Effectiveness of surgical weight loss on the remission of type 2 diabetes mellitus: A systematic review

Abstract

Review questions/objectives The review objective is to synthesize the best available evidence regarding the effectiveness of surgical weight loss procedures on the remission of type 2 diabetes mellitus. The review questions are: What are the short-term (< 2 years) and long-term (> 2 years) effects of surgical weight loss procedures on weight reduction and hemoglobin A1c values in patients with type 2 diabetes mellitus? Do surgical weight loss procedures eliminate or reduce the need for antidiabetic medications short-term (< 2 years) and/or long-term (> 2 years) in patients with type 2 diabetes mellitus? Background Diabetes and obesity are at an all time high. More than 1.1 billion adults worldwide are overweight with 312 million obese1, and over two-thirds of adults in the United States are overweight or obese with 7.8 percent of the population having diabetes mellitus2, 3. According to the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) the terms overweight and obese are categorized utilizing “body mass index” or BMI. BMI in adults is a calculation based upon weight and height. Adults with a BMI between 25 and 29.9 are considered overweight (or pre-obese) and a BMI greater than 30 is considered obese.4, 5 According to the European Association for the Study of Obesity (EASO) overweight rates in Finland, Germany, Greece, Cyprus, the Czech Republic, Slovakia and Malta go beyond those of the United States of America (USA).5 Some parts of Europe have a combined overweight and obesity prevalence greater than the 67% found in the USA. 5 Obesity is a global health dilemma that affects all ages, genders, and nationalities. Obesity is best defined as an amassing of excess body fat that potentiates adverse health outcomes.5 Severe obesity (BMI > 40) has been linked to a 12-fold increase in mortality among 25 to 35 year old individuals. 5 Obesity is linked to cancer, stroke, obstructive sleep apnea and arthritis, as well as psychosocial issues stemming from discrimination and prejudice.5 The most common chronic conditions associated with obesity are heart disease and type 2 diabetes mellitus (T2DM). Morbidity and mortality associated with diabetes reach well beyond the United States. The World Health Organization (WHO) has declared diabetes a global epidemic that kills as many people as HIV and AIDS. WHO estimates 3.4 million persons died as a result of diabetes related complications in 2004 and project this number to double by 20306.The Western Pacific Region has the highest prevalence of people with diabetes and impaired glucose tolerance with 77 million and 120 million respectively1. The estimated worldwide diabetes prevalence is 285 million or 6.8% of the global adult population1. Medical costs associated with diabetes and its complications are likely to deplete U.S. Medicare dollars before our younger generations reach retirement age. Diabetes mellitus is the seventh leading cause of death in the United States with a total direct and indirect cost of $218 billion2, 7. According to the International Diabetes Federation (IDF) global healthcare expenditures to treat and prevent diabetes, hyperglycemia and related complications is projected to reach or exceed 490 billion U.S. dollars by the year 20301. Weight loss is defined as the reduction of body mass by deliberate (diet and/or exercise) or unintentional (illness and/or disease) means.8 Purposeful weight loss resulting in loss of excess body fat contributes to enhanced health outcomes such as lower blood pressure, lower cholesterol, reduced blood glucose levels, and reduced mortality. 9 Weight loss has been shown to improve and even resolve the presence of type T2DM clinical manifestations.10-12 The clinical practice guidelines (CPG) from the American Diabetes Association, 11 the Canadian Diabetes Association,12 and the Malaysian Diabetes Association10 as well as the Malaysian CPG for obesity9 all recommend the use of surgical weight loss procedures as a treatment option for obese patients with T2DM. Surgical weight loss procedures have proven successful as treatment for severe obesity, and national guidelines support its consideration for people with T2DM who have a body mass index > 35 kg/m211. Surgical weight loss has been shown to lead to near or complete normalization of blood glucoses in approximately 55-95% of patients with T2DM11. Types of surgical weight loss procedures include biliopancreatic diversion, jejunoileal bypass, Roux-en-Y or gastric bypass, gastric banding, and gastric sleeve. These procedures provide restriction and/or malabsorption of orally consumed nutrients. Table 1 provides more detail on the most common surgical weight loss procedures.13Table 1: Comparison of Different Surgical Weight Loss ProceduresBuchwald et al. reported a resolution of T2DM by 48% for laparoscopic adjustable gastric banding (LABG), 84% for gastric bypass, and 98% for biliopancreatic diversion (BPD) or duodenal switch14. They concluded that 82% of diabetes patients who underwent a surgical weight loss procedure experienced resolution or remission of diabetes < 2 years after surgery with 62% sustained > 2 years after surgery14. Resolution or remission of type 2 diabetes mellitus is defined as a normal fasting blood glucose level (< 100mg/dL) or HgbA1C < 6.0% with no antidiabetic medications.14 Elimination of the need for antidiabetic medications refers to the absence of antidiabetic medications, while reduction refers to decrease in dosage or decrease in types of antidiabetic medications.14 A convenience sample of surgical weight loss (SWL) patients from a nonacademic teaching hospital in the United States was reviewed; 79 patients with diabetes - 33 gastric bypass & 46 LABG15. 6 months post surgery the following short-term outcomes were achieved (long-term outcomes have not yet been evaluated): Gastric bypass: 80.65 lb average weight loss, 55.2% elimination of T2DM medications, and 75.9% reduction of HgbA1C to normal levels (< / = 6%) LABG: 37.49 lb average weight loss, 59.5% elimination of T2DM medications, and 56.7% reduction of HgbA1C to normal levels (< / = 6%) 7. These outcomes are impressive and appear to prove surgical weight loss as a potentially effective treatment option for T2DM obesity-related issues. We performed a search of Cochrane Library of Systematic Reviews, JBI Library of Systematic Reviews, CRD DARE database and Medline and found only one systematic review regarding surgical weight loss procedures on the remission of type 2 diabetes mellitus. The review by Buchwald et al. was published in 2008 and contains literature from January 1990 to April 2006 and includes studies other than RCTs.14 The amount of literature published since 2006 warrants completion of a JBI systematic review to establish a sound evidence-based recommendation inclusive of the most current research and practices. Inclusion criteria Types of participants This review will consider studies that include all patients 18 years of age and older, females and males with a prior diagnosis of type 2 diabetes mellitus who have undergone a bariatric surgical weight loss procedure. Types of intervention(s)/phenomena of interest This review will consider studies that evaluate the effects of surgical weight loss procedures. Types of outcomes This review will consider studies that include the following outcome measures indicating the remission of type 2 diabetes mellitus: weight loss, body mass index (BMI), hemoglobin A1C values, fasting blood glucose levels, and/or reduction/elimination of antidiabetic medications. Types of studies This review will consider any randomized controlled trial (RCTs); in the absence of RCTs other research designs, such as non-randomized controlled trials will be considered for inclusion to enable the identification of current best evidence regarding the effects of surgical weight loss procedures on the remission of type 2 diabetes mellitus. Search strategy The search strategy aims to find both published and unpublished studies in English language only from April 2006 through May 2011. A three-step search strategy will be utilized. An initial limited search of MEDLINE and CINAHL will be undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Thirdly, the reference list of all identified reports and articles will be searched for additional studies. The databases to be searched include: MEDLINE (1950 to present), AMED, OVID All EBM Reviews (collection includes Cochrane DSR, ACP Journal Club, DARE, CCTR, CMR, HTA, & NHSEED), CINAHL, EMBASE, TRIP, NGC, EBSCO, PubMed, Current Contents, ProQuest, Science Direct, and Expanded Academic ASAP. The search for unpublished studies will include: AHRQ (Agency for Healthcare Research and Quality), Evidence Reports, Digital Dissertations - DAI, Google Scholar, SIGLE (System for Information on Grey Literature in Europe), The New York Academy of Medicine, Gray Literature Report Networked Digital Library of Theses and Dissertations (NDLTD), Scirus, and Mednar. Initial keywords to be used: obesity/surgery, gastrectomy, gastric bypass, bariatric, gastric banding, Roux-en-Y, gastric sleeve, biliopancreatic diversion, jejunoileal bypass, AND diabetes mellitus. Assessment of methodological quality Quantitative papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardised critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion, or with a third reviewer. Data collection Quantitative data will be extracted from papers included in the review using the standardized data extraction tool from JBI-MAStARI (Appendix II). The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. Data synthesis Quantitative papers will, where possible be pooled in statistical meta-analysis using the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI). All results will be subject to double data entry. Odds ratio (for categorical data) and weighted mean differences (for continuous data) and their 95% confidence intervals will be calculated for analysis. Heterogeneity will be assessed using the standard Chi-square. Where statistical pooling is not possible the findings will be presented in narrative form. Conflicts of interest none