Heart rate is a measure of cardiac cycle frequency that reflects cardiovascular health, metabolic rate, and autonomic nervous system activity. Across mammalian species, larger body sizes are associated with lower heart rates and longer life spans.
A significant induction in human lifespan has been observed over the past two centuries, primarily due to improvements in medical science and social care. However, there remains a concern that the global rise in obesogenic environment may challenge further increase in lifespan.
Previously, the Framingham Heart Study observed higher mortality rates in cardiovascular disease-free individuals with faster heart rates. This study was pivotal in highlighting the potential risks associated with elevated heart rates, yet it did not explore the effects of changes in heart rate over time.
In the current study, scientists have determined the association between resting heart rate and lifespan within human populations. They also explored whether an increase in heart rate over the years correlates with a higher mortality risk. This research marks an important step in exploring a potential causal relationship between heart rate changes and lifespan.
Data from three population-based studies, including the Paris Prospective Study I, the Whitehall I Study, and the Framingham Heart Study, was analyzed to explore the association between resting heart rate and lifespan.
The studies employed linear regression to confirm the inverse relationship between resting heart rate and lifespan and Cox proportional hazards regression to assess mortality risk associated with changes in heart rate over time.
Appropriate statistical analyses were carried out to determine the association between changes in heart rate over the years and mortality risk. The results were adjusted for several classical risk factors, including age, body mass index, smoking, physical activity, diabetes, systolic blood pressure, and cholesterol levels.
Paris Perspective Study I
This study recruited a total of 7,976 healthy French men (aged 42 to 53 years) between 1967 and 1972. A total of 2,387 deaths were reported by December 1993.
The analysis controlling for potential confounding factors revealed a significant inverse association between resting heart rate and lifespan.
Appropriate statistical analyses were carried out to determine the association between changes in heart rate over the years and mortality risk. The results were adjusted for several classical risk factors, including age, body mass index, smoking, physical activity, diabetes, systolic blood pressure, and cholesterol levels.
Whitehall I study
This study recruited a total of 1,226 healthy British men (aged 52 ± 7 years) between 1967 and 1969. A total of 977 deaths were reported by 2008.
The analysis of study data revealed a significant inverse association between resting heart rate and lifespan. However, it is essential to note that changes in heart rate over time were not analyzed in this cohort, limiting the ability to generalize these findings fully.
Framingham Heart Study
This study recruited a total of 4,001 US women (aged 47 ± 16 years) and 3,299 men (aged 45 ± 15 years) between 1971 and 1975. A total of 2,409 deaths were reported among women over a follow-up period of 33 years. Among men, a total of 2,172 deaths were reported over a follow-up period of 31 years.
The findings revealed an inverse association between resting heart rate and lifespan in both men and women. Interestingly, women experienced a 5-year longer lifespan than men for each category of resting heart rate.
Resting heart rate vs. mortality risk
The scientists examined the associations between changes in resting heart rates over 5-year and 8-year periods and mortality risks among 5,589 male participants in the Paris Prospective Study I and 3,299 male and 4,001 female participants in the Framingham Heart Study, respectively.
The analysis controlling for known risk factors and resting heart rate revealed that an increase in resting heart rate over the years can significantly increase mortality rates in both men and women. Specifically, a 10 bpm increase in resting heart rate over 5 years in the Paris Prospective Study I was associated with a 20% higher mortality risk. Similarly, in the Framingham Heart Study, a 10 bpm increase over 8 years led to a 13% higher risk of mortality in men and a 9% higher risk in women.
Study significance
The study has analyzed data from three large-scale populations from the US, UK, and France and found that resting heart rate is inversely associated with lifespan and that an increase in resting heart rate over the years can significantly increase mortality risk in both men and women.
Mammals with larger body sizes generate more heat as a function of their body mass. Similarly, they lose more heat as a result of their body's surface area. Smaller mammals with higher body surface-to-mass ratio, on the other hand, conserve body temperature by increasing their metabolic rate, which in turn determines their heart rate. Thus, heart rate may serve as a surrogate marker for total energy expenditure. This concept of total energy expenditure throughout life may partly explain the inverse association between resting heart rate and lifespan, as larger organisms tend to have lower heart rates and longer lifespans.
In humans, the possibility of reducing heart rate to extend lifespan has been explored primarily in patients with serious illnesses. For instance, beta-adrenergic receptor blockers, which reduce heart rate, have been shown to decrease mortality risk in post-myocardial infarction patients with heart failure. However, no studies have yet investigated whether reducing heart rate can extend lifespan in healthy human populations.
Overall, the study findings highlight that regular heart rate measurement could be a simple and straightforward approach for monitoring human health and lifespan. The results suggest that heart rate might be a target for public health interventions, particularly in environments where unhealthy lifestyle factors contribute to rising heart rates. Further research is needed to explore the potential benefits of heart rate reduction in healthy individuals.
-- By Dr. Sanchari Sinha Dutta, Ph.D.
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