title: Ethnicity and long-term heart rate variability in children.
abstract: BACKGROUND
  Low heart rate variability (HRV) is associated with increased cardiovascular disease risk. South Asians are at increased risk of cardiovascular disease.
  
  
  METHODS
  This cross-sectional, observational study compared long-term HRV between South Asian and White European (EU) children. 155 children (92 White EU, 63 South Asian) aged 8±1 years wore a combined heart rate and activity monitor for 7 days. From 24-h beat-to-beat heart rate recordings, long-term HRV was calculated as the SD of the average RR intervals in each 5 min period (SDANN). Physical activity, daily energy expenditure, percentage body fat and maximal oxygen consumption (VO2max) were calculated using published or commercial algorithms.
  
  
  RESULTS
  SDANN was significantly lower during the 24-h period in South Asian compared with White EU children (113±27 vs 130±28 ms, p<0.01, mean±SD) and during sleep (44±12 vs 54±16 ms, p<0.01, mean±SD). Ethnic differences in HRV were associated with lower levels of physical activity, daily energy expenditure, VO2max, and higher percentage body fat and resting heart rate, in South Asian children. Ethnic differences in HRV persisted despite statistical adjustment for these factors. SDANN was significantly lower in girls, but sex differences were no longer apparent when VO2max, physical activity and energy expenditure were statistically controlled for.
  
  
  CONCLUSIONS
  Our data confirm that South Asian children have lower HRV and reveal the novel information that the reduction is partially independent of physical activity and aerobic fitness.
authors: Division of Metabolic and Vascular Health, Clinical Sciences Research Laboratories, Warwick Medical School, University Hospital, Clifford Bridge Road, Coventry CV2 2DX, UK.
authors: Emma L J
authors: EL
authors: Eyre
authors: James P
authors: JP
authors: Fisher
authors: Elaine C
authors: EC
authors: Smith
authors: Anton J M
authors: AJ
authors: Wagenmakers
authors: Krystyna A
authors: KA
authors: Matyka
mesh_terms: D000704:Analysis of Variance; D000886:Anthropometry / Q000379:methods; D044466:Asian People; D002648:Child; D003430:Cross-Sectional Studies; D015716:Electrocardiography, Ambulatory; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D017678:Sex Distribution; D006113:United Kingdom; D044465:White People