Why the study?
Increases in fat-free mass and fat mass are linked to higher AF risk in observational studies, but whether these associations reflect independent causal processes is unknown.
Do genetically programmed increases in fat-free mass and fat mass independently increase the risk of incident atrial fibrillation?
Do genetically programmed increases in fat-free mass and fat mass independently increase the risk of incident atrial fibrillation?
Genetically programmed increases in both fat-free mass and fat mass independently cause an increased risk of atrial fibrillation.
Both fat-free and fat mass may independently raise AF risk; hypothesis-generating for body-composition interventions pending trials.
AIMS: Increases in fat-free mass and fat mass have been associated with higher risk of atrial fibrillation (AF) in observational studies. It is not known whether these associations reflect independent causal processes. Our aim was to evaluate independent causal roles of fat-free mass and fat mass on AF. METHODS AND RESULTS: We conducted a large observational study to estimate the associations between fat-free mass and fat mass on incident AF in the UK Biobank (N = 487 404, N events = 10 365). Genome-wide association analysis was performed to obtain genetic instruments for Mendelian randomization (MR). We evaluated the causal effects of fat-free mass and fat mass on AF with two-sample method by using genetic associations from AFGen consortium as outcome. Finally, we evaluated independent causal effects of fat-free mass and fat mass with multivariate MR. Both fat-free mass and fat mass had observational associations with incident AF [hazard ratio (HR) = 1.77, 95% confidence interval (CI) 1.72-1.83; HR = 1.40, 95% CI 1.37-1.43 per standard deviation increase in fat-free and fat mass, respectively]. The causal effects using the inverse-variance weighted method were 1.55 (95% CI 1.38-1.75) for fat-free mass and 1.30 (95% CI 1.17-1.45) for fat mass. Weighted median, Egger regression, and penalized methods showed similar estimates. The multivariate MR analysis suggested that the causal effects of fat-free and fat mass were independent of each other (causal risk ratios: 1.37, 95% CI 1.06-1.75; 1.28, 95% CI 1.03-1.58). CONCLUSION: Genetically programmed increases in fat-free mass and fat mass independently cause an increased risk of AF.
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Tikkanen et al. (2019) studied this question.
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