
Variability in resting heart rate: association with age, sex, sleep&BMI (2020) - bookofjoe
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0227709
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lawlorino
I found the seasonal variation really interesting, to summarise on average
people's resting heart rate is ~2bpm higher at the start of the year than it
is in July. The authors don't hypothesise why this is, my guess would be
general unhealthy behaviour like excess eating, sedentary behaviour and
alcohol consumption around the Christmas period (population was from the US),
but it could also be colder ambient temperatures.

It'd be interesting to try and control for this e.g. see if this phenomenon is
also present in non-Christian majority countries, or Christian countries
within the tropics where the annual temperature variation is smaller, but on
average higher than most of the US.

