When traditional approaches for weight loss, such as diet, exercise, and medications, fail as effective treatments for obesity, bariatric surgical procedures that restrict stomach size or lead to altered absorption of nutrients may be performed. While these procedures often result in significant, sustained weight loss, the benefits must be balanced against the short- and long-term risks of bariatric surgery. The Longitudinal Assessment of Bariatric Surgery (LABS) observational study was established by the LABS Consortium to assess the risks and health benefits associated with bariatric surgery and to identify aspects of the procedures and patient characteristics associated with optimal outcomes. The study is organized into three phases: LABS-1, which evaluates the short-term safety of bariatric surgery; LABS-2, which evaluates the longer-term safety and efficacy of bariatric surgery, in addition to examining patient characteristics associated with short- and intermediate-term outcomes; and LABS-3, which examines the psychosocial, quality-of-life, and health economics aspects of obesity, as well as the mechanisms of obesity-related diseases.

The LABS-1 study enrolled patients at least 18 years of age who underwent bariatric surgical procedures between March 2005 and December 2007 at LABS surgical centers. Participants underwent a pre-operative evaluation, during which data was collected on height, weight, blood pressure, comorbid conditions, and physical examination. Participant outcomes were recorded post-operatively. The primary outcome measure was a composite endpoint of any of the following occurring within 30 days of surgery: death; deep vein thrombosis (DVT) or venothromboembolism (VTE); reintervention using percutaneous, endoscopic, or operative techniques; or failure to discharge from the hospital. Of the 4776 patients who had a first-time procedure, over half had at least two co-morbid conditions. The 30-day mortality rate for Roux-en-y gastric bypass or laparoscopic adjustable gastric banding was 0.3%; 4.3% of participants had at least one major adverse outcome. The LABS-1 study showed that the short-term risk of death and adverse outcome after bariatric surgery was low, particularly when contrasted with patient characteristics.

Following conclusion of the LABS-1 study, the LABS-2 study was initiated to examine the longer-term safety, outcomes, and durability of health changes of bariatric surgery. The primary objectives of the LABS-2 study were to determine weight, medical, surgical, and behavioral outcomes, including incidence and remission of co-morbid conditions, and to evaluate patient, procedure, and other characteristics that were associated with these outcomes. The cohort included patients who underwent bariatric surgery at LABS clinical centers through 2009.

Clinical assessments and detailed interviews and questionnaires are administered at several post-operative time points (30 days, 6 months, 12 months following surgery, and annually thereafter) to assess risks of surgery and changes in clinical, metabolic, and psychosocial characteristics in patients following bariatric surgery. Detailed data about the surgical procedure and peri- and post-operative care are also collected to determine if components of the surgical procedure, care, and/or clinical/demographic patient characteristics are associated with post-operative risks and changes in patient status.

An ancillary study from LABS-2 regarding psychosocial issues associated with weight loss was conducted at two of the LABS study centers, and a set of control participants were recruited from primary care practices outside of the LABS consortium. The overall duration of this ancillary study was 48 months with the goal of assessing changes in sexual function and sex hormones in the two groups at predetermined follow-up visits.

An ancillary study from LABS-3 regarding psychosocial issues associated with bariatric surgery was conducted at three of the LABS study centers with participants that were previously enrolled in LABS-1 and LABS-2. This prospective cohort ancillary study aimed to understand the mental health impacts of bariatric surgery and changes in mental health outcomes over a 7-year follow-up period. Data were collected on psychosocial issues such as eating disorders, substance abuse, affective disorders, and cognitive function.

The current data package available includes full data from LABS-1 and LABS-2, and ancillary data from LABS-2 and LABS-3.

The primary objective of the LABS observational study is to assess the risks and health benefits associated with bariatric surgery and to identify aspects of the procedures and patient characteristics associated with optimal outcomes.

Patient and procedure characteristics are correlated with short- and long-term outcomes of bariatric surgery to evaluate the safety and efficacy of bariatric surgical procedures as treatment for patients with obesity and to identify risk factors. Additionally, changes in medical and psychosocial measures can impact the outcomes of bariatric surgery over time.

Individuals at least 18 years of age who underwent a first-time bariatric surgical procedure at LABS clinical centers were enrolled in the study. The LABS-1 cohort includes patients who underwent surgery between March 2005 and December 2007; the LABS-2 cohort includes patients who underwent surgery through April 2009. The LABS-2 ancillary study cohort includes patients who were previously enrolled in LABS-2, and the LABS-3 ancillary study cohort includes patients who were previously enrolled in LABS-1 and LABS-2.

Of the 4776 patients enrolled in the LABS-1 study who had a first-time procedure, over half had at least two co-morbid conditions. The 30-day mortality rate for Roux-en-y gastric bypass or laparoscopic adjustable gastric banding was 0.3%; 4.3% of participants had at least one major adverse outcome. The LABS-1 study showed that the short-term risk of death and adverse outcome after bariatric surgery was low, particularly when contrasted with patient characteristics.

Initial findings of the LABS-2 study show that patients with severe obesity who underwent bariatric surgery experienced substantial weight loss 3 years following the surgical procedure, with the majority experiencing maximum weight change during the first year. The amount and trends of weight loss, diabetes, blood pressure, and lipid levels were variable. Follow-up of the LABS-2 and LABS-3 cohorts are ongoing.

The LABS-2 ancillary study found that for men enrolled that had bariatric surgery and lost one-third of their weight had experienced a significant increase in total testosterone, but no improvements in sexual function or relationship satisfaction. For women enrolled that had bariatric surgery, there were significant improvements in sexual functioning, sex hormones, and overall psychosocial status.

The LABS-3 ancillary study found that prevalence of any mental disorder was lower at years 4 and 5 post-surgery but not at 7 years. In addition, having a concurrent mood disorder was associated with greater weight gain post-surgery within the cohort. Other relationships between eating disorders, mental health, cognitive function, and bariatric surgery were variable.