Supposedly, sitting for more than 5 hours per day contributes greatly to the risk of a heart attack, shortened life, etc. Is lying down just as bad?
Yup. That’s why I always sleep standing up.
Actual answer - I would imagine so. Common sense tells me that the reason 5 hours sitting causes problems is inactivity, and is not positionally motivated. Lying down would be at least as bad.
I have no cites for you, but the semiotics and anthropology professor on my committee once said, offhand, that while sitting is bad, either standing or lying down are fine. Something about not being bent at the waist was what’s crucial. Calcium deposition, flowing of humours, whatever.
She also wouldn’t let us scrape our chairs on the asbestos-tile floor.
What a spoilsport!