Lean body mass only anthropometric risk factor for atrial fibrillation
Lean Body Mass Is the Predominant Anthropometric Risk Factor for Atrial FibrillationFenger-Grøn M, Overvad K, Tjønneland A and Frost L. - JACC 2017; 69(20):2488-2497
As the incidence of atrial fibrillation (AF) increases and it is associated with many adverse effects and human and health-economic costs, identification of modifiable risk factors is high desired [1-5]. Although obesity is frequently emphasized as being one of the modifiable risk factors, this association may be largely due to correlations between weight, BMI, waist and hip circumference, waist-to-hip ratio, fat mass, fat percentage, height and lean body mass [6,7].
In the present study, data from the Danish Diet, Cancer and Health cohort was updated (n=55 273) to depict correlations between the 9 above mentioned anthropometric measures and to assess their associations with risk of AF or atrial flutter under mutual adjustment. Median follow-up was 16.9 years.
- 1473 women and 2395 men developed AF, with a median time to event of 11.5 years.
- Almost all 9 anthropometric measures were positively correlated with each other, generally with Pearson’s R >0.6 in both sexes.
- Also, all 9 measures highly significantly positively associated with risk of AF (HR lean body mass 1.37, 95% CI 1.33-1.42, fat mass HR 1.25, 95% CI 1.22-1.29, fat % HR 1.16, 95% CI 1.12-1.20, HR height 1.29, 95% CI 1.24-1.33, HR weight 1.33, 95% CI 1.29-1.36, HR BMI 1.22, 95% CI 1.18-1.26, HR hip circumference 1.26, 95% CI 1.22-1.30, HR waist circumference 1.24, 95% CI 1.20-1.28, HR waist-to-hip ratio 1.08, 95% CI 1.05-1.12, all P<0.0001).
- All HRs adjusted for each other ranged from 1.08 (95% CI 1.05-1.12) to 1.37 (95% CI 1.33 to 1.42), however when also adjusted for lean body mass, almost none of the associations were significant anymore: HR fat mass 1.02 (95% CI 0.98-1.06, P=0.35, fat % 1.01 (95% CI 0.98-1.05, P-0.52), height 1.05 (95% CI 1.01-1.10, P=0.03), weight 1.03 (95% CI 0.97-1.09, P=0.38), BMI 1.00 (95% CI 0.96-1.04, P=0.97), hip circumference 1.02 (95% CI 0.98-1.04, P=0.98), waist-to-hip ratio 0.99 (95% CI 0.95-1.02, P=0.47).
- On the other hand, the association for lean body mass remained almost unchanged when adjusted for any of the 9 other measures: HR 1.36 (95% CI 1.30-1.41) corrected for fat mass, 1.37 (95% CI 1.32-1.41) corrected for fat%, 1.33 (95% CI 1.28-1.39) corrected for height, 1.34 (95% CI 1.26-1.43) corrected for weight, 1.38 (95% CI 1.32-1.43) corrected for BMI, 1.35 (95% CI 1.30-1.41) corrected for hip circumference, 1.37 (95% CI 1.32-1.43) corrected for waist circumference and 1.38 (95% CI 1.34-1.42) corrected for waist-to-hip ratio, all P<0.0001.
- The observed incidence rates for AF for both sexes developed slightly differently with age, but the estimated association for lean body mass corrected this difference in risk levels below the age of 70.
All 9 anthropometric measures height, weight, BMI, hip and waist circumference, waist-to-hip ratio and bioimpedance-derived fat mass, lean body mass and fat percentage were, as expected, positively associated with AF risk, however correlations between measures were also present. After multiple correction, lean body mass was the predominant anthropometric driver for AF risk, whereas none of the traditional obesity-related measures proved to have any independent influence. This questions the role played by fat in the AF etiology.