I wonder what "needs" means, though. As I get older, my body just naturally sleeps fewer hours than when I was younger, and there seems to be nothing I can do to change that. I don't use an alarm clock, I go to bed at around the same time every night, I don't consume caffeine after noon, etc. When I wake up in the morning, I feel awake, and it's almost impossible for me to fall back asleep, even if I continue lying in bed with my eyes closed.

So, scientists may say I "need" more sleep, but what of it? I can lie in bed awake feeling bad about that, or I can get out of bed and do things with my extra time every day. I try to live a healthy lifestyle, and I would definitely sleep more hours if I could, but I've followed every suggestion, and my body just does what it wants. My impression is that this is a common experience.