1 Department of Pediatrics, Université de Montréal, Montreal, QC, Canada.
2 Centre de Recherche, Centre Hospitalier Universitaire Sainte-Justine, 3175 Chemin Côte Sainte-Catherine, Montreal, QC, H3T 1C5, Canada.
3 Department of Pediatrics, CHU de Rennes, Rennes, France.
4 Department of Mathematics and Statistics, Concordia University, Montréal, QC, Canada.
5 PERFORM Centre, Concordia University, Montreal, QC, Canada.
6 School of Kinesiology and Physical Activity Sciences, Université de Montréal, Montreal, Canada.
7 Faculté de Pharmacie, Université Laval, Quebec, QC, Canada.
8 Institut Universitaire de Cardiologie et de Pneumologie, Quebec, QC, Canada.
9 Family Medicine Department, McGill University, Montreal, QC, Canada.
10 Department of biochemistry & chemistry, Faculty of Sciences, University of Moncton, Moncton, Canada.
11 Department of Pediatrics, Université de Montréal, Montreal, QC, Canada. melanie.henderson.hsj@gmail.com.
12 Centre de Recherche, Centre Hospitalier Universitaire Sainte-Justine, 3175 Chemin Côte Sainte-Catherine, Montreal, QC, H3T 1C5, Canada. melanie.henderson.hsj@gmail.com.
13 School of Public Health, Department of Social and Preventive Medicine, Université de Montréal, Montreal, Canada. melanie.henderson.hsj@gmail.com.

Purpose: Data on associations between adiposity and heart rate variability (HRV) in prepubertal children are limited. We examined the associations between adiposity indices and HRV, independent of lifestyle behaviors, comparing multiple indicators of adiposity, and explored differences between boys and girls.

Methods: Data stem from 469 participants of the QUALITY cohort (630 children aged 8-10 years with a parental history of obesity). Adiposity indices included waist-to-height ratio, body mass index (BMI) percentiles and categories (overweight, obesity), dual-energy x-ray absorptiometry (DEXA) defined fat mass percentage and android/gynoid ratio. HRV indices in the frequency and the spectral domain were derived from a daytime 3-h Holter recording. Multivariable linear regression models were adjusted for age, sex, Tanner stage, physical activity, screen time, and fitness. Interactions between sex and adiposity were tested.

Results: Greater adiposity was associated with decreased parasympathetic modulation and increased sympathetic dominance. Waist-to-height ratio was associated with lower parasympathetic activity: root mean square of the successive differences (RMSSD) [B = -23.32, 95% confidence interval (CI) -42.42, -4.22], pNN50 (B = -16.93, 95% CI - 28.58, - 5.27), LF/HF ratio (B = 1.83, 95% CI 0.97-2.70). Patterns of association were similar for android/gynoid ratio. Overweight was not associated with altered HRV. Obesity was negatively associated with RMSSD and pNN50 and positively with LF/HF ratio. Greater fat mass percentage was associated with lower RMSSD, pNN50, and HF, and increased LF/HF ratio. There were no differences between boys and girls.

Conclusions: Specific markers of adiposity relate to altered HRV in childhood, with waist-to-height ratio being potentially a more relevant marker of HRV than BMI and more pragmatic than percent body fat.

Trial registration: NCT03356262, 11 November 2017.