Does your resting heart rate say anything about how fast you are ageing?
A structurally high resting heart rate, certainly above 80 to 90 beats per minute, is associated with a clearly higher risk of premature death. Exercising to lower your resting heart rate is worthwhile, but a very low heart rate at an older age is not always a good sign: if in doubt, discuss it with your doctor.
A higher resting heart rate is clearly associated with a shorter lifespan. At a heart rate above 90 beats per minute, the risk of death is roughly 56% higher than at a heart rate of 61 to 70 beats per minute. The risk of dying from cardiovascular disease at that high heart rate is even more than twice as great. This association has been found robustly across multiple observational studies, including in people aged 70 to 90. Every additional 10 beats per minute corresponds to a 13 to 35% higher risk of death, depending on your age.
Whether this is causal -- meaning whether a high heart rate genuinely accelerates ageing -- is less certain. Genetic research (so-called Mendelian randomisation studies) suggests that a causal relationship exists. Animal research also shows that artificially slowing the heart rate extends lifespan, but that is not yet proof in humans. The hypothesis that a high heart rate speeds up the biological clock through greater oxidative stress and inflammation does exist, but has not been convincingly demonstrated in humans so far.
At the same time, there are two important nuances. First: the older you get, the more the significance of your resting heart rate changes. In people over the age of 95, the level of the resting heart rate was no longer a predictor of survival. And a falling heart rate at an advanced age sounds favourable, but can also indicate an ageing sinus node -- the heart's natural pacemaker -- that is functioning less well. That is actually a risk factor. Second: only about 23% of the variation in resting heart rate is genetically determined. The rest is related to lifestyle, fitness and state of health. This means that exercise can genuinely make a difference.
A low resting heart rate is therefore not proof in itself that you are biologically younger. It is more of a signal: a structurally high resting heart rate, certainly above 80 or 90 beats per minute, is reason to take your fitness and cardiovascular health seriously. A resting heart rate that drops sharply to 50 beats per minute or lower at an older age, without you being a trained athlete, is also something worth discussing with your doctor.
Claims based on observational studies, a large twin study (n=4282), the Jerusalem Longitudinal Cohort Study, and Mendelian randomisation analyses. The causal interpretation is supported by genetic research but has not yet been confirmed in randomised interventions in humans. Biological-mechanistic claims about ageing are based on animal research and hypotheses.