That's what was unclear about the article for me. The recommendation is 8 hours, but under 6 hours is considered sleep deprivation. So... there seems to be a

That's what was unclear about the article for me. The recommendation is 8 hours, but under 6 hours is considered sleep deprivation. So... there seems to be a wide amount of flexibility between 6 and 8 hours, and it's likely person-dependent. Perhaps there's deleterious effects below 8 hours for everyone, but once you're at ~6 hours or below, the negative impact increases significantly.