Patients with obesity and the severest form of type 2 diabetes can have their diabetes improved or put into remission by bariatric surgery leading to substantial cost savings for the NHS, according to a large-scale collaborative study between the British Obesity and Metabolic Surgery Society (BOMSS) and the Population Health Research Institute at St Georges, University of London. The findings, ‘Bariatric surgery for patients with type 2 diabetes mellitus requiring insulin: Clinical outcome and cost-effectiveness analyses’, were published in PLOS Medicine. Treating T2DM and its complications is estimated to cost the NHS £10 billion every year.
“Patients with obesity and severe diabetes have not previously been prioritised for surgery, but our findings suggest that offering weight loss surgery to this group of patients not only leads to improved health, but by reducing the need for multiple daily medications, benefits the taxpayer,” said Mr Omar Khan, bariatric surgeon and lead author of the study from St George’s, University of London, UK.
Although each bariatric operation costs the NHS approximately £6,000, the researchers found that this figure was less than the costs for medications to treat their type 2 diabetes. When costs of avoiding the complications of diabetes were also considered, the average patient treated with surgery was expected to save the NHS £4,229 over a five-year timeframe.
For the study, the investigators sought to examine the effects of surgery on patients with more advanced type 2 diabetes (i.e. those who require insulin injections) who have a higher chance of developing diabetes complications including: blindness, limb amputation and heart disease. They used data from the UK’s National Bariatric Surgical Registry (a bespoke database for the prospective collection of demographic, perioperative, and clinical outcome data for patients with obesity undergoing bariatric surgery in the UK and Republic of Ireland) to analyse the outcomes of nearly 2,000 patients living with obesity and type 2 diabetes requiring insulin who had surgery between 2009 and 2017.
Diabetes status in NBSR is recorded preoperatively and at every postoperative visit as follows: no indication of T2DM; impaired glycaemia or impaired glucose tolerance (diet controlled); oral hypoglycaemics only; or insulin treatment (insulin with or without additional hypoglycaemic medications). As insulin use has consistently been identified as a strong negative predictor of remission of T2DM after bariatric surgery, they focused on patients that were using insulin for T2DM preoperatively.
The outcomes for this group were combined with data sourced from a comprehensive literature review to develop a state-transition microsimulation model to evaluate cost-effectiveness of bariatric surgery versus best medical therapy (BMT) for patients over a five-year time horizon. The main outcome measure for the clinical study was insulin cessation at one-year post-surgery including age, initial body mass index (BMI), duration of T2DM and weight loss. The main outcome measures for the economic evaluation were total costs, total quality-adjusted life years (QALYs) and incremental cost-effectiveness ratio (ICER) at willingness-to-pay threshold of GBP£20,000.
The researchers identified 3,261 patients with T2DM and who were taking insulin for the analysis, and had undergone primary Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG) or adjustable gastric band (AGB) between January 2009 and May 2017. Of these, 2,484 (76.2%) had at least one follow-up visit recorded in the NSBR, with 1,847 having one visit between six- and 24-months post-surgery. Of these, 1,313 (71.1%) underwent RYGB, 397 (21.5%) SG and 137 (7.4%) AGB.
At one-year follow-up (mean of 355 days post-procedure), the mean percentage weight loss was 27.4%, with evidence of differential weight loss between surgical groups (p<0.001). Approximately one-third (32.7%) of the total cohort were still using insulin at one year, with another third (33.5%) no longer recorded as having T2DM. There was significant variation in T2DM status by procedure (p<0.001); with 33.6% having ceased use of insulin in the AGB group compared to 64.5% and 71.7% in the SG and RYGB groups, respectively, and a smaller proportion of patients assessed as having no indication of T2DM following AGB (5.1%) than SG and RYGB (30.0% and 37.6%, respectively).
Follow-up of over two years was available for 857 patients, of whom 605 (70.6%) underwent RYGB, 156 (18.2%) SG, and 96 (11.2%) AGB. Again, weight loss again varied by procedure (p<0.001) with levels similar to those reported at one-year follow-up. For diabetes status, differences between procedures were still apparent (p<0.001), with a wider gap now seen between the percentage of patients with no indication of T2DM in the RYGB (42.2%) and SG (26.9%) groups.
They also reported that prevalence of insulin use reached a plateau at around 19 to 24 months, stabilising at this level up to four years after surgery, with BMI reaching a plateau at around 13 to 18 months, stabilising over the next 4 years.
Insulin cessation was more prevalent in patients undergoing RYGB compared to SG (p=0.02) or AGB (p<0.001). Male patients were more likely to cease insulin use after surgery (p<0.001). There was no evidence of different insulin cessation rates by number of comorbidities. Furthermore, patients with shorter T2DM duration were more likely to cease insulin (p<0.001, for patients with duration <5 years as compared to those with duration >10 years). When adjusted for other baseline demographic factors - procedure, gender and duration of diabetes were all independent predictors of cessation of insulin use after surgery (p<0.001).
Once weight loss was adjusted for using either model, SG was no longer associated with statistically inferior rates of insulin cessation compared to RYGB, unsurprisingly, AGB was still associated with poorer rates of insulin cessation than RYGB (p<0.001).
Costs directly attributable to adverse events of treatment (i.e., in the surgical arm costs of surgical complications plus adverse drug reactions; and in the BMT group the adverse drug reactions), the cumulative costs for the bariatric surgical group were GBP£1,152, and for the group undergoing BMT, GBP£955. This represents an incremental difference of GBP£197 in favour of BMT over a five-year period.
Based on the assumptions of the effects of BMT and bariatric surgery on modifying HbA1c and BMI, bariatric surgery leads to a lower cumulative incidence of diabetes-related complications and consequently lower cost for the management of these complications.
The costs of surgery are incurred at the start of the model and not spread over the five-year period; hence, at approximately 3.5 years after surgery, the total cost of a patient treated with bariatric surgery equals the total cost of a patient treated with BMT, whereby from that breakeven point, bariatric surgery becomes the cost-saving option. In summary, bariatric surgery is predicted to result in a total cost saving of GBP£4,229 when compared to BMT over a five-year time period.
The authors report that probabilistic sensitivity analysis demonstrated that bariatric surgery consistently leads to cost savings when compared with BMT and in more than 50% of cases to positive incremental health benefits.
“While previous economic analyses have suggested that a surgical strategy for T2DM provides clinical benefits but with higher up-front cost to the healthcare payer, this study indicates that for patients with T2DM requiring insulin, the total cost to the health payer is reduced following bariatric surgery as compared to best medical therapy over a five-year time period,” they concluded. “This pattern is seen even when the clinical benefits of bariatric surgery over best medical therapy, in terms of avoidance of future complications, are not considered.”
“This study strengthens existing evidence that bariatric surgery can help some people with obesity and insulin-treated type 2 diabetes to go into remission, and in turn, that this approach can save the NHS vital funds compared to the best alternative non-surgical treatments,” said Nikki Joule, Policy Manager at Diabetes UK. “Despite the known clinical benefits of bariatric surgery for type 2 diabetes, we know that people who meet the current NHS criteria are often not offered this treatment. We urge the NHS to take action to increase the provision and take-up of bariatric surgery so that more people have the chance of putting their type 2 diabetes into remission.”
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