Here's a bit of self-serving science: According to a study in Sleep Medicine released earlier this year (but just discovered by me), a night of disrupted sleep can be just as bad as a night of barely any sleep at all when it comes to mood and brain function.
For the last couple of weeks, I have woken up at 3:00 or 3:30a.m. and had a very difficult time getting back to sleep. The result has been irritability, increased anxiety and a harder time focusing during the day. It started with my cat (who is surprised by this?) who chose this pre-dawn time to knock things off my bedside table to get my attention several days in a row.
But even after I banished the cat from the bedroom, I still find myself waking up at 3:00 or 3:30, falling back to sleep for a little while and waking back up a few times before the alarm goes off. I'm in the middle of marathon training and my work day usually lasts 8-9 hours, so this is not a fun situation.
The Sleep Medicine study won't help me sleep better, of course, but it validates my assumption and concern that even though I have technically been asleep for seven or eight hours each night, the fact that I'm punctuating that sleep with periods of waking is doing a number on my mind and body. It appears to be one of the first studies to focus on the impact of interrupted sleep on the emotions, as opposed to just on physical well-being, and one of the first to study sleep issues in an at-home setting.
The study had 61 healthy adults self-report their mood after a normal night of sleep and after a night of either four hours or less in bed or a night of induced night-wakings across eight hours in bed. Sleep was both self-reported with sleep diaries and through the use of actigraphy, which is usually done with a watch-like machine worn by the subject.
According to the results, both induced night-wakings and sleep restriction resulted in increased depression, fatigue and confusion during the day, as well as "reduced vigor." And there was no major difference whether you were only asleep for a few hours or had a long, uninterrupted night in bed.
Now my question is this: how to break out of a sleep schedule that includes interruptions? I have found a few suggestions from various sources, one of the biggest ones being "don't look at the clock/phone when you wake up." That is definitely something I need to work on...!