Understanding the 5 stages of sleep

The entire process of sleep may sound simple: you crawl under the covers, flick off the light and, within a few minutes, you’re asleep. Every fiber of your body is at rest.

But for decades, sleep has baffled scientists as they’ve sought to understand why we need sleep, and why the quality of our sleep can turn us into pussycats or roaring lions the next day.

They’ve studied dreams, and we and our therapists analyze our dreams.

On any given night when millions of people are sleeping soundly, millions more toss and turn and fidget, trying to finally get to sleep. Some even stop breathing for a few seconds several times while they’re asleep – a condition labeled “sleep apnea.”

But while we may think our bodies are at complete rest, the exact opposite is true.

Sleep’s five stages

There are five stages of sleep, and your body progresses through each of the stages and then back to stage 1.

For many people, their quality of sleep in all of the stages is affected dramatically by everything from a caffeinated cola downed at 2 in the afternoon to that after-dinner cigarette or alcoholic “nightcap” to diet pills, decongestants, antidepressants, and other over-the-counter and prescription medications.

When the cycle begins at stage 1 when you first climb into bed, your eyelids start to get heavy and you feel yourself nodding off. Appropriately enough, this stage is called “drowsiness.”

You stumble into stage 1 when you first fall asleep, and you’re there for no more than five minutes, 10 minutes tops.

You don’t know it, but your eyes move slowly under your closed eyelids. Muscles that helped you make it through the day and most of the night will start to wind down.

This is the stage where the slightest sound -- your mate coughing softly, your cat playing in the next room, the sound of something dropping in the other end of the house -- will wake you. You may even get that feeling that you’re falling, and you may jump, like you do when somebody startles you.

Morphing into stage 2

If you don’t wake up, your sleep morphs into stage 2, your “light sleep.” Your eyes stop their hidden movements, your heart stops beating as quickly, your temperature decreases slightly, and your brain waves begin to slow punctuated by bursts of rapid waves, the “sleep spindles.”

Then, you’re in La-La Land, or what sleep experts call the “deep sleep” of stages 3 and 4. Nothing short of a bulldozer crashing through your bedroom will wake you. And if something does startle you from your slumber, you wake up, groggy and wondering where in the heck you are -- but only for a few minutes.

In stage 3, delta waves -- extremely slow brain waves -- appear, punctuated by smaller, faster waves. In stage 4, it’s nothing but delta waves.

It is in these stages that children wet the bed, scream out in night terrors, and walk while fast asleep.

The REM stage

Seventy to 90 minutes later, you enter the stage known as Rapid Eye Movement sleep, more commonly called REM sleep. Your eyes dance rapidly under your eyelids as night progresses and you fall deeper -- and deeper -- asleep.

Dreams -- the good and the ghoulish -- explode from your subconscious, and the muscles in your arms and legs become immobile. You begin breathing rapidly and irregularly.

The beating of your heart picks up steam, your blood pressure rises, and your brain as active as it is when you’re fully awake.

If, by some chance, you’re awakened during REM sleep, you’ll tumble back into REM, not start the sleep stage from scratch.

Your infant will spend about half of his or her time in REM sleep. Your older kids -- and you -- generally spend half of your time in stage 2, and about 20 percent in REM.

And then morning comes.

Depending on the quality of sleep you’ve just experienced, you’ll either want to fight the Roman army and slay the day’s dragons, plod through the day like a caffeinated zombie, or crawl back under the sheets for some more shut-eye.

The latter two are what sleep problems and quality-of-life issues are made of. These are the problems, such as sleep apnea, that drive most people to doctors and sleep specialists.