With many people still staying home and our daily schedules constantly changing, Fitbit took a deeper look at how this experience is impacting Fitbit users’ resting heart rate.
Resting heart rate is the number of times your heart beats per minute when you are still and at rest. This metric can be an important indicator of your fitness level and overall heart health. Not only can it be used to track your fitness level, but it can also alert you of potential health issues such as illness, high stress levels, sleep deprivation, dehydration, overtraining, and underlying medical conditions.
What Fitbit discovered is encouraging: across the US, when comparing the baseline data from January to that of February, March, and April, the resting heart rate improved, which means that it declined, for the general population, skewing more so for younger users. They also looked at international data, which saw similar trends.
In March, resting heart rate began to decline across the country; the effect nearly doubled month over month in April, when the average resting heart rate dropped by 1.26 beats per minute in users aged 18 through 29, which may not sound like a lot, but is a statistically significant change. In fact, users across all age groups saw a decline. There were no significant geographical variations.
To better understand how their users’ lifestyle behaviors may be impacting resting heart rate, they took a deeper look at measures like active minutes, sleep time, and bedtime variability. After all, at a time when people are largely stuck indoors, they’ve seen that physical activity, like average step count, has declined, which could lead to an increase in resting heart rate. However, they’re seeing the opposite, though, which is great news, but they knew there had to be more factors at play here.
Step counts declined, but active minutes increased. Although step counts are down across all age groups, 42 percent of people have increased their active minutes and 31 percent have continued to maintain their same average level. This indicates that people moved from gaining incidental steps throughout the day to more vigorous walks that get their hearts pumping. For example, we may not be getting our steps in during our daily commutes, but we are going on walks and hikes to earn those active minutes and keep our hearts healthy.
In the figure above, we can see that users who increased their median daily active minutes experienced a larger decline in their resting heart rate.
Sleep duration increased during shelter-in-place. In fact, 45 percent of people have increased their sleep time, while 30 percent have maintained their average sleep duration. This is great news, especially because not getting enough sleep can have a negative impact on resting heart rate. Not getting enough sleep is a risk factor for cardiovascular disease.
On average, users who increased their sleep duration the most experienced a larger improvement in their resting heart rate.
Bedtime variability decreased. During normal times, people (particularly young people) tend to go to bed later on the weekends, often leading to social jet lag, which can impact heart health. Not only are people going to bed earlier on the weekends since they are no longer going out, but they are also going to bed later on the weekdays, leading to a more consistent bedtime. Data shows that over 40 percent have reduced their bedtime variability by at least 15 minutes.
On average, users who decreased their bedtime variability the most experienced a larger improvement in resting heart rate from January to April.
Fitbit also observed that users who exhibited multiple healthy behaviors saw a larger decline in resting heart rate. Here is an example:
For all age groups, the users who increased their active minutes by more than 30 minutes a day and slept an additional hour experienced a larger decrease in resting heart rate than the ones who made only one of those two behavior changes.
As you can see above, younger users from many countries experienced the largest decline in resting heart rate and, across age groups, Spain, India, Mexico, France, and Singapore saw the biggest improvements. The population of Sweden, a country that did not have a shelter-in-place lockdown enforced, did not experience resting heart rate improvements, while most age groups in Australia experienced smaller or no improvements when compared with other countries.
One factor that could have played a role is seasonality, the typical lifestyle changes that go hand-in-hand with the changing seasons. Resting heart rate is known to have a minor seasonal trend, with slightly higher rates in January and slightly lower rates in July. In order to quantify the impact seasonality had on the observations we made, they picked another cohort of users from January 2019 and observed them through April 2019, and found that the improvement in resting heart rate in 2020 is 2.4 times bigger than that of 2019!
There’s an expectation for active minutes to increase and bedtime variability to decrease from January to April anyway, but the differences observed in 2020 so far are more dramatic than last year. What is the most striking? Behaviors like sleep duration and step count do not follow the typical seasonal pattern this year. Generally, sleep duration decreases, and step count increases in April compared to January. It was the opposite this year, with users sleeping more and taking fewer steps in April.
Overall, Fitbit’s findings on resting heart rate were hugely encouraging, and they’re happy to see their users are adapting their behavior and still prioritizing their health and fitness. During these trying times, it’s definitely something to celebrate.
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