The American Heart Association considers a resting heart rate [RHR] of between 60 and 100 beats per minute [bpm] to be normal for adults.
However, a recent study concluded that when it comes to comparing people’s heart rates, “normal” does not actually exist. Although most adults have RHRs that are relatively stable over time, rates between healthy individuals can vary by as much as 70 bpm.
The researchers had access to data from well over 92,000 adults across all 50 states, each of whom wore a heart rate monitor at least two days each week for a minimum of 35 weeks. The data provided about 33 million daily RHR values.
They found that while the overall average RHR was 65.5 bpm [plus or minus about 8 bpm], the minimum and maximum RHRs recorded among individuals were 39.7 and 108.6 bpm, respectively. In other words, when all participating adults were compared, their “normal” heart rates could vary by around 70 bpm.
Other interesting findings included:
• On average, men’s RHRs ranged between 50 and 80 bpm, while those of women averaged slightly higher, between 53 and 82 bpm.
• When adults of different ages were compared, average RHR increased steadily until reaching its peak at age 50, then began to slowly decline.
• Among all adults participating, the scientists found that the lowest RHRs occurred in people who got an average of 7 to 7.5 hours of sleep each night.
• Individuals with moderate body mass index [BMI] measurements tended to have lower RHRs than those with low or high BMIs.
• RHR tended to fluctuate with the seasons among participants by an average of 2 bpm, peaking in January and reaching its lowest level in July.
Because an estimated 20% of U.S. adults now own a smartwatch or fitness band capable of continuously monitoring their heart rates over a long period, it makes sense to use this data to its full potential, the researchers said.
They expressed hope that in the future, health professionals might use RHR data to help diagnose conditions such as cardiovascular and pulmonary diseases in their early stages, and even provide insights into reproductive health.