When talking about the topics sleep efficiency and sleep debt, of course the waking hours have to be considered as well. In case of suffering under falling asleep- and/or sleep-through-disturbances or “waking up to early”, you need to consider this, too. Of course, a measuring of the sleep is helpful here. Or you will need to find your waking hours by yourself – and this is difficult, most of the times.
In the end, the sleep efficiency is a decisive factor for your sleeping quality: the physiologically actually necessary sleep demand of a human being depends on different factors like genes, age, sleeping routine, health and inner clock. Besides the sleeping duration the course of the sleeping phases is decisive: beginning with the phase of falling asleep, the phases of light sleep up to the very important deep sleep and REM-phases. Such a sleeping cycle lasts about 90 to 100 minutes, an efficient sleeper is going through these phases five times – ideally without any big interruptions. Out of it, you can calculate a sleeping duration of 7.5 to 8.0 hours, on an average.
The last two decades we have lost about two hours of night-sleep, which means, that we clearly have slept longer in earlier days – or maybe just have spent more time in bed.
Nowadays, besides sleep duration especially sleeping quality and sleeping efficiency are crucial. Sleeping efficiency means the actual sleeping duration, the time one is really sleeping, in reference to the time one was spending in bed for sleeping. When someone is in bed for ten hours and only sleeping seven hours, sleeping efficiency is 70 per cent. A very good sleeper has an efficiency of 98 per cent and good sleepers far more than 90 per cent. Below 85 per cent is an indication for falling-asleep- or sleep-through disturbances.