Exclusive: Fitbit's 150 billion hours of heart data reveal secrets about health

For something as important as heart health, it’s amazing how little you probably know about yours.

Most people probably get their heart rates measured only at doctor visits. Or maybe they participate in a limited study.

But modern smartwatches and fitness bands can track your pulse continuously, day and night, for months. Imagine what you could learn if you collected all that data from tens of millions of people!

That’s exactly what Fitbit (FIT) has done. It has now logged 150 billion hours’ worth of heart-rate data. From tens of millions of people, all over the world. The result: the biggest set of heart-rate data ever collected.

Fitbit also knows these people’s ages, sexes, locations, heights, weights, activity levels, and sleep patterns. In combination with the heart data, the result is a gold mine of revelations about human health.

Back in January, Fitbit gave me an exclusive deep dive into its 6 billion nights’ worth of sleep data. All kinds of cool takeaways resulted. So I couldn’t help asking: Would they be willing to offer me a similar tour through this mountain of heart data?

They said OK. They also made a peculiar request: Would I be willing to submit a journal of the major events of my life over the last couple of years? And would my wife Nicki be willing to do the same?

We said OK.

Oh boy.

About resting heart rate

Before you freak out: Fitbit’s data is anonymized. Your name is stripped off, and your data is thrown into a huge pool with everybody else’s. (Note, too, that this data comes only from people who own Fitbits — who are affluent enough, and health-conscious enough, to make that purchase. It’s not the whole world.)

Most of what you’re about to read involves resting heart rate. That’s your heart rate when you’re still and calm. It’s an incredibly important measurement. It’s like a letter grade for your overall health.

“The cool thing about resting heart rate is that it’s a really informative metric in terms of lifestyle, health, and fitness as a whole,” says Scott McLean, Fitbit’s principal R&D scientist.

For one thing — sorry, but we have to go here — the data suggests that a high resting heart rate (RHR) is a strong predictor of early death. According to the Copenhagen Heart Study, for example, you’re twice as likely to die from heart problems if your RHR is 80, compared with someone whose RHR is below 50. And three times as likely to die if your RHR is over 90.

Studies have found a link between RHR and diabetes, too. “In China, 100,000 individuals were followed for four years,” says Hulya Emir-Farinas, Fitbit’s director of data science. “For every 10 beats per minute increase in resting heart rate, the risk of developing diabetes later in life was 23 percent higher.”