, respectively. The pooled mean %TBWLs were 32.1% (95% CI 30.0–34.2, I2 = 94%); 29.0% (95% CI 25.0–33.1, I2 = 91%); and 25.5% (95% CI 20.4–30.6, I2 = 69%) at 1, 3, and 5 years, respectively (Fig. 2).

Fig. 2
figure 2

Forest plots of % total body weight loss at 1 year, 3 years, and 5 years after LSG

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Revisional Surgery After Laparoscopic Sleeve Gastrectomy

A total of 9 and 6 studies reported the rate of surgical revision because of GERD and weight regain, respectively. The pooled rates of revision due to GERD and weight regain were 1.9% (95% CI 1.2–2.9%, I2 = 20%) and 2.5% (95% CI 0.9–6.3%, I2 = 89%), respectively (Fig. 3).

Fig. 3
figure 3

Forest plots of surgical revision rate due to gastroesophageal reflux disease and weight regain

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Post-operative Complications

Fifteen studies reported the complications in detail [12,13,14,15, 17,18,19,20,21,22,23,24,25,26,27]. From 2,676 patients, 150 early post-operative complications (5.6%) occurred (most studies defined early complications as within 30 days after surgery). The most common early complications were bleeding (43 patients, 1.6%, ranging from 0 to 5.6%), followed by leaks (34 patients, 1.3%, ranging from 0 to 2.8%), wound infection (31 patients, 1.2%, ranging from 0 to 6.4%), and wound dehiscence (21 patients, 0.8%, ranging from 0 to 10%). Uncommon complications included gastric stenosis (5 patients), atelectasis (4 patients), bowel injury (2 patients), deep vein thrombosis (2 patients), port site hernia (2 patients), abdominal wall abscess (2 patients), perforation (1 patient), and splenic injury (1 patient). Out of 150 early complications, 48 patients required interventions for their complications. Late complications included GERD (43 patients), stricture (1 patient), and esophageal dysmotility (1 patient). There were 2 deaths after LSG (0.07%); one was from pneumonia and the other one was due to respiratory failure from undiagnosed obstructive sleep apnea.

Publication Bias

Funnel plots were created from the 3 analyses with the highest number of studies including %EWL at 1 year, 3 years, and 5 years to evaluate for the presence of publication bias. All 3 funnel plots were relatively symmetric and were not suggestive of presence of publication bias (Fig. 4).

Fig. 4
figure 4

Funnel plots of % excess weight loss at 1 year, 3 years, and 5 years after LSG

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Discussion

LSG is an effective and durable bariatric surgery that has gained worldwide popularity, including Asia. However, it is a relatively newer procedure compared with RYGB that has recently been endorsed as a stand-alone primary bariatric surgery by the American Society Bariatric and Metabolic Surgery (ASMBS) in 2012 [31]. In addition, its largest body of evidence comes from Western populations that its efficacy and complications in Asians with obesity are still not well described.

The current study took the advantage of a systematic review and meta-analysis technique to summarize data from all available studies. We found that the mean EWL at 1, 3, and 5 years after surgery surpass the minimal cutoff of 50% EWL recommended by the ASMBS to be considered a successful weight loss tool and the efficacy is sustainable for up to 5 years. Interestingly, the current study observed the maximal weight loss at 1 year with a slight decline in weight reduction at 3 years, which is different from observations of the previous systematic review that included studies from every region around the world that found the maximal weight loss at 3 years after LSG [32].

The need for surgical revision is a major concern of patients who undergo LSG. The two most common indications are weight regain/insufficient weight loss and GERD. Our meta-analysis including studies with a follow-up duration of more than 3 years found a pooled surgical revision rate for weight regain of only 2.5%, which is lower than the pooled revision rate of 13.1% reported by a meta-analysis that included data from all regions of the world. Nonetheless, it should be noted that the previous meta-analysis included studies of a longer follow-up period (7 years or more) [4]. De novo or worsening GERD is another drawback of LSG as a result of high intragastric pressure associated with the sleeved stomach and the possible disruption of the lower esophageal sphincter from the transection of the sling fibers [33, 34]. A multicenter study involving 90 patients demonstrated a high prevalence of Barrett’s esophagus of almost 20% after 5 years of LSG [35]. The current study found a pooled revision rate for GERD of 1.9% among Asian patients compared with the pooled revision rate of 2.9% for GERD from the previous global meta-analysis [4]. It should be noted that the diagnostic criteria for GERD have not been well described in our included studies.

Despite the advantage of the systematic review and meta-analysis technique that comprehensively summarizes all available data, the current study has some limitations that may affect the validity of our pooled results. First, this current study is a meta-analysis of descriptive studies that is generally considered of lower quality and most of the included studies were retrospective studies, in which the reported data could be incomplete and/or inaccurate. Second, the primary studies included in this meta-analysis had a high loss to follow-up rate. Therefore, the results could be skewed if patients who failed to show up were significantly different from the analyzed patients. Some of the included studies tried to increase the follow-up rate by reaching out to patients who did not return for follow-up visit using telephone interview. However, information gathered by this approach could be less reliable. Third, high between-study heterogeneity was observed, which could be a result of different study protocols and patient populations.

In conclusion, the current meta-analysis suggested that LSG is an effective procedure for weight reduction that offers durable response for up to 5 years among Asians with obesity. In addition, the observed surgical revision rate appears to be lower than previously reported data from other populations. Further studies of long-term efficacy of this procedure (> 5 years) are warranted.