Why heart rate decreases with age

Washington – Researchers have tried to look into the age-old question as to why maximum heart rate (maxHR) decreases with age.

According to researchers at the University of Colorado, this decrease in maxHR not only limits the performance of aging athletes but it is also a leading cause for nursing home admittance for otherwise-healthy elderly individuals who no longer have the physical capacity required for independent living.

We say we’re just getting old and slowing down, but exactly what is it that is slowing down?

Everybody knows that aerobic capacity decreases with age. You know that chart in your gym that shows your target heart rate decreasing as you get older?

Well, that’s not a senior discount to let the elderly get off easy on their treadmill workouts. It’s because older hearts simply can’t beat as fast as younger hearts.

So the older person who’s doing 120 beats per minute is probably working harder — at a higher percentage of maximum heart rate — than the younger person who is at 150 beats per minute.

A new study by a group led by Catherine Proenza, PhD and Roger Bannister, PhD from the University of Colorado School of Medicine reports that one of the reasons for the age-dependent reduction in maximum heart rate is that aging depresses the spontaneous electrical activity of the heart’s natural pacemaker, the sinoatrial node.

Like most initial discoveries in basic science, this study opens many more questions and avenues for further research. But the significance of the study is that it raises the possibility that sinoatrial ion channels and the signaling molecules that regulate them could be novel targets for drugs to slow the loss of aerobic capacity with age.

Proenza notes that “although maximum heart rate goes down for everybody equally, regardless of physical conditioning, people can improve and maintain their aerobic capacity at all ages by exercising.”

This study is set to be published in the journal Proceedings of the National Academy of Sciences of the United States of America.