Alcohol, Sleep, and Why You Might Re-think that Nightcap

"Alcohol makes you sleepy."

We've all heard it. Many of us have experienced it. A few of us even swear by it—enough to ceremonially partake in a glass or two of wine before crawling into bed.

A nightcap.

In fact, a little booze has been experimentally (and anecdotally) demonstrated to help us fall asleep faster and increase slow-wave, or deep, sleep in the first half of the night.

But its effect on other aspects of sleep—notably, the second half of the night—leaves much to be desired.

What causes alcohol's strange and dichotomous effect on the sleeping brain? And the real question—do you accept the nightcap or not?

Sleep Cycle App: Precise, or Placebo?

Thanks to the Internet, it's the age of self-diagnosis. People like to learn about (and treat) themselves through technology.

Especially when pretty graphs are involved (see fancy screenshot at right).

As a sleep researcher, I was interested in my friends' use of sleep-tracking apps, and I received a pretty positive response when I prompted them for their thoughts:

"I'm a believer."

"When I use it right, I feel less groggy."

The website sleepyti.me and smartphone apps like Sleep Cycle use the average human's sleep pattern to determine the best window of time that you should wake up. The idea is that interrupting the "wrong" sleep cycle stage, such as slow-wave ("deep") sleep or REM (rapid eye movement, when dreaming occurs), results in grogginess upon awakening, as many of us can attest. Sleep researchers call this phenomenon "sleep inertia."

It's such a big deal that, in the sleep laboratory, we as techs are instructed not to wake participants if they're in REM, even if the experimental recording time is over.

So when a friend told me that he only feels refreshed after (according to his sleep-tracking app) eight REM cycles, I got a little skeptical, given the average person will only experience four or five REM periods per night.

What's the verdict on sleep-tracking apps? How do they work, and how accurate are they? Is it all a big scam, or perhaps the placebo effect at work?