Hey, sleep lovers! Ever find yourself wide awake at two or three AM, wondering why your brain’s ready to party? That’s been me most nights, and it might be your body tapping into something called biphasic sleep. Let’s unpack what it is, why it happens, and how you can experiment with it to see what’s best for your brain.

What’s Biphasic Sleep Anyway?

It’s when you split your sleep into two chunks, often with a little awake time in between. Think: a few hours of sleep, waking up around two AM to chill—maybe read, snack, or just think—then diving back into a “second sleep.” Crazy, right? But before the Industrial Revolution, this was super common. Old diaries and medical texts show folks in Europe and beyond treated that midnight wake-up as no big deal—time for chores, chats, or even prayer. Then came factories and electric lights, pushing us toward the one-shot, eight-hour monophasic sleep we know today. But is that solid block really the best?

Is Biphasic More Natural?

Biphasic sleep might sync better with our natural rhythms. Historian Roger Ekirch’s research shows it popped up across cultures before artificial light threw our circadian clocks out of whack. Even now, some hunter-gatherer groups like the Hadza in Tanzania mix nighttime rest with daytime naps, totaling six to seven hours. It suggests our brains might dig that split-sleep vibe.

Brain Benefits of Biphasic Sleep

But is it better for your brain? Possibly…

That wakeful period could help your brain “defrag,” sorting memories and emotions. A 2011 study in the Journal of Sleep Research found biphasic sleep boosts REM—the dreamy stage tied to creativity and memory. I’ve noticed this myself; my biphasic nights come with more vivid dreams, due to more REM, according to my Oura ring sleep tracker. Siesta cultures, like in Spain, also show naps can lower stress and sharpen focus by cutting cortisol, per studies. Monophasic sleep is solid, too, if you hit enough deep and REM stages, but biphasic might shine if age or schedule make a full night’s sleep tough.

Why the Midnight Wake-Up?

Speaking of age, older folks often slide into biphasic naturally—National Sleep Foundation data says people over sixty wake at night and nap more, thanks to lower melatonin. Now, why that two or three AM wake-up? It could be histamine from foods like aged cheese or fermented stuff, which keeps you alert hours after eating, per the Journal of Clinical Sleep Medicine. Cortisol spikes from stress or blood sugar dips from late meals might also jolt you awake, according to Sleep Medicine and Journal of Clinical Endocrinology studies. For me, those early wake-ups feel like my body’s rhythm, and it gives me time to pray and read my Bible without distractions or interruptions.

Since by face sleep was the norm for the vast majority of human existence, I’m inclined to think that would be the better way, since we haven’t had much time to adapt since the industrial revolution began, especially in the context of how long we’ve been on the planet, but if you are already doing monophasic sleep, and that’s going well for you, that’s probably your natural circadian rhythm and you should probably stick with it. Some people did best with monophasic sleep before the industrial revolution, so don’t let this post make you think that is a bad idea. If it’s working for you, don’t mess with it! This post is mainly for people who sleep biphasic, or start to do that more as they age, so they don’t stress about it being unhealthy.

How About Some Sleep Experiments?

Here’s where it gets fun: you can test biphasic and monophasic sleep to see what your brain prefers.

• Biphasic Experiment: Aim for five to six hours of sleep at night, let yourself wake naturally (even at two or three AM), stay up for thirty to sixty minutes doing something calm—like reading (paper only – no screens) or journaling (paper again), then sleep more, seeing how long that phase lasts. Or, add a twenty-to-thirty-minute afternoon nap to a shorter night. Track your energy, focus, and mood for a week in a notebook. Tracking and recording is vital to know which works best for you.
• Monophasic Experiment: Aim for a consistent seven to eight hours at night, hitting the sack and waking at the same time daily. Keep screens off an hour before bed to boost melatonin. Cut down on histamine foods, especially from noon on. Be sure to journal this experiment too. If you can use a sleep tracker for both experiments, that’s the ideal scenario, but journaling by itself can be enough if you don’t already have a good sleep tracker.

Compare notes: Do you feel sharper with biphasic’s extra REM? Or does monophasic’s simplicity keep you energized? Give it a go! Your brain might love the split-sleep rhythm, or maybe you’ll find monophasic is your jam.

References:

• https://www.sleepresearchsociety.org/
  (Home of the Journal of Sleep Research, where the 2011 study on biphasic sleep and REM can be searched for)
• https://www.sleepfoundation.org/
  (National Sleep Foundation’s site for data on aging and sleep patterns)
• https://jcsmonline.org/
  (Journal of Clinical Sleep Medicine, for studies on histamine and sleep disruption)
• https://www.sleepjournal.org/
  (Sleep Medicine journal, for research on cortisol and nighttime wake-ups)
• https://academic.oup.com/jcem
  (Journal of Clinical Endocrinology, for studies on blood sugar and sleep)
• https://www.roger-ekirch.com/
  (Historian Roger Ekirch’s site, for his research on biphasic sleep history)