For most of the last fifteen years, I’ve averaged about six, maybe six and a half hours of sleep a night.  And, honestly, that always seemed like enough.  I woke up before my alarm clock, and felt like I was functioning totally fine.

With each year, I read more and more research about the negative impact of insufficient sleep, the countless adverse consequences that slowly accrue if you don’t hold to seven and a half or eight hours nightly.  But, as I said, I felt okay, so I tended to shrug all that research off.

Then, eventually, I came across a study on the cognitive effects – as well as the perceived cognitive effects – of lack of sleep.  The researchers started out by getting a group of people caught up on sleep/well rested.  Then, for one night, they had the subjects cut back, sleeping six hours rather than eight, and assessed them with a battery of cognitive tests the following day.  Further, they then asked the subjects how they thought they had done on the tests.

After that first night of short sleep, the people reported feeling tired, and assumed they had performed worse on the tests than when they were sharp and rested.  And, indeed, they were correct.

Then, a second night in a row, they slept for just six hours.  Once again, they thought their scores had further declined, and once again, they were right.

Third night, third day, same thing.

But then, the fourth day!  For yet another night, the people slept six hours, and for yet another day, they took a battery of tests.  Except, this time, the people felt totally fine.  As they explained to the researchers, they had finally adjusted to the shorter nights of sleep.  They were back to feeling good, and they knew their scores were back up, too.

Problem was, they were completely wrong.  Just as before, their scores continued to decline with each day of sleep deprivation.  But after the fourth day or so, they simply lost the ability to recognize as much any longer.

That study definitely gave me pause, made me question my own self-assessment of how well I was functioning on my standard six hours and change.  Enough so that, despite a decade and a half of habit to the contrary, I decided it was worth some self-experimentation.  I made some serious lifestyle shifts, and started sleeping a full seven and a half or eight hours every single night.

And, actually, for the most part, I felt pretty much exactly the same as I did before.  But then, every so often, I ended up once again short-sleeping, and I felt terrible enough to realize the necessity of the shift.

I was thinking about that today, because for the past two nights I stayed up way past my bedtime, unable to put down a good book.  And while I don’t really regret that (in the words of Lincoln, “it’s been my experience that those with no vices have very few virtues”), I now definitely feel the effects of those two six-ish hour nights.  I’m sluggish, foggy, cranky, craving sweets, and ready for a nap.  In short, I feel like crap.

And, at the same time, I don’t mind at all.  As ever, it’s a good reminder that those extra hours snoozing aren’t wasted.  Despite years of convincing myself to the contrary, I really do need seven and a half or eight hours of sleep to be at my best.

With that, I’m off to bed.