Trends and variation in the prevalence of obesity and related comorbidities

The prevalence of obesity in the United States has steadily increased over the past two decades (Map 2). While less than 15% of the population was obese in each state in 1990, by 2010, all 50 states had rates greater than 20%, and 39 had rates greater than 25%. Moreover, in 15 states in the eastern and central U.S., more than 30% of the population was obese.

Map 2.

Obesity trends among U.S. adults. BMI ≥30, or about 30 lbs. overweight for 5’4” person.

Figure 3.

Burden of obesity among Americans (2009-10).

Just as rates of obesity differ across the United States, the rates of other illnesses associated with obesity also vary across the country. For example, the incidence of type II diabetes varies across the United States (Figure 4), with the highest rates of diabetes evident in southeastern regions (Map 3), where rates of obesity are also high. The national average rate of type II diabetes during 2010-11 was 23%. Less than 15% of Medicare beneficiaries living in the Colorado hospital referral regions of Grand Junction (14.1%) and Boulder (14.1%) had type II diabetes during 2010-11. The incidence of type II diabetes was more than twice as high among Medicare beneficiaries living in the Texas hospital referral regions of McAllen (38.5%), Harlingen (38.5%), and Corpus Christi (30.3%).

Figure 4.

Percent of Medicare beneficiaries with type II diabetes among hospital referral regions (2010-11). Each blue dot represents the rate of type II diabetes in one of 306 hospital referral regions in the U.S. Red dots indicate the regions with the 5 lowest (more...)

Map 3.

Percent of Medicare beneficiaries with type II diabetes (2010-11). Rates are adjusted for age, sex, and race.

Treatment options and success rates

Treatments for obesity can be classified into medical and surgical therapies. Medical therapies include lifestyle modification or medications that limit fat absorption, such as orlistat. The long-term effectiveness of these therapies is modest for most patients. Medical therapies generally lead to an initial loss of 3-10% of body weight,^4-8 but sustained weight loss requires the indefinite continuation of therapy, which can be difficult for many patients.

Surgical therapy, while more invasive, is also more efficacious. In bariatric surgery, the gastrointestinal tract (the stomach and/or intestines) is modified or reconstructed to promote weight loss. Many of the initial procedures performed by surgeons—such as jejunocolic bypass, jejunoileal bypass, and vertical banded gastroplasty—had significant adverse effects and have been abandoned.⁹ Currently, the most common bariatric, or weight-loss, procedures currently offered to patients are adjustable gastric banding, sleeve gastrectomy, and Roux-en-Y gastric bypass (Figure 5). In the past, a traditional open surgical approach was used for these procedures, but the overwhelming majority of bariatric surgery today is performed via laparoscopy, using small cameras and instruments inserted into the abdomen in a less invasive approach.

Figure 5.

Three commonly performed bariatric procedures.

Bariatric procedures vary in complexity. Adjustable gastric banding—the least complex option—involves the placement of a synthetic, inflatable band around the stomach to create a small gastric pouch and a restricted gastric outlet, which limits food and caloric intake (Figure 5A). A sleeve gastrectomy, in contrast, removes part of the stomach, leaving a narrow sleeve, which preserves gastrointestinal continuity but restricts food and caloric intake (Figure 5B). In Roux-en-Y gastric bypass—the most complex of the three commonly offered procedures—the stomach is divided to create a small gastric pouch, the small intestine is divided, and the distal segment of small intestine (the part of the intestine further away from the stomach) is surgically connected to the gastric pouch to bypass the proximal segment (the part of the intestine closest to the stomach) (Figure 5C). This not only restricts food and caloric intake, but also decreases the amount of small intestine available for nutrient absorption.

Numerous reviews of bariatric surgery outcomes report that substantial and sustained weight loss can be achieved following surgery in most study patients.^10-13 Further, a majority of bariatric surgery patients experience complete resolution of many weight-related comorbidities, including diabetes, hypertension, hyperlipidemia, and obstructive sleep apnea. Patients have also reported improvements in their quality of life, especially in aspects such as depression, functional status, and self-esteem.

However, surgery is not without risk. A small number of patients do not experience sustained weight loss. While most patients have few problems related to surgery, nearly 10% are readmitted to the hospital in the period following the procedure. Risks of two complications after surgery are shown in Figure 6. A small number of patients (3-5%) experience infection at the surgical site; many of these patients will need another surgical procedure. Mortality after bariatric surgery is very low, occurring on average in 1 out of 300 patients. Helping patients to understand these risks—especially the uncommonly low ones—is a major goal of the visual display in Figure 6.

Figure 6.

Risks of complications from bariatric surgery.

Reaching the right decision

Bariatric surgery is not always the best choice for treating obesity. Some patients do not feel that their weight is a problem or may not want to take steps to lose weight. Some patients prefer medical therapy and are successful in maintaining their weight loss. For other patients, their expectations of improvement in physical or emotional health resulting from surgery may not be realistic, or their concurrent medical problems may increase the risk of death or another adverse outcome. Bariatric surgery programs and insurers usually require that patients undergo a supervised course of medical therapy before considering surgery. Physical and psychological screenings are also necessary, and some programs require that patients take a knowledge exam to demonstrate that they understand the likely benefits and possible risks. The latter is particularly important because most bariatric surgery patients have a poor understanding of the outcomes.

When bariatric surgery is medically appropriate, the next question is whether it is the right choice for a patient. Arriving at an informed, high-quality decision involves three requirements: 1) the patient receives balanced information in a format that is understandable; 2) the patient has the opportunity to clarify his or her values and preferences related to the options; and 3) the patient is invited into the decision-making process. Together, this process is known as shared decision-making and is often facilitated by decision aids.

A growing body of literature, including numerous publications from the Dartmouth Institute of Health Policy and Clinical Practice, supports the use of decision aids and shared decision-making for preference-sensitive surgical decisions.^14,15 The decision faced by morbidly obese patients considering elective bariatric surgery is complex and must take into account numerous factors: patient preferences, procedure characteristics, surgical risks, surgeon experience, insurance coverage, and potential for success. Given this complexity, patients can easily become overwhelmed with information. As a result, decision support tools are ideally suited for patients considering bariatric surgery. Previous evaluations of decision aids in this population have reported significant improvements in knowledge, value concordance, decisional conflict, decisional self-efficacy, and treatment choice.¹⁶ Decision aids typically provide a broad range of information to patients, including discussion of potential treatment options (diet-based, medical therapies, and surgical treatments), and offer shared decision-making as a tool to improve decision quality.

The Michigan Bariatric Surgery Collaborative (MBSC) is also developing a new decision support tool for the treatment of morbid obesity. The tool will be continuously updated by registry data to ensure that information about procedures, as well as patient-specific data regarding risks and benefits, are accurate and current (Figure 7). This will allow patients to make personalized treatment decisions that are better informed by the latest evidence and more congruent with their individual preferences. The tool will be disseminated throughout the state and will be rigorously studied to evaluate both clinical effectiveness and subjective patient experience. If proven effective, it will be made available nationally so that organizations may use this experience as a blueprint to develop similar decision support tools for other preference-sensitive conditions.

Figure 7.

Conceptual model for novel bariatric surgery decision support tool. To learn more about the Michigan Bariatric Surgery Collaborative initiative, please visit www.mbscsurgery.org.

Choosing surgical care, and the type of surgical care

The patient and his or her physician must choose not only whether or not to proceed with surgery, but also the specific procedure that is best for the patient. Procedure choice is influenced by several factors: the patient’s preferences, procedure availability, insurance coverage, the surgeon’s preference, and the current evidence regarding a procedure’s clinical effectiveness. The risk of complications and potential for weight loss also differ with each procedure and change over time. As outcomes research has developed, information about surgical outcomes has become essential to inform patient and provider preferences. Historic and current trends in bariatric procedure utilization reflect the evolution of these factors.

Trends in utilization

The rise in rates of obesity, along with increasing interest in surgical options, has resulted in a dramatic increase in utilization of bariatric surgery in recent years. Figure 8 illustrates the increasing utilization of bariatric surgery from 2001 to 2011. The national average rate of bariatric surgery increased nearly sixfold between 1990 and 2000, and this rise has continued through 2011.^17,18 Moreover, the shift in surgical approach from more invasive open procedures (more than 85% of all bariatric surgery in 2000) to a less invasive laparoscopic approach (more than 90% of all bariatric surgery in 2008) over the decade led to a further striking increase in utilization. Rates of overall procedure use reached a high of nearly 40 per 100,000 Medicare patients in 2009.¹⁹

Figure 8.

Bariatric surgery utilization trends among Medicare beneficiaries (2001-11).

The choice of procedure also shifted during this 20-year period. As gastric bypass gained popularity, increasing from 55% of all bariatric procedures in 1990 to 99% in 2003, vertical banded gastroplasty fell out of favor, decreasing from more than 40% to 7% during the same period.^18-20

Additional changes in utilization during this decade reflected emerging research in support of novel procedures and the policy changes that followed. The Food and Drug Administration approved adjustable gastric banding for use in the United States in 2001 following multiple reports of successful outcomes in Europe and Australia.^21,22 In the ensuing years, utilization of adjustable gastric banding grew substantially due to its ease of reversibility, adjustability, and overall safety profile.^23-25

Policy influence on procedure utilization

Based on the growing body of literature supporting bariatric surgery as a treatment for morbidly obese patients, the Centers for Medicare & Medicaid Services (CMS) announced in 2006 that gastric bypass, laparoscopic adjustable gastric banding, and biliopancreatic diversion with duodenal switch would be covered for Medicare patients meeting certain criteria.²⁶ Though overall rates of bariatric surgery had started to decline after 2004, this expansion of coverage increased the availability and use of these procedures. Between 2005 and 2010, as the popularity of adjustable gastric banding grew, the relative utilization of gastric bypass slowly decreased. In 2008, laparoscopic gastric bypass accounted for 69% of all bariatric procedures, while laparoscopic adjustable gastric banding accounted for 29%.¹⁹

Laparoscopic sleeve gastrectomy was introduced to the field in 2003. Select private insurers began to cover the procedure in the years following, although CMS chose not to cover the procedure until 2006. This increased insurance coverage was followed by the rise in utilization observed in Figure 8. During this same period, new research on adjustable gastric banding reported increased late complications and high long-term failure rates (poor weight loss and band removal),^27,28 and consequently, utilization of adjustable gastric banding decreased.

Geographic variation in bariatric procedure utilization is indicative of the complexity of the decision faced by morbidly obese patients. Rates of bariatric surgery varied by a factor of more than twenty during the period from 2007 to 2011, from fewer than 9 procedures per 100,000 Medicare beneficiaries in San Francisco (4.0), San Mateo County (7.9), and Santa Rosa, California (8.4) to more than 80 per 100,000 in Muskegon, Michigan (110.9) and Kettering, Ohio (83.7) (Figure 9). In general, rates of bariatric surgery were higher in the Midwest and northwestern regions than in the southern states (Map 4). The national average rate of bariatric surgery during the period from 2007 to 2011 was 32.8 per 100,000 enrollees.

Figure 9.

Bariatric surgery among 100,000 Medicare beneficiaries among hospital referral regions (2007-11). Each blue dot represents the rate of bariatric surgery in one of 306 hospital referral regions in the U.S. Red dots indicate the regions with the 5 lowest (more...)

Map 4.

Bariatric surgery among 100,000 Medicare beneficiaries (2007-11). Rates are adjusted for age, sex, and race.

Figure 10 shows a hospital referral region’s rates of obesity (Figure 10A) or diabetes (Figure 10B) on the horizontal axis, while the vertical axis shows the same region’s rate of bariatric surgical procedures. Regional rates of obesity and diabetes have virtually no relationship to the rates of bariatric surgery (R² = 0.03 and 0.01, respectively). Rather, differences in procedure characteristics, safety profiles, and the evidence supporting clinical effectiveness each contribute to these variations. Provider preferences, reflecting their training and experiences, are also a major contributor. Given the lack of shared decision-making in most health systems, it is hard to argue that patient preferences are a dominant cause of regional variation in utilization.

Figure 10A.

Relationship between obesity rates and bariatric surgery among hospital referral regions. Each dot represents one of the 306 hospital referral regions across the United States. Regional rates of obesity and diabetes were unrelated to rates of bariatric (more...)

Figure 10B.

Relationship between type II diabetes and bariatric surgery among hospital referral regions. Each dot represents one of the 306 hospital referral regions across the United States. Regional rates of obesity and diabetes were unrelated to rates of bariatric (more...)

The notion that surgery might be an effective population-based solution for obesity should be met with some skepticism. Given the Centers for Disease Control and Prevention (CDC) estimates for 2010, more than 10 million Americans are extremely obese, to the extent that their obesity would exceed body mass index (BMI) criteria for bariatric surgery (BMI > 40). However, in 2010, fewer than 150,000 bariatric surgical procedures were performed in the United States, suggesting that an eighty-fold increase in the number of bariatric procedures would be needed to “treat” obesity surgically in the U.S., at a cost that would exceed $17 billion (based on an average Medicare payment of $1,700 for a single bariatric procedure). These estimates are decidedly conservative, as they only include the payments made to surgeons for the procedure. Even under a conservative assumption wherein only 10% of eligible obese Americans—about 1 million people—were ultimately treated with bariatric surgery, payments to hospitals, surgical centers, and physicians could potentially exceed $15 billion.

Using regional collaboratives to study comparative effectiveness

Our knowledge about the relative effectiveness of different bariatric procedures is incomplete. For example, randomized trials comparing gastric bypass to sleeve gastrectomy are limited to small, single-center studies with short follow-up intervals, and the results may not apply to the general obese population.^29-36 Most large observational studies utilize administrative data limited to perioperative periods, examine nonspecific surgical outcomes, and often lag behind current practice. Observational studies with longer follow-up periods—that report detailed bariatric surgery-specific clinical risk factors and outcomes—are usually single-center studies. As a result, uncertainty remains regarding the outcomes associated with certain patients. Within the state of Michigan, however, a unique environment exists to allow for more detailed evaluation of these issues.

The Michigan Bariatric Surgery Collaborative (MBSC), formed in 2006, is a voluntary regional consortium of all surgeons who perform bariatric surgery and the hospitals where it is performed within the state. The timely collection and distribution of MBSC data—along with detailed bariatric-specific risk factors and outcomes—allows for a more accurate understanding of current trends in the utilization, safety, and effectiveness of bariatric procedures. For example, trends in procedure utilization in Michigan over time parallel those seen nationally. Figure 11 illustrates the utilization of gastric bypass, adjustable gastric banding, and sleeve gastrectomy in Michigan during the period from 2006 to 2012. In 2006, gastric bypass accounted for 61% of all bariatric surgery in the state, and adjustable gastric banding accounted for 37%. Utilization of sleeve gastrectomy began in 2007 and increased rapidly in the ensuing years, while rates of gastric bypass decreased moderately and rates of adjustable gastric banding decreased substantially. In 2012, 45% of bariatric procedures performed in Michigan were sleeve gastrectomies, while 43% were gastric bypasses, and only 11% were adjustable gastric banding procedures.

Figure 11.

Trends in utilization of gastric bypass, adjustable gastric banding, and sleeve gastrectomy in Michigan (2006-12). BPD/DS = biliopancreatic diversion with duodenal switch. AGB = adjustable gastric banding. RYBG = Roux-en-Y gastric bypass.

Technical quality: the role of centers of excellence in bariatric surgery

Ensuring safe, high-quality bariatric surgical care became a public health priority as utilization increased dramatically during the 2000s. Initial studies of the modern bariatric surgical experience reported varying mortality rates across hospitals and surgeons. A meta-analysis of case series and early population-based analyses of administrative data reported 30-day mortality rates between 0.2 and 1.9%,^10,20,37,38 while examination of Medicare patients revealed mortality rates of 2.0% at 30 days and 4.6% at 1 year.³⁹ Many of these studies linked surgeon and hospital volume to surgical outcomes: “low-volume” centers exhibited two to threefold increased odds of mortality, and this effect was most pronounced in older, high-risk patients.^40,41

Consequently, the American Society for Bariatric Surgery established a “centers of excellence” program in 2003 to implement national standards for institutions performing bariatric surgery.^42,43 A similar program was developed by the American College of Surgeons.⁴⁴ When CMS issued its national coverage decision in 2006, the criteria limited coverage to certified centers of excellence only.²⁶ However, subsequent research evaluating the effect of the CMS policy on bariatric surgical outcomes revealed mixed results. Several studies evaluating centers of excellence compared to other hospitals failed to identify improvements in outcomes, despite increased hospital volumes at centers of excellence.^45,46 One such study found that rates of serious complications varied widely regardless of the “center of excellence” designation. In contrast, multiple studies examining outcomes in Medicare patients before and after the CMS policy revealed beneficial effects: 90-day mortality, complications, readmissions, and length of stay were all reported to decrease following the restriction of coverage.^47,48 However, these studies could not distinguish the effect of the policy from general trends toward improved outcomes during the study period.

To clarify these conflicting studies, Dimick and colleagues used hospital discharge data to evaluate the effect of the CMS policy on Medicare patients undergoing bariatric surgery compared to a control group of non-Medicare patients. To isolate improvements in outcomes after the coverage decision from coincident temporal trends, the authors applied an econometric technique—difference-in-differences— commonly used to evaluate the effect of policy changes. This evaluation determined that, after controlling for temporal trends, there was no benefit to the coverage restriction.⁴⁹ Following the CMS policy, rates of any complication, serious complications, and reoperation decreased substantially in both Medicare and non-Medicare patients, but trends toward improved outcomes were present in both groups well before the policy was implemented (Figure 12). Difference-in-differences analysis failed to reveal an independent effect of the CMS policy.

Figure 12.

Trends in adverse outcomes before and after the implementation of the Centers for Medicare & Medicaid Services bariatric surgery national coverage decision. Each data marker represents two quarters within each year. The national policy restricting (more...)

Though this evaluation failed to identify a benefit of the CMS policy, subsequent analyses demonstrated restrictions to access, particularly among minority beneficiaries.⁵⁰ While rates of bariatric surgery remained stable among non-Medicare minorities, rates in Medicare minority patients declined by 17% after the February 2006 national coverage decision. Publication of these findings had a substantial impact on CMS policy. In September of 2013, CMS decided to eliminate the “facility certification requirement,” allowing beneficiaries fulfilling appropriate criteria to pursue bariatric surgery at the institution of their choice.^51,52

These examples of policy change clearly illustrate the importance of outcomes research to the field of bariatric surgery. Patients and providers have all benefited from the ongoing evaluation of bariatric surgical quality and access to care. Future health services research must build on these successes through continued evaluation of current techniques, surgical outcomes, systems of care, and health policy.

Spending on surgery – or spending on prevention?

Nationally, health care costs related to bariatric surgery were estimated at just under a billion dollars in 2002 and had grown to nearly $3 billion by 2011. While the surgical treatment of obesity is efficacious, this clinical effectiveness comes at a relatively steep price, and extrapolation of this treatment to the true “epidemic” of obesity would come at an impractical and implausible cost.

Should we spend our efforts—and financial resources—on alternatives to surgery for patients with obesity? Progress has been made in preventing childhood obesity; a recent CDC report showed that childhood obesity rates declined in 19 of the 43 states where obesity prevention programs were introduced.⁵³ Many might argue that directing some of the resources currently allocated to surgical care toward preventing childhood obesity might have more impact. How resources are—or should be—allocated between preventive measures aimed at younger obese Americans and surgical treatment of older patients remains an open question.

Using quality improvement to limit variation

While the examples above illustrate improved outcomes for patients undergoing bariatric surgery—and the vital role health services research has played—opportunities for continued improvement exist. Wide variations persist in hospital processes, surgical outcomes, and procedure utilization despite these improvements. Patients considering bariatric surgery are faced with complex decisions and can become overloaded with information. In addition to these issues, current health care reform efforts require providers at all levels to increase quality of care while simultaneously decreasing costs. Going forward, there is no doubt that health services research will be essential to continued improvements in outcomes and quality.

Within the Michigan Bariatric Surgery Collaborative (MBSC), research is currently under way to better understand these challenges and develop novel strategies for quality improvement. Numerous publications have highlighted the benefits of regional quality collaboratives.^46,54-57 Collaboratives have been shown to lead to decreased complications, mortality, resource utilization, and costs. For bariatric surgery, the MBSC provides an example of the success that can be achieved through regional quality collaboratives: the standardization of venous thromboembolism (VTE) prophylaxis in MBSC hospitals.⁵⁸ After evaluation of VTE prophylaxis regimens revealed wide variations across MBSC hospitals in 2008, the collaborative used registry data to develop a VTE risk-prediction tool and identify optimal prophylaxis strategies for each risk cohort. This and other examples illustrate how further improvements for bariatric surgery patients can be achieved on a national scale.

Decision aids and shared decision-making

As described previously, decision support tools can be valuable aids for patients considering bariatric surgery. The MBSC’s work developing a new decision support tool for the treatment of morbid obesity (Figure 7) will allow patients to make personalized treatment decisions that are better informed by the current evidence and more congruent with their individual preferences.