A high heart rate is a risk factor for death, not just a sign of poor fitness.

Researchers have said that a high heart rate may be an independent risk factor for mortality, after finding that men with higher rates were more likely to die even if they were physically fit.

The researchers tracked the health of just under 3000 men who were part of the Copenhagen Male Study, set up in 1970 to monitor the cardiovascular health of men aged 40 to 59 years at 14 large companies in Copenhagen.

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 1985-86, when the men’s mean age was 63, just under 3000 of the original participants underwent a further check-up, which included measurements of height, weight, blood pressure, blood fats, and blood glucose. Their resting heart rate was also recorded.

In 2001, the researchers checked national Danish registers and found that just over a third (1082) of the men had died. The researchers found that a high resting heart rate was associated with lower levels of physical fitness, higher blood pressure and greater weight, and higher concentrations of circulating blood fats.

Similarly, men who were physically active tended to have lower resting heart rates. However, the results 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 in 1985-86 of between 51 and 60 beats per minute was associated with a 40% increased risk of death.

Source: BMJ 2013;346:f2429.