About physiological age

The science behind healthy aging

Heart rate variability (HRV) measures the variation in time between each heartbeat, which is controlled by the autonomic nervous system. A higher HRV generally indicates a healthy balance between the sympathetic and parasympathetic branches of the autonomic nervous system, reflecting good cardiovascular health, resilience, and recovery capabilities.

HRV naturally declines with chronological age due to the aging process, which affects the autonomic nervous system and the cardiovascular system ^[1]. HRV normal ranges show a marked decline in HRV after age 40. However, lifestyle choices and overall health can slow or even reverse this decline ^[2]. Higher HRV values typically suggest a younger physiological age, indicating better cardiovascular health and a lower risk of chronic conditions. Conversely, lower HRV values can indicate an older physiological age, reflecting higher stress levels, poorer health, and a higher risk for cardiovascular and other chronic diseases ^{[3], [4]}.

How is physiological age estimated?

Physiological age is estimated from resting HRV by comparing an individual’s RMSSD—a measure of beat-to-beat variability—to population norms for different age groups. RMSSD typically decreases with age and in the presence of chronic diseases affecting the autonomic nervous system and cardiovascular function. Since HRV is inversely related to resting heart rate, a normalized HRV score is calculated by dividing RMSSD by the square root of the average heartbeat interval (Mean RR). This normalized HRV metric is then used to estimate an individual’s physiological age.

The physiological age estimate derived as described above shows very high correlation with chronological age values presented as group medians for different age groups. In the figure, median values of the normalized HRV metric are presented for different age groups, while the curve illustrates the predicted physiological age. Data is taken from the Autonomic Aging dataset ^{[5], [6]}, which limits the maximal range provided by the physiological age estimate to 18-86 years.

The physiological age estimate is included in the readiness analytics offered by Kubios, making it accessible to anyone using the Kubios HRV App for personal wellness monitoring, as well as all third-party apps that integrate Kubios Readiness Analytics. Similar to the Readiness index, consistent daily measurements enhance the initial accuracy of the physiological age estimate, utilizing up to 90 days of historical data.

Factors affecting physiological age

Key factors that can impact heart rate variability and, consequently, the physiological age estimate include:

• Stress: Chronic stress can lower HRV by over-activating the sympathetic nervous system.
• Sleep: Poor sleep quality or insufficient sleep can negatively impact HRV.
• Physical Inactivity: Passive lifestyle and lack of regular aerobic exercise reduces HRV over time, reflecting diminished cardiovascular fitness.
• Unhealthy Diet: Unbalanced diet, low in nutrients and high in processed foods can negatively impact autonomic function, lowering HRV.
• Lifestyle Habits: Habits like smoking, excessive alcohol consumption, and sedentary behavior can lower HRV.

How to improve your physiological age?

Here are some actionable tips for enhancing heart rate variability and improving your physiological age:

• Stress Management: Incorporate relaxation techniques such as meditation, deep breathing, or yoga.
• Healthy Sleep Habits: Prioritize 7-9 hours of quality sleep per night and maintain a regular sleep schedule.
• Regular Exercise: Engage in consistent, moderate-intensity aerobic exercise like walking, cycling, or swimming.
• Balanced Diet: Focus on a diet rich in fruits, vegetables, whole grains, and lean proteins.
• Healthy Lifestyle Choices: Avoid smoking, limit alcohol consumption, and stay active throughout the day.