A Simple Prediction Rule for All-Cause Mortality in Bariatric Surgery Eligible Patients

sharma-obesity-blood-sugar-testing2Regular readers will be quite familiar with our previous work on the Edmonton Obesity Staging System (EOSS), which ranks bariatric patients on a five-point ordinal scale based on the presence and severity of functional, mental and medical health problems.

As we showed in our analyses of several large datasets, individuals at higher EOSS stages are at far greater risk of all-cause mortality than individuals at lower EOSS stages. Interestingly enough, we found that BMI levels contribute little, if anything, to the actual mortality risk of these individuals – apparently, all that counts is how “sick” you are, not how “big” you are.

While EOSS is gradually winding its way around the globe towards greater popularity and acceptance, my colleagues and I now publish an even simpler rule for predicting all-cause mortality in bariatric patients – the paper was just released online at JAMA-Surgery.

In this paper, we studied over 15,000 individuals from the United Kingdom General Practice Research Database (GPRD), a population-representative primary care registry, who met current eligibility criteria for bariatric surgery (BMI, ≥35.0 alone or 30.0-34.9 with an obesity-related comorbidity) between January 1, 1988, through December 31, 1998.

We used binary logistic regression to construct a parsimonious model and a clinical prediction rule for 10-year all-cause mortality.

The final model, which included age, type 2 diabetes mellitus, current smoking, and male sex had a concordance or C-statistic of 0.768.

Based on this model, we developed a simply clinical prediction rule, scoring into 4 tiers with 10-year all-cause mortality ranging from was 0.2% in tier 1 to5.2% in tier 4.

Although BMI significantly (albeit poorly) predicted mortality, it did not add much to the model in terms of discrimination or calibration.

Thus, our findings show that all-cause 10-year mortality in obese individuals eligible for bariatric surgery can be estimated using a simple 4-variable prediction rule based on age, sex, smoking, and diabetes mellitus.

Once again (as in EOSS), body mass index was not an important mortality predictor.

These findings may have important consequences for prioritization of patients for bariatric surgery, at least if one chooses to prioritize individuals with the highest mortality risk – these would be older men with type 2 diabetes, who smoke (whereby, one would assume that they would immediately stop smoking if nothing else).

However, we also realize that mortality risk is only one consideration that goes into deciding who will benefit the most from surgery.

Certainly, severe obesity is associated with numerous other important consequences on mental, physical and economic health, which, although not lethal, can well make life quite unpleasant. The positive impact of bariatric surgery on these problems is well documented and probably as (if not more) important to people living with obesity than simply staying alive.

Nevertheless, to clinicians and administrators the message is clear – BMI alone is not a good predictor of health and certainly not a predictor of mortality. Prioritization systems based on BMI should be abandoned.

You can estimate your own 10-year all-cause mortality risk here.

Montreal, QC


Post-Surgery Weight Regain: Roux-en-Y Gastric Bypass

rouxeny-gastric-bypassTo conclude this series of posts on our systematic review of weight regain following bariatric surgery, published in Obesity Surgery, we know turn to the ‘technical’ reasons for weight regain following Roux-en-Y gastric bypass (RYGB).

As with gastric banding and sleeve gastrectomy, enlargement of the gastric pouch can lead to weight regain.

In addition, the connection between the stomach and small intestine (gastrojejunostomy or stoma) can dilate allowing easier passage of food into the small intestine. According to the reports in the literature, stomal dilation is one of the
most frequently identified “technical” abnormalities in patients experiencing weight regain and has been shown to be independently associated with weight recidivism and to occur as early as 6 months following surgery.

Other studies have found a dilated gastric in almost one-third of RYGB patients experiencing weight regain.

Management option include the use of sclerotic agents, endoscopic suturing, as well as placement of a ring, band or mesh around the gastric pouch and/or anastomosis.

Another, albeit less frequent complication is the development of a gastro-gastric fistula between the gastric pouch and the excluded stomach. Although rare, such a fistula can can reduce the efficacy of the operation by allowing the passage of food directly into the bypassed intestine. The incidence of fistula has been reported to be preventable through proper surgical technique including the placement of an interposing loop of jejunum between the gastric pouch and remnant stomach.

In some cases, an unrecognised leak or abscess may also promote the formation of a GG fistula.

Thus, in summary, although most instances of weight regain are likely due to dietary, metabolic, or mental health factors, anatomical or “technical” complications (typical for each procedure) must be considered and explored in patients experiencing post-surgical weight regain (or failure to adequately lose weight post-surgery).

As with the initial assessment, diagnostic and management of post-surgical weight regain is best performed by a multi-disciplinary team that has expertise in the bariatric management.

Let me end this discussion by reminding readers that none of these issues speak against undergoing bariatric surgery when indicated. Fortunately, the outcomes in the vast majority of patients are substantially better than the alternative.

Edmonton, AB

Karmali S, Brar B, Shi X, Sharma AM, de Gara C, & Birch DW (2013). Weight Recidivism Post-Bariatric Surgery: A Systematic Review. Obesity surgery PMID: 23996349 


Post-Surgery Weight Regain: Sleeve Gastrectomy

sharma-obesity-verticalsleevegastrectomyContinuing in my discussion of factors that can promote weight regain after bariatric surgery, discussed in our systematic review published in Obesity Surgery, I now turn to the technical or anatomical issues specific to sleeve gastrectomy.

As sleeve gastrectomies have only been performed as a stand-alone procedure for about 5 years, data on weight recidivism is rather limited.

However, there are studies and case reports to suggest that the remnant stomach or sleeve may expand over time and that the size of the gastric sleeve is related to weight loss and possibly weight regain.

How and why the sleeve expands and how exactly such expansion affects satiety and the mode of action of this type of surgery remains unclear and will require further study.

However, weight recidivism after sleeve gastrectomy should prompt appropriate investigations to rule out sleeve dilation (upper gastrointestinal endoscopy, radiographic upper gastrointestinal series) and a large remnant sleeve may require surgical correction or conversion of this procedure to a Roux-en-Y gastric bypass.

Edmonton, AB

Karmali S, Brar B, Shi X, Sharma AM, de Gara C, & Birch DW (2013). Weight Recidivism Post-Bariatric Surgery: A Systematic Review. Obesity surgery PMID: 23996349 


Post-Surgery Weight Regain: Physical Activity

sharma-obesity-exercise1Apart from nutritional, hormonal and mental health factors, our systematic review of the literature, published in Obesity Surgery, also identified the importance of physical activity in supporting post-surgical weight-loss maintenance.

Thus, inadequate physical activity was identified as a contributing factor for weight regain in a survey of 100 obese
patients post-RYGB. Patients who performed physical exercise on a regular basis (three or four times per week, 30 min minimum) showed the lowest weight regain.

One of the potential benefits of bariatric surgery is that it allows patients to become more active by reducing physical disability. On the other hand, biochemical studies have shown that efficiency of skeletal muscle increases as patients lose
weight, requiring a greater intensity of exercise the more weight the individual hopes to keep off. This remains a problem for many patients, as rather than increasing the intensity of exercise, regular physical activity levels tend to drop off over time.

Despite the importance of regular physical activity, it is seldom enough to compensate for excess caloric intake. Thus, even in inactive individuals who fail to lose or tend to regain weight, it is probably of greater importance to monitor and control excessive caloric intake than hope to balance this though excessive physical activity.

Importantly, as many successful post-bariatric patients are still well in the “obese” range, the risk of musculoskeletal injury remains high and it is therefore probably best to focus on non-weight bearing low-impact exercises.

Camrose, AB

Karmali S, Brar B, Shi X, Sharma AM, de Gara C, & Birch DW (2013). Weight Recidivism Post-Bariatric Surgery: A Systematic Review. Obesity surgery PMID: 23996349 


Post-Surgery Weight Regain: Hormonal and Metabolic Factors

sharma-obesity-guthormones2In yesterday’s post, I discussed the importance of dietary factors in weight regain after bariatric surgery.

In this post, I will discuss the role of hormonal and metabolic factors identified in our systematic review of post-surgical weight regain published in Obesity Surgery.

It is now widely assumed that the efficacy of bariatric surgery is not solely dependent on causing a “restriction” or simply “malabsorbtion” of calories.

Rather, there is now growing consensus that the key reason why bariatric surgery works is through its impact on gut hormones and neurological signals from the gut that significantly reduce hunger and/or satiety.

Thus, it is not surprising that in our review we found several studies that noted a significant relationship between post-surgical levels of the “hunger hormone” ghrelin and post-surgical weight regain. Patients who experienced less weight loss or greater weight regain after sleeve gastrectomy and/or roux-en-y bypass surgery demonstrated higher fasting and post-prandial ghrelin levels. Elevated ghrelin levels were also found to correlate with a return of hunger in patients with regain.

Other evidence points to the role of hypoglycaemia in promoting weight regain in some patients. Reactive hypoglycaemia after bariatric surgery may result from the rapid transit of ingested carbohydrates into the small intestine thereby generating an early and significant insulin surge which results in a reactive hypoglycaemia shortly after a meal. This would in turn prompt snacking and increased caloric ingestion resulting in weight regain.

While there is currently no medical treatment to deal with ghrelin elevations, the latter problem can potentially be managed by dietary measures, including the avoidance of high-glycemic index foods.

Given that there are many gut hormones that may be altered by bariatric surgery and their individual roles are still poorly understood, it is clear that we will need further studies to better understand how these factors may explain why some patients failure to lose weight after surgery or show a greater tendency for weight regain.

Chicago, IL

Karmali S, Brar B, Shi X, Sharma AM, de Gara C, & Birch DW (2013). Weight Recidivism Post-Bariatric Surgery: A Systematic Review. Obesity surgery PMID: 23996349