AGE-RELATED BRADYCARDIC CHANGES AND PRESERVED DAILY AUTONOMIC MODULATION IN CONDITIONALLY HEALTHY MEN BASED ON 24-HOUR HOLTER DATA
DOI:
https://doi.org/10.31861/biosystems2025.03.350Keywords:
heart rate variability, autonomic nervous system, bradycardia, daily modulation, men, age-related changesAbstract
This article presents an assessment of age-related changes in heart rate (HR) and the circadian modulation of heart rate variability (HRV) indices in apparently healthy men across different age categories. A total of 86 individuals aged 18-82 years were examined and stratified according to the WHO classification into four groups: Group 1 (18-43 years, n=17, mean age 30.6 ± 8.5 years), Group 2 (46-59 years, n=19, mean age 55.8 ± 4.2 years), Group 3 (60-72 years, n=35, mean age 65.1 ± 3.7 years), and Group 4 (76-82 years, n=16, mean age 78.1 ± 1.9 years). Ambulatory 24-hour Holter ECG monitoring was performed at MED-SOYUZ LLC (Sumy, Ukraine) using the “CardioSens CS” system (HAI-MEDICA LLC, Kharkiv, Ukraine). Time-domain HRV metrics were analysed – 24-hour mean HR and daytime mRR, SDNNi, RMSSD – together with spectral indices LF, HF, LF/HF and AMo%. Median 24-hour HR across age groups 1–4 was 67.56 (61.75; 73.38), 68.89 (64.22; 73.56), 62.20 (57.53; 66.87) and 58.69 (52.88; 64.50) bpm, respectively, indicating a shift from higher values in younger and middle-aged men (groups 1–2) towards lower rates in older men (groups 3–4). Daytime mRR increased mainly after 60 years of age: 882.19 (800.79; 963.59), 852.58 (770.18; 935.98), 958.31 (876.91; 1039.71) and 1007.19 (909.39; 1104.99) ms in groups 1–4, respectively. SDNNi did not differ significantly between age groups (87.12 (58.82; 115.42), 99.07 (69.77; 128.37), 79.89 (50.59; 109.19) and 97.94 (69.64; 126.24) ms), whereas RMSSD showed a tendency to decrease in group 3 with partial recovery in group 4 (58.56 (32.26; 84.86), 50.83 (24.53; 77.13), 27.49 (1.19; 53.79) and 37.81 (11.51; 64.11) ms). Recordings were segmented into daytime (08:00–22:00) and nighttime (22:00–08:00). Normality was tested with the Shapiro-Wilk test (non-normal distributions for most variables, p < 0.05); between-group comparisons used the Mann-Whitney U test (p < 0.05 for HR and mRR). A pronounced age-related bradycardic trend was found: HR decreased with age (ρ=-0.41; p = 0.0047), while mRR increased (ρ=+0.43; p = 0.0006). Global HRV indices (SDNNi, RMSSD, TP, LF, HF) did not differ significantly between groups (p > 0.16), whereas daily modulation was preserved: LF/HF day > night (p = 0.00055), LF day > night (p = 0.0056), HF night > day (p = 0.073). AMo% showed a weak upward tendency (ρ=+0.13; p > 0.05), and body mass index correlated with a decrease in LF/HF (p = 0.085). Overall, these findings indicate age-related bradycardia without a marked decline in global HRV and with preserved circadian autonomic regulation, suggesting adaptive robustness of the ANS in healthy men and supporting further research into cardiovascular risk.
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