How to Conduct a Personal Experiment: Biphasic Sleeping

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Updated on August 12, 2013

It’s time for another edition of “How to Conduct a Personal Experiment.” Last week, it was the cold water plunge. Today, we’re going to talk about running a biphasic sleep experiment. First, though, I’d like to know: how are the cold plunges going? Are they, well, cold? More importantly, did you have any difficulties setting up the experiment, identifying variables, and choosing what to measure and track? This whole personal experiment stuff is likely new to most of you, and while there’s no real “wrong” way to go about it, there will be some initial difficulties. Be sure to keep us posted in the comment section.

Okay, on to the new experiment.

Biphasic sleeping is exactly what it sounds like – two-phased sleep. Instead of monophasic sleeping, which is sleeping in one big unbroken block of time, biphasic sleeping is broken up into two chunks of time. I wrote about biphasic sleeping last year, explaining how considerable evidence suggests that biphasic sleeping is actually the natural sleep pattern in humans. Before the Industrial Revolution, back when darkness meant bedtime and keeping the light on after dark required the consumption of expensive candles and lamp oil, people had far more exposure to darkness. They didn’t have iPhones, laptops, big screen TVs, or even lightbulbs. They had the moon, the stars, the campfire, or maybe – if their city had implemented them – street lamps that were really just candles in glass. And this shorter photoperiod resulted in a very different way of sleeping:

You’d get to bed shortly after darkness had fallen and sleep for several hours. This was “first sleep” (later mistranslated as “beauty sleep”). Sometime around midnight, you’d wake up. You’d putter around, read a little by candlelight (if you were literate and could afford candles, that is!), make love, get up and dance, check on the animals, talk with friends or folks in your tribe, think of stately pleasure-domes in a partial waking dream state… that sort of thing. In short, you would be awake and at least moderately active. You’re not a groggy, grumpy person here, fussing with your pillows, thrashing at the comforter, and agonizing over the alarm clock. You’re reasonably alert and cheery.

Then you’d drift off to “second sleep.” Sounds cool, right, but out of the realm of possibility for us living now? Maybe not.

Studies find that modern humans living in an technological permaglow of light will revert back to the biphasic sleep pattern when exposed to shortened photoperiods (from 16 hours of light to 10 hours of light), so the potential remains.

But very few of us are humans living in contrived study settings, and that’s what could make this one a little tricky. Ideally, biphasic sleep is effortless. It just happens. You wake up, read, talk, use the loo, or do something gentle for a few minutes or a couple hours, and go back to sleep without actively trying to make it happen.

That won’t work for everyone, not without active intervention and formal experimentation. Which brings us to the personal experiment.

But why biphasic sleep?

Mostly because I find the notion that we’re all “doing it wrong” when it comes to a fundamental aspect of our lives – sleeping – extremely interesting. I mean, it’s not like it hasn’t happened to us before (diet and exercise, anyone?). It’s not out of the realm of possibility. I’d even say it’s fairly likely that we’re getting something wrong when we sleep, seeing as how 60% of Americans between the ages of 13-64 report having a sleep problem almost every night, whether it’s waking up feeling groggy or waking up too early. Even those of you who are clued in to the whole Primal thing might find it helpful to explore another way to sleep. In my last post on biphasic sleep, I referred to it as more of a thought experiment than anything else, but today I’m recommending people formally attempt to integrate it into their lives, if only for a month or so.

That said, is there more than one type of biphasic sleeping? Sure:

Natural biphasic sleep

This is what I call normal human biphasic sleep – two four-hour blocks of sleep broken up by an hour or two of wakefulness in the middle of the night. Easy to understand, if hard to implement.

Modified biphasic sleep

This is the kind of biphasic sleep that lifehackers employ. They’re not really interested in anthropological or evolutionary arguments for sleeping a particular way; they want to save time and get the minimum dosage of sleep that confers the maximum amount of benefit. They see sleep as a waste of time, albeit a necessary one. From what I can tell, lifehackers typically sleep for a 4.5 hour block of time – say, from 2 AM to 6:30, which allows them to stay up late, get three, full 90-minute sleep cycles in, and rise early to greet the day. They follow up with a 90-minute nap sometime in the late afternoon, which gives them another 90-minute cycle and enough energy to make it to the next sleep block.

Sidenote: I’m somewhat skeptical of these shortcuts when it comes to sleep. From what I can tell, they focus on REM sleep and seem to classify non-REM sleep as “wasted” sleep, as if it exists only to propel us from one REM session to the next. Eh, I’m not so sure we should be so flippant about messing with a vital physiological process, nor should we immediately discount the importance of “useless” sleep. I have no problem with hacks, usually. In fact, I usually welcome them. Just be careful when hacking something like sleep.

Okay, so how do I do it?

First, you want to determine what kind of biphasic sleep pattern is even possible for you. If you have the freedom to get to bed shortly after dark, wake up in the middle of the night for a couple hours, and go back to bed, go for natural biphasic sleep.

Choose an “absolute latest” morning wakeup time. If you have to be up by 7 AM, that’s going to determine how late you can go to bed.
Determine a bedtime. It should be at least nine hours from bedtime to morning wakeup time, giving you two four hour sleep blocks and one hour of free time in between. If you’re up by 7 AM, you should be in bed by 10 PM. If you want another hour in the middle of the night to do stuff, go to bed by 9 PM.
Reduce exposure to artificial light once the sun goes down, or at least two hours before your scheduled bed time, just like it would have been for most of human history. Turn off the TV, install f.lux on your computer, light some candles, and/or wear blue light-blocking glasses or goggles. It probably won’t work as well otherwise.
If you use lighting during your mid-phase waking period, be sure to wear blue light-blocking goggles or stick to a natural light, like candle or yellow light. Try not to bust out the PS3 for some online gaming.

If you need more alert waking time in a day and would like to try reducing the amount of sleep you require, try modified biphasic sleep.

Choose a 4.5 hour block of time. This will be your “anchor” block of sleep, and most people have success placing this at night or during early morning. Try 10 PM-2:30 AM, perhaps, or 2:00 AM-6:30 AM. Set an alarm, at least until you become entrained to that schedule.
Wake up and go about your day. Get some light exposure, preferably daylight if applicable.
Take a 90 minute nap, to begin 8-10 hours after your wake up time. If you woke up at 6:30 AM, you might nap from 4:30 PM-6 PM.

Set a realistic goal:

“I want to improve my sleep.”
“I want to feel just as refreshed on less sleep.”

Come up with a hypothesis, like:

“Modified biphasic sleep will reduce my sleep requirements while maintaining my wakefulness, productivity, workout recovery, and immune function.”
“Natural biphasic sleep will reduce my nighttime anxiety about waking up and ruining my sleep, thereby improving my sleep.”

Now, we identify some of the variables and think about how they might affect the outcome:

Length of sleep blocks – Are four hours enough during natural biphasic sleep? Do you prefer two three hour blocks instead of a 4.5 hour block and a 90 minute nap?
Timing of sleep blocks – Do you need less time in between the anchor block and the nap? How do you sleep with one hour between your two sleep phases? How about two hours?
Alarm – Does the alarm help or hinder your biphasic sleep?
Light – How does light exposure affect the effectiveness of your biphasic sleep? Is total abstention before bedtime necessary?
Activity while awake – What are you using your free awake time to do? Does reading by candlelight have a different effect on sleep quality when compared to going for a walk?

Next, let’s take some measurements. What to measure?

Productivity – Is your work suffering or improving? How many productive hours are you getting?
General wakefulness – How are your energy levels throughout the day? Are you getting a mid afternoon slump? Use a simple 1-10 scale.
Grogginess – Do you feel well-rested upon waking? After which phase do you feel the most rested? 1-10 scale.
Recovery – How are your workouts? Are your numbers improving or falling?
Immune system – Are you getting sick more often?

Try the biphasic sleep for at least a week, preferably closer to four weeks. Then once you’ve established a baseline and have some data to work with, refer to the list of variables above, make a change to a single variable, and give it another try for some duration to see if biphasic sleep is for you.

This isn’t for everyone. As Robb Wolf points out, when you have 14 hours of uninterrupted darkness and potential sleep time, you have the luxury of being a little more picky with your sleep patterns. When you don’t have emails to answer or an unprecedented renaissance of quality television to tear into, you’re going to get sleepy when darkness falls, go to bed pretty early, wake up after several hours, do your thing, and go back to sleep for another several hours. Biphasic sleep is probably natural. But we’re not living in very natural times. Or, if we are, natural means something different from what it once did. That’s the whole premise of the Primal Blueprint, after all – identifying what our ancient genes expect from the environment and figuring out how to modify our modern environment to fit those genes.

Let me know what you think in the comment board, and be sure to check out today’s contest.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending more than three decades educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.