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Intensive lifestyle intervention fails to prevent AF onset in diabetes, overweight/obesity
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An intensive lifestyle intervention was no better than usual care in preventing incidence of atrial fibrillation among patients with diabetes and overweight or obesity, according to new findings from the Look AHEAD study.
Obesity is associated with elevated risk for AF, but the effect of behavioral weight-loss interventions on risk for AF in patients with diabetes was not known, according to the study background. Results from LEGACY and other studies have indicated that losing weight reduces AF symptoms and burden among overweight or obese people with existing AF.
Alvaro Alonso, MD, PhD, and colleagues randomly assigned 5,067 patients aged 45 to 76 years with type 2 diabetes and overweight or obesity but without prevalent AF to an intensive lifestyle intervention or the usual care incorporating diabetes support and education. The intensive lifestyle intervention included weekly individual and group counseling sessions for 6 months (and less frequent sessions thereafter) focusing on caloric reduction and increased physical activity, with a goal of maintaining a weight loss of at least 7%.
In the main analysis of Look AHEAD, the primary outcome, CVD morbidity and mortality, did not differ between the groups. The outcome of interest in the present analysis was onset of AF. Mean follow-up was 9 years.
Alonso, from the division of epidemiology and community health at the School of Public Health, University of Minnesota, Minneapolis, and colleagues identified 294 cases of incident AF during the study period, with similar incidence rates between the groups (intervention, 6.1 per 1,000 person-years; usual care, 6.7 per 1,000 person-years; P = .42).
Assignment to the intervention group did not reduce risk for AF onset (HR = 0.99; 95% CI, 0.77-1.28), they found.
Weight loss during the first year of the intervention was not significantly associated with incidence of AF (HR for top quartile vs. bottom quartile = 0.7; 95% CI, 0.41-1.18), nor was physical fitness improvement in the first year (HR for top quartile vs. bottom quartile = 0.88; 95% CI, 0.55-1.43).
“Given the association between overweight/obese status and an increased risk of AF, we expected to observe a lower risk of AF with weight reduction,” Alonso and colleagues wrote. “However, we failed to see a difference in the risk of AF between the … interventions, despite the fact that the [intensive lifestyle intervention] resulted in modest reduction in body weight.”
Possible explanations, they wrote, include the levels of weight loss not being enough to show a difference in AF risk, use of cardioprotective drugs being less common in the intensive lifestyle intervention group, and very high levels of physical activity being associated with increased risk for AF. – by Erik Swain
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Dan Roden, MD
LEGACY reported a relationship between the extent of weight loss and AF burden in about 300 overweight Australian patients, whereas Look AHEAD failed to find a statistically significant association between weight loss and AF onset in more than 5,000 overweight U.S. diabetics. The different outcomes might reflect differences between countries, the possibility that diabetics are different from non-diabetics, differences in baseline BMIs (32 to 33 kg/m2 in LEGACY; 35 to 36 kg/m2 in Look AHEAD) or differences in AF ascertainment (LEGACY used the Toronto score, while Look AHEAD looked at discharge diagnoses and ECGs). LEGACY was a much smaller study, so it is also conceivable that the very interesting result was a type II error (a false positive).
It is possible that once diabetes is in place, the AF risk is not modifiable by weight loss. However, weight loss still seems to be a desirable target for patients who are obese, but an expectation that AF will be impacted is, at the very least, up in the air.
Further research needs to be done in this area. Among the questions I would like to see answered: Why does diabetes predispose to AF? Why are African Americans at decreased AF risk? And why does hypertension, even if well-controlled, predispose to AF?
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