Rest heart rate and life expectancy

Area of Science:

• Comparative physiology
• Biophysics
• Evolutionary biology

Background:

• Mammalian species exhibit an inverse semilogarithmic relationship between heart rate and life expectancy.
• The product of heart rate and life expectancy suggests a species-specific, predetermined number of heartbeats per lifetime.

Purpose of the Study:

• To investigate the concept of a fixed number of heartbeats per lifetime across mammalian species.
• To explore the relationship between heartbeats per lifetime, body weight, and metabolic rate.
• To determine if life span is predetermined by cellular energetics.

Main Methods:

• Calculated the number of heartbeats per lifetime for various mammalian species.
• Plotted heartbeats per lifetime against life expectancy and body weight using an allometric scale.
• Analyzed universal biologic scaling and mortality data related to basal energy consumption per body atom per heart beat.

Main Results:

• The number of heartbeats per lifetime among mammals is remarkably constant within an order of magnitude, averaging 7.3 ± 5.6 x 10^8 beats.
• Basal energy consumption per body atom per heart beat is consistent across species (approximately 10^-8 O2 molecules/heart beat).
• This yields a mean of 10 x 10^8 heartbeats per lifetime, suggesting life span is linked to cellular energetics.

Conclusions:

• Life span appears predetermined by the fundamental energetics of living cells.
• The inverse relationship between heart rate and life span is likely an epiphenomenon, with heart rate serving as a marker of metabolic rate.
• The potential for extending human life through cardiac slowing remains uncertain and requires further investigation.