If you have an interest in sleep (and how to get better sleep), I highly recommend this book called Why We Sleep: The New Science of Sleep and Dreams by Matthew Walker. It blew my mind the kind of research they've been doing on sleep and how it affects us human beings. I now put a much higher priority on getting enough sleep each night.
Totally @chernern, my husband recently read research that links lack of sleep to dementia and began to really prioritise his sleep.
They discovered the brain shrinks when we sleep, opening up lymph pathways in the brain that remove the waste products of brain cell combustion. Without this we literally die, one brain cell at a time.