Researchers out of Lausanne University Hospital have found new insights into what constitutes deep sleep, challenging the traditional belief that slow brain waves translate into the feeling of deep sleep.
The researchers look at a group of consumers who suffer from insomnia.
Researchers looked 10 people with insomnia and 20 people who generally sleep normally to undergo EEG recordings as they slept in a lab.
The finding show that the 'normal sleepers' reported experiencing their lightest sleep during the first two hours of sleep, a period of non-REM sleep.
However, the insomniacs, reported feeling more awake than those who slept normally those first two hours. The insomniacs also reported feeling like they slept more lightly during REM sleep, which prior research has suggested is the time when people normally sleep the deepest.
One important piece to note, the insomniacs were often sleeping during times that they thought they were awake, suggesting they get more sleep than they think they do. But the researchers also found that there was a certain degree of overlap between slow wave sleep and fast-wave sleep in the insomniacs—an indication that they are both awake and asleep at the same time.
This finding challenges the belief that slow waves necessarily indicate both heavy sleep and the feeling of having slept heavily afterward.