Sometimes I wake up early in the morning, and manage to roll over and go back to sleep. However, I find that the less time I have to catch those extra z’s, sometimes it leaves me feeling more tired than if I had just got up when I woke.
On the times that I just get up, sometimes I feel really tired and sometimes quite rested, despite the length of my sleep. On extended analysis, using data from both my watch (fairly accurate) and my CPAP (very accurate) it is clear that the real determining factor is not length of sleep, but amount of *deep* sleep. By *deep* sleep, I actually mean deep sleep *and* REM sleep, as my devices cannot differentiate between them.
This morning is a good example. I woke at 6am – knowing that I went to bed at 11pm, and read for at least 30 minutes, made me aware that I was well under the 7-8 hours I am aiming for. However, I felt wide awake.
Checking my sleep chart, I see that of that 6.5 hours sleep, 5 of it was deep undisturbed sleep. On another night, it could be as little as 3. That is what makes the difference.
This may all seem fairly obvious, but it is worth remembering. Increasing the quality of your sleep – by good sleep hygiene; reducing distractions like power lights on clocks and devices (either by configuration, where available, or black insulation tape!); restricting the use of light-emitting electronic devices before sleep (plain e-books are ok); these all help maintain a deep sleep.
If you have external light shining into your bedroom (street light, or garden floods from neighbours), don’t think “oh, I can still sleep, despite that” – block the light out, with curtains or blinds; as it will affect the quality of your sleep. If you can sleep with a eye-mask, that can also be effective (I can’t, but I know people who can).
Finding ways to measure the quality of your sleep can also help. As mentioned above, I use both a smart-watch and a CPAP, but there are also Android and iOS apps that let you use your phone as a sleep monitor.