Lean body mass—not obesity—predominant risk factor for AFib

When it comes to heart problems, one go-to piece of advice for overweight patients was to lose weight. But cardiologists may have to look more deeply into the correlation between obesity and atrial fibrillation.

The research, published in May issue of the Journal of the American College of Cardiology, examined 3,868 atrial fibrillation (AFib) outcomes collected from the Danish Diet, Cancer and Health Study. Led by Morten Fenger-Grøn, MSc, with Aarhus University in Denmark, the study found no association between risk factors and obesity-related measurements.

“Lean body mass was the predominant anthropometric driver of AFib risk, whereas none of the traditional obesity-related measures proved to have any independent influence,” Fenger-Grøn and colleagues wrote. “The pattern was consistent between the sexes and over time. Flexible modeling of fat and lean body mass did not reveal any decisive underlying nonlinearity.”

Of 55,273 participants in the Diet, Cancer and Health Study, 3,868 developed AFib (1,473 women and 2,395 men) with a median time to event of 11.5 years. The association for lean body mass remained virtually unchanged when adjusted for any of eight other anthropometric measures, despite strong mutual correlations.

The study also shed light on the differing rates of AFib for men and women.

“Below 70 years of age, the estimated association for lean body mass accounted well for the observed and well-known, but not fully explained, AF incidence differences between men and women,” wrote Fenger-Grøn et al. “Above 70 years of age, the sex difference predicted from lean body mass exceeded the observed difference, possibly because predisposing comorbidities have a more decisive influence.”

The authors noted the sample may constitute a relatively healthy, economically privileged group that tended to be from more urban areas. Though fully supporting the study’s conclusions, the team also recommended results be interpreted with caution as inspiration for further research, rather than evidence that should guide current practices.