The evaluation of clinical outcomes of a pre-bariatric surgery medical weight management programme

Background: 

Obesity is a public health challenge; in the UK, 24% of adults are known to be obese. Obesity may lead to complications including type 2 diabetes mellitus, ischaemic heart disease (IHD), obstructive sleep apnoea syndrome (OSAS), and certain psychological
disorders. Bariatric surgery is known to be very effective for weight reduction and for reducing the risk of developing obesity-associated complications. A study found that the use of medical weight management services that focus on helping bariatric patients make lifestyle changes, in addition to bariatric surgery is more effective for weight reduction than bariatric surgery alone. Therefore, a tiered, weight management service model was designed by the National Institute for Health and Care Excellence to aid lifestyle changes in patients who are obese, such as modifications in diet, exercise, and behaviour. Tier-3 services were designed to facilitate such changes with appropriate multidisciplinary specialist input, and are a prerequisite for progressing to bariatric surgery in the UK. It screens for and manages medical causes of obesity such as endocrine disorders and OSAS. Currently, there is a paucity of
published evidence of evaluation of tier-3 services.

The STOP-BANG questionnaire is a screening tool for OSAS, consisting of eight dichotomous items. The likelihood of a patient suffering from moderate-severe OSAS, with a STOP BANG score of <3 and <5, is 25% and 45%, respectively. There is much dispute about what the cutoff score should be, to diagnose OSAS.

Aims: 
The aim was to investigate the clinical outcomes (as measures of physical and mental health) of patients who use a regional tier-3 bariatric service that caters for a population of approximately 300,000 people. The effectiveness of using the STOP-BANG questionnaire for diagnosing OSAS was also evaluated.

Methodology: 
This retrospective cohort study included 234 patients who used tier-3 services, between April 2013 and January 2017. The BMI, weight, total cholesterol, and HbA1c were compared, before and after tier-3 service usage. The STOP BANG questionnaire scores and information regarding the need for continuous positive airway pressure (CPAP) therapy for OSAS were also analysed. 

We compared psychometric measures before and after cognitive behavioural therapy (CBT) for patients referred to the bariatric psychologist. There were three validated instruments used to evaluate the response to CBT. The patient health questionnaire (PHQ9) and CORE-10 measures test for depression severity and any associated symptoms. The weight efficacy lifestyle (WEL) questionnaire assesses how well patients resist unhealthy eating.

Results
There were significant reductions in mean BMI, weight, HbA1c, and total cholesterol by 3.66%, 3.58%, 9.05% and 8.75% respectively, following tier-3 service usage. Out of 84 patients that had a STOP BANG score t3, 47.62% of them were administered CPAP
therapy. There were significant improvements in the psychometric measures, with a decrease of 7.8 and 6.71, for the mean PHQ-9 and CORE-10 scores respectively, and an increase in the mean WEL scores by 2.29, following CBT.

Discussion
This study suggests that the STOP BANG questionnaire is suitable for screening for OSAS. However, there is insufficient evidence to conclude what the ideal cut off score should be, to be considered a positive test. This tier-3 bariatric service has improved the clinical outcomes of service users, in terms of physical and mental health. This study emphasises that comprehensive medical interventions, especially those that focus on lifestyle changes can significantly reduce the rates of obesity and its associated complications and highlights its importance prior to referral for bariatric surgery.