30-day Sleep Challenge: What is good sleep hygiene exactly?

Twin Cities wellness coach Amy Mattila likes to say that "your habits make your life."

We'll put that to the test this week. For our Snooze Goal we're going to focus on "sleep hygiene," a set of prescribed habits that help us sleep well. We'll also look at the science behind these seemingly simple habits.

Over the next seven nights, try at least one of these recommendations from local sleep experts. Your sleep diary will give you clues about which ones might make the most difference for you, so take it out to pinpoint your interruptions and issues.

Keep it dark: When our eyes are exposed to light, it stimulates a nerve pathway to parts of the brain that control hormones, body temperature and other functions that impact how awake we feel. Darkness is key to regulating our biological clocks. It tells our body that it's time for bed, and if we wake in the middle of the night, it signals that it's still time for sleep.

• Dim overhead lights or switch to softer lamplight in the hours before bedtime.

• Prepare a dark bedroom, with blackout curtains that block moonlight or shining street lamps.

• Keep digital devices or clocks more than an arm's length away so that you aren't tempted to look at them when you wake in the middle of the night to check the time and start calculating how much time you have left to sleep. That's what Sleep Health Specialists' Sarah Moe calls "panic math."

• Moe also suggests an old-school sleep tool: "Everybody should wear an eye mask at bedtime," she said. "It'll take two or three days to get used to, but once your body is used to having something on your face, it is so helpful."

An eye mask can help in several ways. With time, just pulling the mask over your eyes can trigger your body to say, "Oh, this means it's time to go to bed," Moe said. It also can help you fall back asleep faster if you wake up during the night.

"If you're wearing an eye mask, you will open your eyes and not be able to re-engage with your environment because you'll have that mask on," Moe said. "When we do open our eyes, there is a little moonlight exposure. There's electronic devices exposure. [It could be a] very small percentage of light, but there's still exposure and the ability to re-engage with our environment, which turns our brain on."

Keep it cool: Lowering the thermostat at night (to between 60 and 67 degrees, according to the National Sleep Foundation) can improve your sleep. Our bodies' natural evening surge in melatonin, a hormone that helps regulate the timing of when we sleep, is triggered not only by the darkening sky, but by the drop in core temperature that happens with the setting sun, explains Matthew Walker in his book "Why We Sleep: Unlocking the Power of Sleep and Dreams."

Because our core temperature can be regulated by the surface of our skin, taking a warm bedtime bath can also help tell our bodies that it is time to sleep. A hot bath brings blood to our skin's surface, radiating out inner heat and causing our core temperature to fall.

Keep screens away: One or two hours before bedtime, put away your phones and tablets. The blue light they emit can delay your ability to fall asleep. What's more, it can cause you to wake up in the middle of the night.

"The blue spectrum of light is actually somewhat uncomfortable in a sort of a primitive way to the brain," said Dr. Conrad Iber, a pulmonologist and sleep expert with M Health Fairview. "It's sort of like caffeine — it awakens you and it delays your sleep time. So it's a real bad actor."

A 2018 Brigham and Women's Hospital study found that people who read using an iPad before bedtime had both suppressed levels of the sleep timing hormone melatonin and fell asleep later, compared with those who read a print book.

Blue light also can affect the quality of our sleep, according to Moe. "It remains in our neurological system throughout the night, causing what we call spontaneous arousal or awakening," she said.

While blue light blocking glasses (even semi-cute ones) abound these days, many experts don't necessarily recommend them, in part because there haven't been enough large studies on how effective they are. They maintain that skipping blue light before bed is the best practice.

"If we're drinking caffeinated beverages all day, when we attempt to initiate sleep, adenosine isn't getting released, and we're not able to fall asleep," she said. That's why Moe suggests cutting off any caffeine around 2 p.m. if you are aiming for a 10 p.m. bedtime.

Iber often counsels people to stick to a simple rule to avoid caffeine in your brain at night: "No more than three, and none after three," is his motto.

Alcohol also can be a troublemaker. It's a sedative, which can help bring on sleepiness. Then, "when the liver metabolizes out the alcohol, one to two hours later, the rapid withdrawal of the sedative results in the alerting of the brain," Iber said. "And so what you're doing is you're actually creating the nighttime awakening."

Alcohol can also suppress REM sleep, said Moe, who suggests limiting evening imbibing to a single drink.

If rich or spicy foods trigger indigestion, this can also make it difficult to fall asleep or cause you to wake up in the middle of the night.

Follow a bedtime routine: Before bed, doing the same calming things — in the same way and at the same time — tells our brains that it's time to sleep. Just like kids, adults respond well to the basics: bath, book, bed.

Mattila gives her clients a few more suggestions for what she calls a "wind-down," including getting into relaxation clothes, having caffeine-free tea, and using calming essential oils like lavender.

Moe suggests thinking about preparing for bed like landing a plane: A half-hour or hourlong bedtime routine can help you begin your descent.

"When people are at work throughout the day, that's just like when you're flying through the air. And when we land our plane, we don't land by dropping out of the sky, we land by descending," she said. "We don't go to bed by dropping out of the sky. We don't fall asleep by going, going, going and then getting into our bed and thinking 'Boom, now it's time to land.' "