Circadian reference values for different endpoints of heart rate variability

While it is known that endpoints of HRV undergo a circadian variation, time-specified reference value ranges are lacking. To fill this void, peer-group reference standards are presented. They are derived on the basis of data from 219 healthy males in 8 age groups: 5-10 years, 10-20 years, 20-30 years, 30-40 years, 40-50 years, 50-60 years, 60-70 years and >70 years, and from 117 healthy females in 4 age groups: <20 years, 20-40 years, 40-60 years, and >60 years. The spectral Q component (Q for quadrisecundan, rather than `HF') and the D/Q ratio (D for decisecundan, rather than `LF/HF') were computed hourly for 24 hours. Time-specified reference limits (chronodesms) were computed for each variable in each group as 90% prediction limits. Circadian chronodesms in different age groups indicate that both Q and D/Q vary greatly as a function of age. Chronodesms here proposed may serve for evaluating risk and the efficacy of various interventions.