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High heart rate is risk factor for death, not just a sign of poor fitness, study indicates

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f2429 (Published 16 April 2013) Cite this as: BMJ 2013;346:f2429
  1. Zosia Kmietowicz
  1. 1BMJ

Danish 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.1

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 1985-6, 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.

They 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. But 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 rate in 1985-6 of between 51 and 60 beats per minute was associated with a 40% increased risk of death (hazard ratio 1.4 (95% confidence interval 1.1 to 1.9), when compared with a rate under 50, while a rate between 81 and 90 beats per minute doubled the risk (2.1 (1.4 to 2.9)) and one above 90 beats per minute tripled the risk (3.1 (2 to 4.8)).

The authors said that resting heart rate as an indicator of longevity had received a great deal of attention but that it has not been clear whether a high rate simply indicated low levels of physical fitness.

They concluded, “We found that irrespective of level of physical fitness, subjects with high resting heart rates 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.”

Tim Chico, senior clinical lecturer and honorary consultant cardiologist at the University of Sheffield, said that 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.” He added, “The message I take from this research is the importance of keeping fit as a lifelong habit. I often see patients who have previously been very fit. The important question is, ‘How fit are you right now?’”

Valerie Gladwell, senior lecturer in physiology at the University of Essex, pointed that there were just 54 men with a resting heart rate of more than 90 beats per minute. She said, “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.” The results may have differed if their heart rates had been recorded at the same time as their physical fitness was measured, she added.

Notes

Cite this as: BMJ 2013;346:f2429

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