With the results of a 16 year follow-up study, scientists from the Copenhagen University Hospital have shown that resting heart rate is not just a marker of fitness, as has been generally understood, but is actually an independent risk factor for mortality, even when all other factors have been accounted for.
In other words, we can now say with confidence that between two equally healthy individuals, the one with the slower heartbeat will, statistically speaking, live longer.
The study began in 1985 when doctors began collecting data on healthy middle aged men who had no known heart disease or diabetes. Their resting heart rate, or RHR, was measured and they were divided up into cohorts based on associative data such as diet and levels of exercise. 2,798 men were followed for 16 years and over the course of that period there were 1,082 deaths.
With RHR as a continuous variable, risk of mortality increased with 16% (10–22) per 10 beats per minute (bpm).
What the doctors discovered, after sifting through their mountain of data, is that when all confounding variables are taken into account [such as age and lifestyle risks such as smoking or drinking habits], the resting heart rate, even in perfectly healthy individuals, is directly related to likelihood of premature death.
In other words, the faster your heart beats, the less time you have on Earth. Interestingly, this also holds true in the animal kingdom, as species with faster heartbeats tend to lead shorter lives. However it has always been assumed in human beings that a slower heart rate was purely the result of healthy living and exercise.
Compared to men with heart rates of 50 beats per minute, those over 70 had a 51% greater chance of death. At over 80 beats per minute the rate of death was doubled.