Amsterdam, April 16th 2013-
Also this week MedZine brings you the latest medical news on various medical specialisms. In this editorial, we want to highlight an interesting discovery about the predictive value of a person’s heart rate. According to Danish researchers, a high heart rate may be an independent risk factor for mortality. In the British Medical Journal, they report that men with higher heart rates were more likely to die, even if these men were physically fit.
The researchers tracked the health of just under 3000 men who were part of the Copenhagen Male Study. In 1971 a doctor asked all participants about their health and lifestyle, including smoking and exercise, and examined them. A cycling test was used to test their cardiorespiratory fitness at three different levels of exertion. In 1985-6, just under 3000 of the original participants underwent a further check-up, which included measurements of height, weight, blood pressure and the resting heart rate. When the researchers checked national Danish registers in 2001, they found that just over a third (1082) of the men had died.
According to the researchers, a high resting heart rate was associated with lower levels of physical fitness, higher blood pressure and greater weight. Men who were physically active tended to have lower resting heart rates. But the results also showed that the higher the resting heart rate, the higher was the risk of death, irrespective of fitness.
After adjusting for age, smoking, alcohol, physical activity, fitness, and other clinical measures, the researchers found that a resting heart rate in 1985-6 of between 51 and 60 beats per minute was associated with a 40% increased risk of death, when compared with a rate under 50, while a rate between 81 and 90 beats per minute doubled the risk and one above 90 beats per minute tripled the risk.
The researchers concluded: “We found that irrespective of level of physical fitness, subjects with high resting heart rates do fare worse than subjects with lower heart rates. This suggests that a high resting heart rate is not a mere marker of poor physical fitness, but is an independent risk factor.”
There are however, some remarks to make on this conclusion. According to Tim Chico, senior clinical lecturer and honorary consultant cardiologist at the University of Sheffield, the 14 year gap between measuring fitness levels in 1971 and comparing these with heart rates in 1985-6 was “more than long enough to get unfit and unhealthy.” And Valerie Gladwell, senior lecturer in physiology at the University of Essex, added to this that there were just 54 men with a resting heart rate of more than 90 beats per minute. Gladwell: “In these individuals it may be their increased reactivity to unfamiliar situations rather than a high heart per se that may be increasing their risk.”
Source: British Medical Journal 2013;346:f2429