The Sleep Calculator is more than just a guide to set your alarm clock. It takes your planned wake-up time, accounts for the time it takes you to get to sleep, plans out your rest in 90-minute natural sleep cycles, and lists your optimum time to go to bed so that you wake up refreshed.
The difference here is that in sleep cycle theory, periods of sleep activity in the brain manifest in an average duration of 90-minute cycles, with those broken down into 15-minute cycles too. If you wake up in the middle of a sleep cycle, you're more likely to be disoriented and groggy. Conversely, if you wake up smoothly at the end of a complete sleep cycle, you will feel more refreshed and alert.
At least that's the theory, which is well-supported. When it comes to sleep research, the best we can usually hope for is "close enough."
The Mystery of Sleep
Sleep is one of the most perplexing biological functions known to science. Sleep research produces new findings all year 'round. Sience does not know exactly why we sleep, what happens when we do, why some people get by on four hours' cat nap while others need a ten-hour hibernation. We also haven't pinned down why we dream or how we do it.
It's challenging to monitor sleep in a laboratory since volunteers have to come in, get wired up to all kinds of sensors, and try to fall asleep in this foreign, clinical setting. However, the most we can tell with the latest technology and techniques is as follows, as per the American Academy of Sleep Medicine.
We do know that sleep - or lack thereof - has a profound impact on physical and mental health. The quality of sleep matters as much as the quantity. Again, some people can nod off in a diner booth and get in a quick nap, while others need a completely dark room, complete silence, and absolute solitude or their sleep suffers.
As of this writing, a recent discovery has been about blue light. It seems melatonin, the hormone in the brain which regulates sleep-wake cycles, is affected by exposure to blue light specifically because it mimics a blue, daytime sky.
Recent mobile devices such as phones and tablets have come with a blue light filter that is set by default to kick in around sunset so that browsing a phone at night doesn't interfere with going to sleep.
Sleep Cycles Mapped
Sleep is divided into two phases, REM and non-REM. REM (Rapid Eye Movement) is said to be the phase where dreaming occurs. When first falling asleep, non-REM occurs first and then a transitional period, which is called slow-wave sleep. During this time, the body's processes slow down.
After this period comes a period of REM sleep, where brain waves speed up and body processes accelerate. Finally, the REM period ends and the stage proceeds back to the non-REM stage, lasting about ten minutes before another plunge into REM begins.
The above process takes an average of about 90 minutes to complete a cycle, hence the calculator. Studies have shown that interrupting a sleep cycle can lead to "sleep inertia," a state of impaired cognitive and sensory-motor performance.
In addition, the human body has a natural circadian rhythm throughout the day. Starting from your normal wake time, it takes about thirty minutes for all biological systems to come fully up to daytime levels - blood flow, reflexes, digestion, and cognition are all affected. Throughout the day, it's natural to have a peak around the late morning to early afternoon hours. This is often followed by a small lag in energy in the afternoon followed by a second period of peak energy. This period lasts from afternoon until mid-evening, when the body's processes begin to wear down again.
Much of this activity is affected by levels of light and the timing of sunrise and sunset. Some suffer from Seasonal Affective Disorder, which makes them extremely sensitive to light exposure over the seasons. In the dead of winter, they'll feel depressed, lethargic, and drained, while in the peak of summer they'll be too manic and over-agitated.
In the brain's neurochemical system, several natural chemicals in the body play a role in sleep:
• Glycogen - the principle glucose from which humans and other mammals produce energy - depletion of this signals the need for rest.
• Adenosine - a neurochemical that builds up in the brain as exhaustion increases, and is removed from the brain during sleep.
• Caffeine - we all know this as the wake-up drug, which actually functions by blocking adenosine receptors in the brain.
• Melatonin - the hormone we've discussed here, which is naturally produced by the body and serves to regulate sleep and wakefulness.
Bad Sleep Hygiene
While we may enjoy the many benefits we get from modern civilization, it comes at a sharp tax to our sleep quantity and quality. Having 24/7 lighting available indoors all night deregulates our biological rhythms, as does our tendency to stare at glowing screens late into the night.
Jet travel interferes with our circadian cycles too, since the human body did not evolve under conditions of being able to travel to the other side of the planet in a few hours. And of course, our rampant dependency on caffeine in coffee, pop, and energy drinks doesn't help.
Sleep deprivation is tied to a number of negative health effects, not the least of which is a shorter life expectancy due to cumulative sleep deprivation. In the short term, it can lead to decreased attention, memory, and cognition, while increasing the appetite, leading to weight gain.
Sleep disorders are tied to mental disorders including depression, anxiety, stress, seizures, dementia, and personality disorders.
Practicing Good Sleep Habits
As stated above, sleep research is a steady ongoing process. But according to the present general consensus, these are the things you can do to ensure the greatest shot at healthy, natural sleep:
• Stay regular - Don't sleep in on weekends. Set a time to go to bed and a time to wake up and stick to it. Your brain benefits far more from a consistent sleep schedule than it does from extra sleep on some days.
• Hold off electronic usage a half hour before bedtime - This covers phones, TV, computer, and all. It is tempting to want to watch TV or read the Internet until you feel sleepy, but you're actually delaying the sleep process.
• Minimize caffeine and alcohol - Both interfere with natural sleep processes.
• Midday naps are OK - If you find yourself feeling groggy in the midday, consider a 20-minute nap over a cup of coffee. In the long run, you'll have much more energy later. Some people are just wired for a midday nap.
• Have a good sleep environment - Your bedroom at night should have a slightly cooler temperature than in the daytime, be as dark as possible, and free of noise except for "white noise" from a fan or similar device.
And of course, use our calculator! Experiment with the right patterns that work for you, as everybody has slightly different needs. Pleasant dreams!