Health

How many heartbeats?

A few years ago someone told me that all mammals, including humans, have a lifespan of a billion heartbeats. I believed him, didn’t question the number, assumed that he knew what he was talking about. Some time later I decided to check the numbers, to work out how many heartbeats there might be in a human lifetime of 80 or 100 or 120 years. I was on a tube train and started with some calculations in my head – no room to use a pen and paper.

At rest our hearts beat at something like 60 or 70bpm (beats per minute). Top athletes might have a much lower heart rate. Back in the 1970s we heard that the great New Zealand runner John Walker had a heart rate of 40bpm. When I was a child my father’s was 48bpm. I have just tested mine and am surprised to find that it is only 58bpm; I thought it was higher than that.

To get a rough figure let’s use a bpm of 60. That makes 60 heartbeats per minute, 3,600 (60×60) in an hour and 86,400 (24×60) per day. You can round up or down to get approximate numbers for a week or a year after that: 7 x 90,000 makes around 630,000 heartbeats in a week; 50 x630,000 gives us around 30 million heartbeats in a year. At that rate you get through your first billion heartbeats in about 33 years. My heart has gone through more than a billion beats, and I’m well on the way to two billion. At these rates a person who lives to 100 will have had over three billion (3,000,000,000) heartbeats. Does your heart have a built-in limit like certain pieces of machinery? Can it go on beating four billion times or more, as long as everything else is working? I hope so.

Of course I had to take my calculations further and work out some figures on a spreadsheet, so here they are.

Heartbeats

Number of heartbeats (in billions) at age:

BPM

Per day

Per year

60

80

100

120

50

72,000

26.3m

1.58

2.10

2.63

3.15

60

86,400

31.5m

1.89

2.52

3.15

3.78

70

100,800

36.8m

2.20

2.94

3.68

4.42

80

115,200

42.0m

2.52

3.36

4.20

5.05

 

Age at which you reach

 BPM

1bn beats

2bn beats

3bn beats

4bn beats

50

38.05 years

76.10 years

114.16 years

152.21 years

60

31.71 years

63.42 years

95.13 years

126.84 years

70

27.18 years

54.36 years

81.54 years

108.72 years

80

23.78 years

47.56 years

71.35 years

95.13 years

With a heart rate of 60bpm you will get to 1 billion beats a few months before your 32nd birthday, and you’ll get to 3 billion beats just after your 95th birthday. If you want to live that long with a heart rate of 80bpm you will need your heart to beat 4 billions times. A billion heartbeats is not enough for most of us.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s