Dr. Rhonda Patrick: I was wondering if you had any tips on some more advanced types of sleep hygiene. We all know dark, cold, and quiet.

Dr. Michael Grandner: Rocket science.

Dr. Rhonda Patrick: Exactly. But are there more advanced sleep-hygiene techniques? Maybe something involving resting heart rate, respiratory rate, or another unconventional measure?

Dr. Michael Grandner: What useful advice might not appear on the first page of sleep-hygiene results? One recommendation you'll often see is to keep a regular schedule. The brain loves predictability. If you keep a regular schedule, time itself becomes a cue.

If you want to eat lunch at noon every day, start eating at noon, and your body will learn to get hungry at that time. But what if you can't keep a regular schedule? Find other ways to build predictability into your sleep.

I work extensively with Major League Baseball. During the season, players are constantly traveling, competing in different time zones, and sleeping in different hotels. How do you maintain regularity when you're always moving? For people whose lives are like that, stop trying to keep a regular schedule and build predictability in other ways.

Create a highly predictable nighttime routine. Do the same things in the same order, even in a different place or hotel room. Bring familiar items with you, such as a pillowcase that acts as a conditioned stimulus. Use the same toothbrush whether you're at home or on the road. If you travel often, repeat the same sequence even when the time or place changes. Find other ways to build predictability when time itself isn't predictable.

Another recommendation is to avoid bright light at night. What if you can't? Blue-blocking glasses can help, but they usually need to be orange or red. Some yellow or brown lenses will work. If you can put them on, look at something blue, and still identify the color, they won't do the job from a circadian perspective. Some lenses block blue light to reduce eye strain, but that's different.

If you put on orange-tinted glasses and can't see the color blue, then environmental light isn't going to interfere with your sleep in the same way because it's not going to send a daytime signal.

Fewer people know that bright morning light can help set up nighttime sleep in three unconventional ways.

First, a regular morning time and a strong daytime signal start a clock. I'm talking about daylight and outdoor light, not just turning on a bedroom light. Indoor light is a couple hundred lux, while outdoor light measures in the thousands of lux.

That strong daytime signal anchors the clock when it arrives at a predictable morning time. Just as you'll get hungry a certain number of hours after a meal, a strong and predictable morning light signal means that your body will expect to be ready for sleep about 16 to 17 hours later.

Making that time more regular is like throwing a ball downfield. If you throw it about the same distance each time but keep moving, the person downfield doesn't know where to stand. If you stay still, they can predict where the ball will land. A regular morning signal starts that timer and sets you up for success.

Second, morning light creates circadian amplitude. Your circadian rhythm is a 24-hour cycle. If you're on the couch in the dark all day, you don't have a strong daytime rhythm, so you won't have a strong nighttime rhythm. Being active and getting outdoor light, especially in the morning, creates a strong daytime signal and an even stronger nighttime signal.

Third, light exposure across the full day matters. Light at night is disruptive, and light in the morning is beneficial, but the daytime pattern also matters. The more outdoor or bright light you get during the day, the more it inoculates you against light at night.

With a strong daytime light signal, nighttime light from screens may have less effect for most people. Because the circadian system already knows where it is in the daily cycle, it isn't searching for more timing information. It can disregard a conflicting signal instead of interpreting nighttime light as daytime. Plenty of daytime light can make you more resilient to nighttime light.

Dr. Rhonda Patrick: That's fascinating. I've noticed that when I'm traveling and spend the day outside, the lack of my usual dim hotel lighting doesn't matter because I'm exhausted after being outdoors.

Dr. Michael Grandner: For most of our existence, humans lived with equatorial bright days, dark nights, and relatively little seasonal variability around the Mediterranean and nearby regions. We solved many problems by creating walls, buildings, and artificial light, but we also created new ones. We're still running the same biological code.

Dr. Rhonda Patrick: I have a couple of follow-up questions. Does the timing of morning light matter? Should you go outside as soon as you wake up? How long should you stay outside? Thirty minutes?

Dr. Michael Grandner: Morning light is key, and earlier is better. About 15 minutes may be enough, while 30 minutes may be better. A morning walk or run is ideal.

Morning light does more than provide a daytime signal. It also affects melatonin, which we'll discuss when we talk about supplements. Your natural melatonin falls from its morning peak to almost nothing. Light naturally suppresses melatonin, so exposure while the level is still high accelerates that decline.

Dr. Rhonda Patrick: It's like coffee.

Dr. Michael Grandner: In a way. This is also why I recommend waiting an hour after waking before using caffeine. Immediately after waking, the amount of adenosine available for caffeine to block is still very low. You haven't produced enough for caffeine to have much effect.

If you drink caffeine as soon as you wake up and feel more alert, your sleep inertia is probably fading while light suppresses your melatonin. You may attribute those effects to caffeine even though you probably would have felt mostly the same without it. The caffeine still has effects later, but you've missed its peak. Time it a little later.

Dr. Rhonda Patrick: You're saying you want to use the caffeine when you need it more, such as when you're working and adenosine has built up.

Dr. Michael Grandner: Yes. Adenosine builds across the day and is at its lowest level when you wake up. Caffeine works mostly by blocking adenosine, so why block it when there isn't much available? Wait until it accumulates a little.