How Sleep Works
There's a five-stage sleep cycle, repeating throughout the night, that lasts from 90 to 110 minutes. Stage one is the lightest stage, when we're falling asleep. At stage two, brain waves slow and we drift into a deeper sleep. During stages three and four, we fall into the deepest and most restorative states. Brain waves slow to a crawl, and we're completely at rest. Finally, we move into the REM (rapid eye movement) stage, in which our breathing becomes rapid and shallow, our heart rate drops, and our eyes move quickly. This is when we dream.
It's the deep sleep -- stages three and four -- that we need most, and if your infant happens to cry while you're in deep sleep, rousing yourself can feel like trying to escape from quicksand. There's no easy solution, but trading off nighttime duty with a spouse can help. You both emerge a little sleep deprived, but neither of you is completely shot! The other gold-standard advice: sleep when the baby sleeps. It might be hard to tune out your racing mind and lie down with baby for an afternoon nap, but it's worth a try. Experts say your body responds to sleep deprivation by moving into the deep-sleep stages even faster than it normally does.