Preoperative weight loss, even at a moderate degree (ie >0% to <5%), is associated with lower risk of 30-day mortality following bariatric surgery, according to a study involving nearly half a million patients by researchers from University of Iowa College of Public Health, the University of Iowa, Iowa City, and Renmin Hospital of Wuhan University, Wuhan, China.
The authors study noted that weight loss requirements prior to bariatric surgery varies among patients, physicians and health insurance payers, and current clinical guidelines do not require preoperative weight loss because of a lack of scientific support regarding its benefits. In the paper, ‘Association of Preoperative Body Weight and Weight Loss With Risk of Death After Bariatric Surgery’, published in JAMA Network Open, the researchers sought to examine the association of preoperative body mass index (BMI) and weight loss with 30-day mortality after bariatric surgery.
The study included 480,075 patients (the majority of patients were women (383,265; n=79.8%) who underwent bariatric surgery from 2015 to 2017 in the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program, which covers more than 90% of all bariatric surgery programs in the US and Canada (patients were excluded if their preoperative BMI was <35.0 or if they reported weight gain before surgery).
Mean percentage of reduction in body weight before surgery was 4.0% and compared with patients without weight loss before surgery, patients with greater weight loss (ie, ≥10%) prior to bariatric surgery were slightly older (p<0.001) and more likely to be male (p<0.001) and non-Hispanic white (p<0.001).
Patients with greater weight loss were more likely to undergo Roux-en-Y gastric bypass (p<0.001), vs with patients without weight loss before surgery and those with greater weight loss had higher highest recorded preoperative BMI (p<0.001), lower preoperative BMI closest to the day of surgery (p<0.001) and were less likely to have smoked tobacco during the past year (p<0.001) and more likely to have two or more comorbid conditions at baseline (p<0.001).
In total, there were 511 (0.1%) deaths within 30 days following bariatric surgery. Compared with patients with no preoperative weight loss, patients with weight loss greater than 0% to less than 5.0%, 5.0% to 9.9%, and 10.0% and greater had 24%, 31%, and 42%, respectively, lower risk of 30-day mortality.
“Although current clinical guidelines do not require preoperative weight loss and a decision to perform bariatric surgery should not be based on whether and how much preoperative weight loss is achieved, it may be beneficial for patients with obesity to be referred to an established weight loss program before surgery to reduce the risk of mortality,” the authors noted. “…Further investigation is needed to replicate our findings in a setting with further information on how weight loss was achieved and to inform future updates of clinical guidelines regarding bariatric surgery.”
In an invited commentary, ‘Preoperative Weight Loss Before Bariatric Surgery—The Debate Continues’, Drs Micaela M Esquivel and Dan Azagury from Stanford University School of Medicine, Stanford, CA, noted that venous thromboembolism is a primary cause of mortality after bariatric surgery and that the current study could not report on cause of death nor control for perioperative anticoagulation prophylaxis practices that may have affected postoperative mortality.
Furthermore, they add that the most recent position statement from the American Society for Metabolic and Bariatric Surgery concluded that there is a lack of evidence showing that insurance-mandated preoperative weight loss has any clear association with morbidity or mortality.
“Perhaps the answer is not really about maximising preoperative weight loss; perhaps the answer is treating patients in the earliest possible stage of their disease to negate the increased morbidity and mortality that is associated with more advanced disease and higher BMI,” they concluded. “Patients should be provided early and rapid access to the care they need; in this case, that means access to a life-saving procedure without artificial insurance barriers, such as duration-based mandatory weight loss.”
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