Background
Bariatric surgery is a common procedure worldwide for the treatment of severe obesity and associated comorbid conditions but there is a lack of evidence as to medium-term safety and effectiveness outcomes in a United Kingdom setting. Objective To establish the clinical outcomes and adverse events of different bariatric surgical procedures, their impact on quality of life and the effect on comorbidities. Design Prospective observational cohort study. Setting National Health Service secondary care and private practice in Scotland, United Kingdom. Participants Adults (age >16 years) undergoing their first bariatric surgery procedure. Main outcome measures Change in weight, hospital length of stay, readmission and reoperation rate, mortality, diabetes outcomes (HbA1c, medications), quality of life, anxiety, depression. Data sources Patient-reported outcome measures, hospital records, national electronic health records (Scottish Morbidity Record 01, Scottish Care Information Diabetes, National Records Scotland, Prescription Information System). Results Between December 2013 and February 2017, 548 eligible patients were approached and 445 participants were enrolled in the study. Of those, 335 had bariatric surgery and 1 withdrew from the study. Mean age was 46.0 (9.2) years, 74.7% were female and the median body mass index was 46.4 (42.4; 52.0) kg/m2. Weight was available for 128 participants at 3 years: mean change was −19.0% (±14.1) from the operation and −24.2% (±12.8) from the start of the preoperative weight-management programme. One hundred and thirty-nine (41.4%) participants were readmitted to hospital in the same or subsequent 35 months post surgery, 18 (5.4% of the operated cohort) had a reoperation or procedure considered to be related to bariatric surgery gastrointestinal complications or revisions. Fewer than five participants (<2%) died during follow-up. HbA1c was available for 93/182 and diabetes medications for 139/182 participants who had type 2 diabetes prior to surgery; HbA1c mean change was −5.72 (±16.71) (p = 0.001) mmol/mol and 65.5% required no diabetes medications (p < 0.001) at 3 years post surgery. Physical quality of life, available for 101/335 participants, improved in the 3 years post surgery, mean change in Rand 12-item Short Form Survey physical component score 8.32 (±8.95) (p < 0.001); however, there was no change in the prevalence of anxiety or depression. Limitations Due to low numbers of bariatric surgery procedures in Scotland, recruitment was stopped before achieving the intended 2000 participants and follow-up was reduced from 10 years to 3 years. Conclusions Bariatric surgery is a safe and effective treatment for obesity. Patients in Scotland, UK, appear to be older and have higher body mass than international comparators, which may be due to the small number of procedures performed. Future work Intervention studies are required to identify the optimal pre- and post surgery pathway to maximise safety and cost-effectiveness. Study registration This study is registered as ISRCTN47072588. Funding details This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 10/42/02) and is published in full in Health Technology Assessment; Vol. 28, No. 7. See the NIHR Funding and Awards website for further award information.