Meta Analysis
Bariatric Surgery: A Systematic Review and Meta-analysis
This review may be edited
Posted By: Celia Bradford
Posted Date: 5 Aug 2005
Title: Bariatric Surgery: A Systematic Review and Meta-analysis
Authors: Buchwald, Henry MD, PhD; Avidor, Yoav MD; Braunwald, Eugene MD; Jensen, Michael D. MD; Pories, Walter MD; Fahrbach, Kyle PhD; Schoelles, Karen MD
Reference: JAMA; Volume 292(14), 13 October 2004, p 17241737
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: Context: About 5% of the US population is morbidly obese. This disease remains largely refractory to diet and drug therapy, but generally responds well to bariatric surgery.
Objective: To determine the impact of bariatric surgery on weight loss, operative mortality outcome, and 4 obesity comorbidities (diabetes, hyperlipidemia, hypertension, and obstructive sleep apnea).
Data Sources and Study Selection: Electronic literature search of MEDLINE, Current Contents, and the Cochrane Library databases plus manual reference checks of all articles on bariatric surgery published in the English language between 1990 and 2003. Two levels of screening were used on 2738 citations.
Data Extraction: A total of 136 fully extracted studies, which included 91 overlapping patient populations (kin studies), were included for a total of 22 094 patients. Nineteen percent of the patients were men and 72.6% were women, with a mean age of 39 years (range, 1664 years). Sex was not reported for 1537 patients (8%). The baseline mean body mass index for 16 944 patients was 46.9 (range, 32.368.8).
Data Synthesis: A random effects model was used in the meta-analysis. The mean (95% confidence interval) percentage of excess weight loss was 61.2% (58.1%64.4%) for all patients; 47.5% (40.7%54.2%) for patients who underwent gastric banding; 61.6% (56.7%66.5%), gastric bypass; 68.2% (61.5%74.8%), gastroplasty; and 70.1% (66.3%73.9%), biliopancreatic diversion or duodenal switch. Operative mortality (<=30 days) in the extracted studies was 0.1% for the purely restrictive procedures, 0.5% for gastric bypass, and 1.1% for biliopancreatic diversion or duodenal switch. Diabetes was completely resolved in 76.8% of patients and resolved or improved in 86.0%. Hyperlipidemia improved in 70% or more of patients. Hypertension was resolved in 61.7% of patients and resolved or improved in 78.5%. Obstructive sleep apnea was resolved in 85.7% of patients and was resolved or improved in 83.6% of patients.
Conclusions: Effective weight loss was achieved in morbidly obese patients after undergoing bariatric surgery. A substantial majority of patients with diabetes, hyperlipidemia, hypertension, and obstructive sleep apnea experienced complete resolution or improvement.
Are the Results Valid?
1. Did the overview address a focused clinical question?
Not really; the intervention of interest was bariatric surgery (all types) which is very broad. The population was identified as the morbidly obese, the outcomes were various (weight loss, and other obesity outcomes).
2. Were the criteria used to select articles for inclusion appropriate?
Follow-up of at least 50% of patients was needed for study inclusion. This is a VERY low follow-up rate.
Only English language publications were included. The studies had to include at least one outcome of interest. Kin relationship publications (double published data) were avoided.
3. Is it unlikely that important, relevant studies were missed?
The databases scanned were MEDLINE, Current Contents and the Cochrane Library. Search terms were broad. They did not search EMBASE however they did conduct a manual search of the reference lists of retrieved papers.
The authors limited their search to papers published after 1990. They provide not rationale justification for this limitation.
Authors have offered a bibliography of accepted and rejected studies.
4. Was the validity of the included studies appraised?
No. The methodological validity of the included studies was not assesssed.
5. Were assessments of studies reproducible?
There is no mention of more than one reviewer.
6. Were the results similar from study to study?
The authors report the presence of significant heterogeneity. Despite the use of a random effects model, it is possible that some of these articles should not have been pooled.
What are the Results?
1. What are the overall results of the overview?
The authors conclude: "Bariatric surgery in morbidly obese individuals reverses, eliminates, or significantly ameliorates diabetes, hyperlipidemia, hypertension, and obstructive sleep apnea. These benefits occur in the majority of patients who undergo surgery".
It is exteremly important to note that the claims are based on studies with significant loss to follow-up (up to 50%), with questionable methodological quality.
2. How precise were the results?
See abstract (above) for effect estimates and CIs.
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care
The risks, including mortality and morbidity of the surgery are not defined by this meta-analyis.
2. Were all clinically important outcomes considered?
No. Complications (Ex. Anaesthetic complication, length of hospital stay, wound infections etc) were not considered. Economics were not evaluated. Mortality was only reported for 50% of patients.
3. Are the benefits worth the harms and costs?
Impossible to tell. This meta-analysis tells me nothing to help me decide if a morbidly obese patient will be harmed by bariatric surgery.

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