[brlewis]

Did you click the "Article Continues" button?

"Fitbit’s data confirms a lot of what cardiologists already know. But because the Fitbit data set is ridiculously huge, it unearthed some surprises, too."

From there the article goes on to list a number of new insights and potential research areas to pursue.

From a screenshot at https://www.cnet.com/how-to/count-steps-with-apple-watch/ the Apple Watch privacy settings let you turn step count and heart rate tracking on and off, but don't let you choose whether or not to upload them.

[blub]

I did, none of the "surprising things" seem like they could result in any medically actionable info. They're more like medical curiosities, while the truly actionable info was already known.

iCloud sync can be turned off completely on any iPhone. Anyway, I believe the health data is encrypted with some device-specific secret, but I'm not 100% sure.