Aging and nonlinear heart rate control in a healthy population

Area of Science:

• Cardiovascular Physiology
• Nonlinear Dynamics
• Autonomic Nervous System

Background:

• Cardiovascular control is increasingly studied using nonlinear dynamics.
• Large-scale studies are needed to establish healthy physiological ranges for nonlinear heart rate variability (HRV) indexes, considering gender and age variations.
• Understanding age and gender effects on nonlinear HRV is crucial for interpreting cardiovascular health.

Purpose of the Study:

• To investigate the influence of gender and age on nonlinear heart rate variability (HRV) indexes.
• To analyze day-night variations in nonlinear HRV.
• To explore the relationship between nonlinear HRV and advancing age.

Main Methods:

• Employed nonlinear dynamics methods including 1/f slope, fractal dimension, correlation dimension (CD), Lyapunov exponent (LE), and approximate entropy (ApEn).
• Analyzed 24-hour Holter ECG recordings from 135 women and 141 men (aged 18-71 years), divided into daytime and nighttime periods.
• Utilized surrogate data analysis to assess the significance of CD values.

Main Results:

• All nonlinear HRV indexes, except CD in females, showed significant day-night variations.
• All nonlinear indexes demonstrated a significant correlation with age, declining as age increased.
• Fractal dimension and ApEn showed a stabilization in their age-related decline after age 40.
• No significant gender differences were found in the nonlinear HRV indexes.
• Increased nonlinear complexity was observed during nighttime recordings.

Conclusions:

• Nonlinear HRV indexes decrease with advancing age, suggesting a reduction in autonomic modulation.
• Vagal pathways appear to play a significant role in generating nonlinear heart rate fluctuations.
• Nighttime recordings exhibit higher nonlinear behavior compared to daytime.
• The findings highlight the importance of age in nonlinear HRV analysis, with gender playing a less prominent role.