In mammals generally? Sorry, couldn't resist - in truth your question is good because while "sleep" is repeated endlessly, not just in the news but often by researchers who aren't controlling for photoperiod - that's NOT what the research says. It's light that's key, controlling the master hormone melatonin. Which is also a stunningly efficient antioxidant, of supreme use in taking out the garbage - something not irrelevant to Alzheimer's. If you sleep into the light regularly,long sleeps, your lifespan actually shortens.

Pretty much impossible to separate these days.