Well, this is silly but I recall hearing a medical explanation about why people tend to wake up around 3AM - but I can't remember what it was -- if it has to do with digestion, or circulation, or hormonal levels...I don't recall. But, I often wake up at 3AM to kick off the covers. Over the years I assumed it was something about how our thermostat was set, but we have lived in several different houses, so the thermostat really can't be blamed. (I'm 43 and this has gone on for years, so I'm not menopausal)