Inter- and intraindividual variability in daily resting heart rate and its associations with age, sex, sleep, BMI, and time of year: Retrospective, longitudinal cohort study of 92,457 adults.
Level 3 - non-randomized controlled study
Retrospective longitudinal cohort study without randomization.
PubMed 32023264 · doi:10.1371/journal.pone.0227709
What was done
Retrospective longitudinal cohort study analyzing 92,457 de-identified US adults from all 50 states who wore a wrist-worn tracker for at least 35 weeks between March 2016 and February 2018 (minimum 2 days per week, 20 hours per day). Data included a median of 320 days per individual and nearly 33 million daily resting heart rate (RHR) measurements to assess RHR variability and associations with age, sex, body mass index (BMI), sleep duration, and season.
What was found
Mean daily RHR was 65 beats per minute (bpm) across the cohort, with an individual range of 40 to 109 bpm (up to a 70 bpm difference between individuals). Mean RHR differed significantly by age, sex, BMI, and average sleep duration (exact effect sizes not reported in the abstract). RHR followed a seasonal pattern, peaking in January and reaching a minimum in July. While RHR remained stable within most individuals over the short term, 20% of participants experienced at least one week with an RHR fluctuation of 10 bpm or more.
Why it matters
Broad population reference ranges can obscure meaningful individual health changes because baseline resting heart rate varies widely between people but remains comparatively stable within an individual over time.
Limits
Specific numerical estimates, confidence intervals, and effect sizes for age, sex, BMI, and sleep duration are not reported in the abstract. The study relies on users of a proprietary commercial tracker, introducing potential demographic, socioeconomic, and health-behavior selection bias. Clinical diagnoses, medication use, and health outcomes were not described.
Cited by
- contradicts A resting heart rate of 60 beats per minute or below is required to fall into sleep and enter unconsciousness.