This article makes me want to get a DNA test. In my family, it’s very common to sleep in the six-hour range. I personally sleep from 10 pm to 4:25 am every day, often waking up around 4:15 am before my watch vibrates to wake me.
If I sleep eight hours, I feel groggy, jet-lagged, and generally have a day where I’m slogging through molasses to get from one task to the next.
My wife has raised concerns about my sleep pattern, so I started using sleep-tracking tools like Fitbit and, more recently, an Apple Watch. She tracks her sleep too, and the big difference we’ve noticed is that I fall asleep within about two minutes, and my “sleep efficiency” using these tools is 98%. If I’m traveling and feel a bit jet-lagged, I can take a 20-minute nap (often without an alarm) and wake up feeling refreshed. She also seems to wake up a lot, most nights I "sleep like a log" and I only wakeup in the morning.
My mother has the same pattern but stays up later and sleeps about six hours into the morning. I used to do this too, but around age 23, I switched to an earlier bedtime and a consistent daily routine. When I became a “morning person,” I found I could code like crazy in the morning before “starting” my day, and this rewarding experience reinforced the habit.
I’ve tested this pattern in many ways, including not using an alarm (I still wake up around the same time for weeks at a time) and using a “light clock” I built with a Raspberry Pi to slowly brighten the room. Again, I wake up after roughly 6 hours and 20 minutes. Now, I use my Apple Watch to vibrate as a gentle reminder to start the day. On weekends, I keep the same schedule and use the extra time to read or hack away at side projects, often coding until the late afternoon when my wife protests enough that I need to stop and hang out or do my honey-do's.
About 10 years ago, during my annual checkup, my wife asked my doctor about this sleep pattern. The doctor asked me several questions, seemingly looking for signs of sleep deficit or dysfunction. In the end, he said I could do a sleep study but concluded, “If it works, don’t break it.”
As for productivity, I’ve found I can code effectively from 4:30 am to 8:30 am, then shower and work from 9 am to 6 pm without much trouble. I also practice intermittent fasting, typically eating only at 6 pm, with a protein shake around noon. This habit happened by accident—I realized breakfast slowed me down, and eating lots of carbs impaired my cognitive function and ability to code or handle complex tasks in the morning.
Before you ask, I generally don’t use caffeine or other stimulants. Occasionally, I’ll have one cup of coffee around 9 am as a social habit, but I recently stopped that again and actually feel better. I’ll most likely drop it again for a while until it sneaks back in again.