The incidence of heart attack, stroke or death (major adverse cardiovascular event, MACE) can be reduced by 50% according to a new study entitled, “Does bariatric surgery reduce the risk of major cardiovascular events? A retrospective cohort study of morbidly obese surgical patients.”
“Bariatric surgery has long been considered an effective treatment for morbid obesity and type 2 diabetes, but mounting data suggests bariatric surgery can also prevent a multitude of diseases, particularly heart disease and stroke,” said Dr John David Scott, study co-author and a bariatric surgeon at GHS University Medical Center. “Clearly significant weight loss plays a role, but further research is needed to understand the relationship between the amount lost and the amount of risk reduction, and whether or not the incidence of these diseases returns to the same level if someone regains the weight.”
Several previous studies have documented that gastric bypass surgery and adjustable gastric banding reduce the prevalence of cardiovascular risk factors. However, limited data have linked bariatric surgery directly to reductions in major adverse events, such as MI and stroke.
Researchers from Greenville Hospital System University Medical Center reviewed data from the inpatient database maintained by the South Carolina Office of Research and Statistics and mortality data from the South Carolina Department of Health and Environmental Control. They identified 43,104 morbidly obese patients, 10,564 of whom had one of the surgical procedures of interest. Exclusions for incomplete data, history of MACE, or early events left 9,140 patients for analysis: 4,747 who had bariatric surgeroutcomes, endpoints, y, 3,066 who had orthopedic procedures, and 1,327 who had GI surgery. The primary endpoint was the time to first occurrence of MI, stroke, or death from any cause. Secondary outcomes were the individual outcomes included in the composite primary endpoint.
There were some different baseline characteristics that favoured the bariatric group with patients in this group presenting a younger and with higher number of females. In addition, the prevalence of coronary artery disease was lower in this group (5.3% of bariatric patients versus 10.9% of the orthopaedic patients and 11.4% of the GI patients (p<0.001)).
The mean follow-up period was longer in in the orthopaedic and GI control groups (25 to 26 months) versus the bariatric group (13.7 months).
The difference in follow-up duration is explained by patients in the control groups requiring subsequent hospitalisation.
The composite endpoint occurred in 3.6% of the bariatric patients compared with 11.9% in the orthopaedic group and 16.2% of the GI patients. Unadjusted event-free survival was significantly higher in the bariatric group compared with the control groups at all points in time (p<0.001). For example, five-year event-free survival was 84% in the bariatric group, 72% in the orthopaedic group, and 65% in the GI group. Multivariate analysis of the composite endpoint showed that the bariatric group had a hazard ratio of 0.72 compared with the orthopaedic group and 0.48 compared with the GI group. Analysis of differences in the components of the primary endpoint showed risk reductions of 25% to 50% in favour of the bariatric group.
Five years after bariatric surgery, the estimated incidence of heart attack was about 50% less, and stroke 30 to 50% less when compared to the control groups. The estimated relative risk of death was also 20 to 55% lower in the bariatric surgery group compared to the other groups.
“We believe our study builds on this previous foundation and takes it a step further to look at actual event rates,” said Scott. “It is unique in that it tracked actual cardiovascular events in a large number of patients coming from a variety of settings and a variety of providers. This gives the study greater power and permits greater generalization of the results to a broader population.”
“The impact of bariatric surgery on both cardiovascular risk factors and events is an important area of emerging study,” said Anita Courcoulas, director of Minimally Invasive Bariatric & General Surgery at University of Pittsburgh Medical Center, and not affiliated with this study. “The authors’ findings are suggestive of an association between undergoing bariatric surgery and improved event-free survival. This relationship needs to be further explored with prospective clinical data, but still highlights the importance of understanding the broader impact of bariatric surgery on long-term outcomes.”