Hey Steve_James,
Thank you for using Apple Support Communities!
It looks like you're not getting the right health data in the Health app while sleeping. We want to help get that corrected for you.
Try testing the personal data you've input into the app to be sure everything is reading accurately: Use the Health app on your iPhone or iPod touch.
Try force closing the Health app: How to force an app to close on your iPhone, iPad, or iPod touch
Have you restarted since you noticed the issue? Restart your iPhone, iPad, or iPod touch
Cheers!