Bariatric Surgery Reduces MI Risk in Men, But Not Women

June 29, 2011

June 28, 2011 (Gothenburg, Sweden) — New long-term data show that bariatric surgery for weight loss is associated with a significant reduction in the risk of MI in patients with diabetes mellitus. The reduction in risk was observed in men only, however, with the risk of MI statistically nonsignificant in female patients who underwent the weight-loss surgery.

Dr Cristina Maglio

"We know that obesity is associated with diabetes and that diabetes is a significant risk factor for cardiovascular disease," said lead investigator Dr Cristina Maglio (University of Gothenburg, Sweden). "However, we needed to validate whether or not bariatric surgery, which is an effective treatment for weight loss, reduces the incidence of cardiovascular disease events."

Presenting the result of their analysis this week here at the European Atherosclerosis Society 2011 Congress, the researchers studied 607 individuals with diabetes mellitus from the Swedish Obese Subjects (SOS) study. Of these patients, 345 subjects underwent bariatric surgery, the most common surgical procedure being vertical gastroplasty (66%), followed by gastric banding (18%), and gastric bypass (16%). Subjects were, on average, 49 years old and weighed 123 kg. Compared with the 262 control subjects who were randomized to medical therapy, the patients who underwent surgery had a higher body-mass index and higher systolic and diastolic blood pressures.

Overall, the researchers observed a reduction in the cumulative incidence of MI in the surgical arm. MI occurred in 28 subjects randomized to surgery during an average follow-up of 12 years compared with 37 subjects in the control arm (8% vs 14%, respectively; p=0.007).

The benefit of surgery, however, was observed only in men. Among men, who represented 40% of the study cohort, there were 12 MIs in the surgery arm compared with 25 in the control arm, a statistically significant difference (8% vs 24%, respectively; p<0.001). There was no statistically significant difference in event rates in women (8% vs 8%, p=0.726).

After adjusting for various parameters, including the Framingham risk score, investigators report that bariatric surgery was associated with a significant 71% reduction in the risk of MI compared with control therapy in obese diabetic men, but not in women.

Is the Lack of Benefit in Women a Power Issue?

Presenting the data during a moderated session, Maglio noted that the women did not gain any more weight than men during follow-up and that various metabolic variables, including LDL cholesterol, were the same between men and women, confounding variables that might have affected the results. Dr Terje Pedersen (Ullevål University Hospital, Oslo, Norway), the session moderator, suggested the lack of benefit in women might be an issue of statistical power, a hypothesis seconded by the Swedish researchers. Maglio noted that women in the trial were premenopausal, suggesting that not enough events might have yet occurred to detect a difference in clinical outcomes. "Who knows, if we wait 10 more years, maybe we'll see a difference then," she said.

Data recently presented at the American Society for Metabolic & Bariatric Surgery (ASMBS) 2011 Annual Meeting showed similar outcomes with the surgical approach. In that trial, previously reported by heartwire , bariatric surgery significantly reduced the incidence of MI, stroke, and premature death in more than 4000 morbidly obese individuals who underwent the weight-loss surgery. Another study, however, showed that bariatric surgery did not improve survival when assessed out to seven years of follow-up.

Recently, the American Heart Association issued a scientific statement summarizing the most current data on bariatric surgery. The writing committee noted that there is a need for well-designed, randomized controlled trials comparing different surgical techniques with placebo, as well as the different surgeries head-to-head against each other.

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