Warming the body to its thermoneutral point is necessary for REM sleep, with both too much cold and too much heat impairing REM sleep duration.

“increase your bed temp from cool at the start & middle of night to warm (0-+2-3) toward morning and see if that doesn’t increase your REM %”

“Heating your bed/mattress/sleep environment for the 1-2hrs prior to waking really does seem to increase REM.”

“Also, heating your sleeping environment in the final 2-3 hours prior to waking can lead to dramatic increases in REM sleep.”

“You want your body temperature to increase slightly in the later phase of your sleep if you want to maximize REM”

“Just warming the bed toward morning has nearly doubled my REM (often 2hrs!)”

“And there are data to support the temp aspect of warm for REM, cool/cold for deep SWS.”

“See those two short waking bouts toward morning? Then heated the bed. Cold start of night, warm toward waking = big REM increase.”

“and in doing this it's allowed me to really optimize my sleep meaning I sleep much more deeply and I get far more rapid eye movement sleep than I ever did prior to using eight sleep”

“you also need to warm up to REM sleep but not too much if you take an organism or a human being and you strip them of bed sheets and strip them of clothes so they're basically almost on natural if you warm the body up to what we call the Thermon neutral point”

“if I keep you too cold I can reduce the amount of REM sleep if I get you too hot but I can imper the amount of REM sleep so it's a Goldilocks phenomenon not too little not too much just the right amount if I keep you there in terms of your thermal um net neutrality I can boost your RAM sleep”

“Warming your sleeping environment in the last two hours of sleep will dramatically increase the amount of REM sleep you get. I learned that trick from Matt Walker and it works spectacularly well.”