Dying to be thin: mortality after bariatric surgery

*Bethany Malone
Surgery, Summa Health System, United States
Michael Subichin
Surgery, Summa Health System, United States
Michael Firstenberg
Surgery, Summa Health System, United States
Joel Porter
Surgery, Summa Health System, United States

*Corresponding Author:

Bethany Malone
Surgery, Summa Health System
United States

Published on: 2017-06-19

Abstract

Introduction: Bariatric surgery is increasingly common. Sustained benefits include weight loss, diabetes resolution, and improved quality of life. Complications include malnutrition, depression, and substance abuse. Few studies examine long term mortality after bariatric surgery. We evaluated the mortality rate of patients with bariatric surgery compared to morbidly obese patients who did not undergo bariatric surgery.

Methods: We utilized de-identified patient data from 360 hospitals using the Explorys platform (Cleveland, OH). We identified 820,190 patients with the diagnosis of morbid obesity. We then determined the numbers of patients who underwent bariatric surgery, those who did not undergo bariatric surgery, and the in-hospital mortality rates of these groups. Chi Square test analysis was performed.

Results: 72,230 morbidly obese patients who underwent bariatric surgery were identified. Of these patients, 3,430 died resulting in a mortality of 4.75%. 747,960 non-surgical patients were identified with morbid obesity. 18,050 of these patients died resulting in a mortality of 2.3931%. The difference in mortality was statistically significant (p<0.001).

Conclusion: The current belief is that bariatric surgery improves patient mortality. This data set demonstrates increased all cause in hospital mortality after bariatric surgery. Large prospective trials are needed to elucidate this area.

Keywords

Bariatric surgery, Bariatric mortality, Morbid obesity.

Introduction

Obesity has reached epidemic proportions, affecting approximately 2 billion people worldwide.  WHO estimates that 39% of adults are overweight and 13% obese.  Multiple studies have cited obesity as a risk factor for diabetes, cardiovascular disease, hypertension, osteoarthritis, cerebrovascular disease, neoplasms, and decreased life expectancy.  Additionally, the per capita costs to the healthcare system for an obese adult are approximately 41.5% greater than those for a normal weight adult [1].  Obesity also shows geographically and racially disparate distributions, suggesting a multifactorial etiology.  In the Midwestern United States, obesity approaches the national average of around 32% [2].

The trend in obesity rates has lead to a subsequent rise in the surgical treatment of this disease.  Since the 1990s with the advent of laparoscopic surgery, bariatric surgeries in the United States have climbed from approximately 20,000 in 1992 to nearly 225,000 in 2010.  Additionally, the demographics of the bariatric surgery population differ drastically from the demographics of the morbidly obese population, with surgical patients tending to be middle aged white females while obesity tends to affect black and Hispanic populations preferentially with near gender equality [3].  With increasing numbers of bariatric surgery patients, an increasing amount of data has become available showing improvements in lifestyle, diabetes, activity level, and health-related quality of life both in short term and long-term studies [4],[5].  Bariatric surgery also has a unique set of operative complications, such as internal hernias, intussusceptions, and perforated ulcers at either the gastric pouch or gastric remnant; and a unique set of medical complications including dementia secondary to nutritional deficiencies, anemia, malnutrition, polysubstance abuse, and chronic nausea [6],[7].   Mortality rates after bariatric surgery have been conflicting, with most studies stating improved mortality after surgery, but mortality rates for morbidly obese patients range from 2% to 16% and mortality rates after bariatric surgery range from 1.5% to 11% in these studies [8].  With the known geographic variability of obesity and the discordance between the bariatric surgery population and the morbidly obese population, the existing literature may not apply to a particular provider’s patient population.  The purpose of this investigation is to compare the mortality rates between the bariatric population and the morbidly obese population in Northeast Ohio and surrounding areas using a retrospective database.

Method

We utilized de-identified patient data from 360 hospitals in Northeastern Ohio and the Midwestern United States using the Explorys database platform (Cleveland, OH). We performed a query using the terms “morbidly obese” and “morbid obesity” and identified 820,190 patients with the diagnosis of morbid obesity. Within this population, we used the search terms “gastric bypass,” “bariatric,” “Roux en Y,” “duodenal switch,” “sleeve gastrectomy,” and “bypass” to determine the number of patients who underwent bariatric surgery and those who did not undergo bariatric surgery. The in-hospital mortalities for each of these populations was then used to calculate the mortality rates for the bariatric surgery group and the morbidly obese group. The populations were then stratified by age and the mortalities calculated for these cohorts as well.

Statistical analysis was performed in Microsoft Excel 2010.  The mortality rates between the bariatric surgery and morbidly obese groups were compared using a Chi square test with a significance level of p<0.01.  Sub group analysis was then performed for the two cohorts based on age of pediatric (less than 18 years), adult (18-65 years), and geriatric (older than 65 years). The mortality rates in the subgroups were compared using a Chi square test with a significance level of p<0.01.  Linear regression analysis was then performed comparing mortality rate to age.

Result

In the Explorys database, 819,880 patients were identified with the diagnosis of morbid obesity.  The total mortality for this group was 21320 (2.600%).  This group was then divided into two cohorts.  The morbidly obese cohort without surgery contained a total of 747,650 patients with 17890 (2.393%) mortalities.  The bariatric surgery cohort contained a total of 72230 patients with 3430 (4.749%) mortalities.  The difference between the mortality rates was statistically significant (p<0.001) by a Chi Square test (Table 1).  The cohorts were then subdivided into pediatric, adult, and geriatric categories using age cutoffs of less than 18 years, ages 18-65 years, and then ages above 65 years.  The results are summarized in Table 2.  Because the majority of bariatric surgery patients were between the ages of 20 and 64, these patients were further subdivided by age and the mortalities of these groups calculated and shown in Table 3.  All mortality differences had a significance of p<0.001.  The mortality rates in the adult bariatric surgery cohort were then trended (Figure 1).  The patients in the age ranges with a mortality rate of 0% were then excluded and a linear regression analysis was performed in Microsoft Excel 2010 which resulted in a negative linear relationship between mortality rate and age with R = 0.8584.

Discussion

The results of this study conflict with much of the literature on the subject of mortality rates after bariatric surgery. While gastric bypass has been shown to reduce mortality rates, risk of myocardial infarction, angina pectoris, diabetes, and hypertension post-operatively compared to BMI matched patients, the post-bariatric surgery population still has increased mortality rates, myocardial infarction rates, and incidence of hypertension when compared with the general population [9]. The mortality rates in this study are also higher than those quoted in the literature for both the operative and non-operative groups [10]. One reason for this result is that this study specifically looks at all cause in hospital mortality and is not limited to patients who only follow up at the institution that performed the index procedure due to the pooling of multiple hospital data into the database. By including data from multiple hospitals, patients who may travel for their surgery but receive emergency care closer to home are still included, even though they may be missed by many traditional study designs. Additionally, post-operative patients are more likely to seek medical care and have higher inpatient admission rates when compared to BMI matched peers [11].

When reviewing the bariatric mortality literature, most of the data regarding short term and long-term mortality tends to focus on disease specific mortality. However, when looking at all-cause mortality in the bariatric surgery population, Adams, et al., found increased long-term mortality rates in post-operative bariatric surgery patients when compared to BMI matched patients [11]. The surgery group still maintained reduced disease specific mortality rates when compared to the non-operative cohort. While the metabolic benefits of bariatric surgery have been shown, 10%-45% of the adult obese population is metabolically healthy. These patients tend to be younger and female [12]. These metabolically healthy individuals may have limited benefits from metabolic surgery, which may explain the increased mortality rates in the younger bariatric surgery population shown in this study. Metabolism and cardiovascular risk are major factors in the ultimate morbidity and mortality of obese patients, but other contributing factors have not been as clearly elucidated in this patient population.

Many efforts have been made to prognosticate morbidity and mortality risk for these procedures. Multiple mortality risk calculators have been developed based on NSQIP data [13]. These risk calculators take into account patient age, BMI, history of thromboembolism, peripheral vascular disease, history of percutaneous cardiac intervention, steroid use, and type of bariatric surgery performed. While these risk assessments can help identify 30-day risk of mortality, many were designed with 1-2 year follow up. They have limited prognostic value for open gastric bypass [14] and can have inconsistent results when used in different hospital systems [15]. These risk calculators fail to predict morbidity risk of these procedures and have limited applicability to re-operative bariatric surgery [16]. While having a convenient calculator can be helpful for pre-operative discussions with patients, the ultimate goal of metabolic surgery is to benefit the patient beyond a 30 day or even 2-year mark. Other risk factors for mortality after bariatric surgery include congestive heart failure and chronic renal failure [17]. While many of these risk factors are intuitive, they still do not help to identify the subset of obese patients who will have limited benefit from these procedures and may be exposed to undue risk.

Beyond patient factors, surgeon factors also affect post-operative outcomes. Birkmeyer, et al., found that bariatric surgeons who were graded by their peers as more proficient had a five-fold decrease in mortality rates, one third the complication and reoperation rates, and half the readmission rates when compared to less proficient colleagues [18]. Both surgeon and hospital volumes in bariatric surgery are also related to decreased mortality rates [19], which suggests that Bariatric Centers of Excellence should focus both on peer assessed surgeon skill as well as case volume in order to minimize undue risks to patients choosing metabolic surgery.

Additionally, the indications for bariatric surgery continue to increase, with proposed appropriate comorbidities including severe mental illness [20], hypogonadism [21], chronic steroid use [22], and pre-transplant [23]. With expanding indications for these procedures, little data exists to adequately quantify or stratify patients at highest risk for mortality. The types of procedures performed under the category of bariatric surgery have continued to evolve, with formerly common operations such as jejuno-ileal bypass or gastric banding becoming of historical or re-operative significance. Not only have the included patient populations and types of procedures performed changed over time, but the types of hospitals covered by Medicare and Medicaid for these procedures will also increase. In 2006, the Centers for Medicare and Medicaid Services instituted the National Coverage Determination that restricted covered bariatric procedures to only those performed at designated Bariatric Centers of Excellence, which resulted in improved morbidity and mortality outcomes for these beneficiaries [24]. However, the National Coverage Determination has recently been lifted which will increase the number of hospitals and introduce more variability in surgeon experience for bariatric surgery patients. The rapidly increasing indications for surgery coupled with the increasing variety of hospitals and surgeons performing the procedure should call into question the applicability of previously published outcomes literature.

Conclusion

While the current popular belief in the surgical community is that bariatric surgery reduces mortality rates in the bariatric population, this study indicates that this may not hold true for patients in Northeast Ohio and the surrounding areas. Further prospective research is necessary to delineate which subsets of morbidly obese patients are most appropriate for surgical intervention.

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