If that's the only factual information worth taking away from the book, then what is the point of the book? I have plenty of anecdotal experience to suggest tha

If that's the only factual information worth taking away from the book, then what is the point of the book? I have plenty of anecdotal experience to suggest that sleep impacts my health already. A book that uses questionable data to back up something I can observe directly seems to have absolutely no utility.