NEW ORLEANS – Results of a new 40,000-patient Swedish observational study provide the strongest evidence to date suggesting a causal relationship between bariatric surgery and reduced risk of heart failure, according to Johan Sundström, MD.
The study, which included patients drawn from two large Swedish national registries, demonstrated that bariatric surgery was associated with a 46% reduction in the incidence of heart failure during a median 4.1 years of follow-up, compared with an intensive lifestyle modification program for weight loss.
“These are observational data, but it’s a very large study population – and probably there will never be a large randomized trial of bariatric surgery versus weight loss through intensive lifestyle modification as a means of reducing the risk of heart failure,” Dr. Sundström, professor of epidemiology and a cardiologist at Uppsala (Sweden) University, said at the American Heart Association scientific sessions.
The study included 25,804 bariatric surgery patients in SOReg, the Scandinavian Obesity Surgery Registry, and a matched comparator group of 13,701 participants in a Swedish national registry of obese participants in a commercial Sweden-based intensive structural lifestyle modification program for weight loss called Itrim. The two groups were matched for baseline body mass index, which was a mean of 41.5 kg, and numerous other demographic factors and comorbid conditions. Participants weighed an average of 119 kg at baseline. None of the subjects had a history of heart failure.
The bariatric surgery group lost substantially more weight than did the lifestyle modification group: an average loss of about 35 kg after 1 year, which was 18.8 kg more than in the lifestyle modification group. After 2 years, the bariatric surgery group had an average of 22.6 kg more weight loss than did the comparison group.
The primary outcome was hospitalization for new-onset heart failure during a median 4.1 years of follow-up. Subjects were well below the age range when the incidence of heart failure accelerates – they averaged 41 years of age – but 73 of them did develop heart failure during follow-up. The incidence was 46% lower in the bariatric surgery patients. This supports the study hypothesis that bariatric surgery leads to a low incidence of new-onset heart failure, compared with intensive lifestyle modification because of its larger weight loss effect.
When Dr. Sundström and his coinvestigators combined the two study groups, they found that a 10-kg weight loss at 1 year was associated with a 23% reduction in the risk of heart failure during follow-up, irrespective of whether the weight loss was achieved surgically or through the lifestyle program.
“A great way of studying causality is to take away the exposure and note what happens to the outcome. If there’s a causal link, then if you take away the risk factor – in this case, obesity – the disease should go away,” he explained in a video interview.
The reduced risk of heart failure in the bariatric surgery patients wasn’t because of fewer acute MIs. Indeed, their acute MI rate during follow-up was similar to that of the lifestyle modification group. But bariatric surgery was associated with relative risk reductions of 35%-37% for atrial fibrillation or need for diabetes or blood pressure–lowering medications at 1 year – and atrial fibrillation, diabetes, and hypertension are all established risk factors for heart failure, Dr. Sundström noted.
The Itrim intensive lifestyle modification program entailed an initial very-low-energy diet for the first 3 months in order to achieve massive weight loss, followed by a 9-month maintenance program involving motivational counseling, exercise, behavioral therapy, and a restricted diet.
Dr. Sundström said he and his coinvestigators plan to continue the study and expand it to look at differences in additional cardiovascular endpoints as patients age.
The study was funded by the U.S. National Institute of Diabetes and Digestive and Kidney Diseases, Uppsala University, the Karolinska Institute, and the Swedish Research Council. Dr. Sundström reported serving as a scientific advisor to Itrim.