CRD summary

This review concluded that both early and late mortality rates after bariatric surgery were low and could be used for prospective risk assessments and stratification. The overall findings of the review should be interpreted with caution, given concerns about the review methods and the quality of the data on which they are based.

Authors' objectives

To review published mortality data following any form of bariatric surgery.

Searching

MEDLINE, Current Contents Connect and the Cochrane Library were searched for English language studies published from January 1990 to April 2006. Search terms were reported. Manual searches of reference lists and recent reviews were also carried out.

Study selection

Studies reporting mortality data for at least 10 patients undergoing any type of bariatric surgery, who were followed-up for at least 30 days, were eligible for inclusion in the review. Studies using data from large databases or registries were excluded from the review, due to the potential overlap of data. Reports using the same patient group were only counted once. Studies where the length of follow-up was unclear, or where mixed treatment groups were used and the data not reported separately, were also excluded.

The majority of studies included in the review were of gastric bypass surgery or gastric banding, most using laparoscopic rather than open surgery. Studies were retrospective and mainly used a single arm design. The mean age of included patients was 40 years (range 16 to 65 years) and the mean body mass index was 47.4 kilograms per metre squared (kg/m²). The majority of patients were female (85%) and 11.5% had had previous bariatric surgery. Commonly reported comorbidities included arthritis, hypertension and dyslipidemia. The majority of studies were carried out in North America (57.6%) and Europe (34.7%).

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

Assessment of study quality

The authors assessed the validity of randomised controlled trials (RCTs) using the Jadad scale. Each RCT was awarded a score between 0 and 5 points. The quality of other study designs did not appear to have been assessed.

The authors did not state how many reviewers assessed the validity of the studies or how discrepancies were resolved.

Data extraction

Early (within 30 days of the surgery) and late (>30 days to 2 years) mean percentage mortality rates were extracted. Mortality data collected two years or more after surgery was not included. Zero mortality was assumed where other data were reported and it was clear there were no deaths. Raw weighted means were calculated for patient characteristics.

The authors did not state how data were extracted for the review, or how many reviewers performed the data extraction.

Methods of synthesis

Studies were grouped by type of surgery (i.e. gastric banding, gastroplasty, gastric bypass and biliopancreatic diversion with or without duodenal switch) and then by type of procedure (i.e. restrictive, mixed restrictive plus malabsorptive, and malabsorptive). Restricted maximum-likelihood random-effects meta-analyses were carried out. Pooled mean percentage mortality rates with 95% confidence intervals were reported. The Cochran Q statistic was used to calculate statistical heterogeneity. Subgroup analyses according to year of publication, patient gender, patient age, comorbidities and size of study were also performed.

Results of the review

Three hundred and sixty-one studies (n=85,048 patients) with 478 treatment arms were included in the review. Only four studies were classified as providing class I evidence. Nineteen of the studies were randomised. The majority of studies (67.9%) were retrospective and most (87%) were only single arm studies. Further details about the quality of the studies were not reported.

Mortality according to procedure: Total early mortality (475 treatment arms and 84,931 patients) was 0.28% (95% confidence interval (CI): 0.22 to 0.34) and late mortality (140 treatment arms and 19,928 patients) was 0.35% (95% CI: 0.12 to 0.58). Rates were usually lower in laparoscopic procedures compared open surgery, with the exception of biliopancreatic diversion/duodenal switch and late mortality in gastric bypass procedures. Significant statistical heterogeneity was reported for the analyses of early mortality in biliopancreatic diversion/duodenal switch, and late mortality in open gastric bypass procedures. Higher mortality rates were also associated with revision surgery and malabsorptive procedures. Further details were reported in the review.

Mortality according to subgroups: Higher mortality rates were reported for all subgroups, with the exception of females and adolescents, as compared with the population as a whole. Super-obese patients were also reported to have higher early and late mortality rates. Despite small numbers of studies, male subgroups were reported to have higher early mortality rates than female subgroups, but this was only based on 22 patients. In elderly patients (at least 65 years old), late mortality was found to be lower than early mortality. Further details and results were reported in the review.

Authors' conclusions

Both early and late mortality rates after bariatric surgery were low and could be used to carry out prospective risk assessments and risk stratification for comparative analyses.

CRD commentary

This review answered a clear research question using a broad range of study designs, patients and interventions. Searches were carried out for published studies in a number of electronic databases, but relevant studies may have been missed through the exclusion of non-English language articles and the apparent lack of any specific attempts to locate unpublished studies. It is also unclear whether precautions were taken to reduce the risk of reviewer error and bias when selecting, extracting and assessing the quality of the included studies. Study validity was assessed using the Jadad scale, but details of this assessment, along with important details about the design of the studies, were not reported, even in summary form. The quality of other study designs (98% of studies) was not assessed. This makes it difficult to assess the reliability of the data, although it is likely to be poor given the reliance on mainly single arm studies. The authors also noted that significant statistical heterogeneity was detected for some of the analyses and rightly report that mortality rates between the different interventions and subgroups were not comparable. Overall, the review findings should be interpreted with caution given concerns about the review methods and the quality of the study data.

Implications of the review for practice and research

Practice: The authors stated that data from a meta-analysis such as this can provide the necessary information for institutions, carriers, government health agencies and patients under the care of physicians/bariatric surgeons, to assess the risk of death from bariatric surgery.

Research: The authors stated that, in order to assess the risk of death from bariatric surgery, further research is required to develop an assessment tool comparing risks in different populations, between high and low volume centres, different locations and using different databases. They also stated that this review may serve as a foundation for such a tool.

Funding

Ethicon Endo-Surgery (a Johnson & Johnson company).

Bibliographic details

Buchwald H, Estok R, Fahrbach K, Banel D, Sledge I. Trends in mortality in bariatric surgery: a systematic review and meta-analysis. Surgery 2007; 142(4): 621-635. [PubMed: 17950357]

Original Paper URL

http://www.surgjournal.com/article/S0039-6060(07)00492-8/abstract

Indexing Status

Subject indexing assigned by NLM

MeSH

Bariatric Surgery /mortality; Comorbidity; Humans; Obesity, Morbid /mortality /surgery; Risk Assessment

AccessionNumber

12008103200

Database entry date

12/08/2009

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.