Table 3.

A summary of clinical studies with respect to age-related changes in heart rate variability

Year	Authors	Subjects	Main findings
1998	Umetani K, et al. [55]	260 healthy subjects (112 male, 10–99 years old)	SDNN and SDANN decreased with aging in a quadratic regression pattern. The most marked decrease occurred between the second and third decades, after which time-domain declined only gradually. Beyond age 80, HRV again began to decline more rapidly
2016	Almeida-Santos MA, et al. [57]	1743 community-based participants (40–100 years)	SDNN, SDANN, and SDNN index decreased linearly with age. U-shaped pattern for rMSSD and pNN50, with the nadir between 60 and 69 years for both genders
2019	Tan JPH, et al. [58]	45 healthy participants (49–82 years)	There was no association between age and resting-state HRV (RMSSD, TP, HF spectral power), yet HRV in the 2 h preceding sleep was associated with age. Older participants showed greater HRV
2020	Geovanini GR, et al. [59]	543 healthy participants (41% male, 40 ± 14 years)	RMSSD and pNN50 showed U-shaped distribution and reversal increase above 60 years old. SDNN and SDANN decreased linearly by age
2020	Choi J, et al. [54]	291 healthy participants (144 men) aged 19–69 years	HRV indices (HF, LF, VLF, TP, SDNN, HRV index, and pNN50) show a decreasing trend with age in healthy Korean adults
2020	Hernández-Vicente A, et al. [60]	Young adults (n = 20; 21 ± 2 years), octogenarians (n = 18; 84 ± 3 years), centenarians (n = 17; 102 ± 2 years)	HF, LF, SDNN, and pNN50 all present an age-related reduction. SDNN showed a correlation with survival prognosis in centenarians

HF high frequency, HRV heart rate variability, LF low frequency, pNN50 percentage of successive RR intervals that differ by more than 50 ms, RMSSD root mean square of successive RR interval differences, SDANN standard deviation of the average NN intervals for each 5-min segment of a 24-h HRV recording, SDNN standard deviation of NN intervals, TF total power, VLF very low frequency