Week 2: Stages of a Good Night’s Sleep

We know we are supposed to get a good night’s sleep. But what exactly does that entail? Sleeping through the night? Not being woken up by an alarm (Yeah, if you don’t work for a living!)?

The first step is falling asleep, which should take (on average) between ten and thirty minutes, says Joan Fox, MD, a sleep medicine specialist at the Minnesota Sleep Institute. “If you are out like a light, it means you are sleep deprived; if it takes you longer than that [thirty minutes], something is getting in the way.”

Once you are asleep, there are four stages that our bodies cycle through during the night, says Michael Alter, MD, a sleep medicine specialist with HealthPartners Specialty Center, Fairview Lakes Sleep Center, and the Sleep Center at the University of Minnesota Medical Center.

+ Stage One: Light sleep. Alter calls this stage the transition period, the time from between falling asleep and stage two. This stage comprises 5 percent of your total sleep for the night.

+ Stage Two: Still considered light sleep, this stage, which is a little deeper than stage one, takes up approximately 50 percent of a night’s sleep.

+ Stage Three: Slow wave, or deep sleep. This accounts for 15 to 20 percent of sleep.

+ REM (Rapid Eye Movement): This is the last stage of sleep, during which we dream. REM comprises 20 to 25 percent of sleep.

Though these percentages are chunks of time, “you don’t stay in one stage for 15 or 20 percent all at once,” Alter says. “You cycle through the sages (one, two, three, REM), which takes approximately ninety minutes. We go through about five stages a night.”

And though we cycle through the stages, these cycles are not all equal. “Dream sleep lasts longer in the latter half of the night,” Fox says.

Once you have had a full night’s sleep, “some people will feel refreshed and alert, and others may take a few minutes before they feel refreshed,” Alter says. “We often will use the simple question, do you use an alarm clock to wake up? If yes, there is some element of sleep deprivation, even if it is mild. If an alarm clock is waking you up, you are not waking up on your own, [which means you probably need more sleep].”