It is not how long but quality of sleep that determines sleep perception

People with insomnia wake up more often during the night, making them feel that they sleep worse. This is the conclusion of PhD student Lieke Hermans. In her dissertation she investigated the sleep quality in people with insomnia. In the future her results will offer a better understanding about the causes of poor sleep quality. Hermans also hopes her research will make patients feel that they are being taken more seriously, because there will be a better explanation for their sleep complaints. Lieke Hermans defends her thesis at the Department of Electrical Engineering at Eindhoven University of Technology on 11 December.

Around 1 in 10 adults suffers from insomnia, or chronic sleeplessness. They are very unsatisfied about their sleeping pattern and experience complaints such as fatigue, concentration problems and mood disorders. This has a major impact on their daily lives. However, when the sleep of people with insomnia is measured in a sleep laboratory, the complaints cannot always be fully explained by the measured amount of sleep. Many of them think they lie awake for a long time, while measurements show that they fell asleep relatively quickly.

Such findings lead scientists to believe that not only the quantity of sleep is important, but also the quality of sleep. It is possible that poor sleep quality causes people with insomnia to feel that they sleep very little, when in fact they do not. Sleep quality is still a relatively unknown phenomenon in science. PhD student Lieke Hermans wanted to learn more about this.

First hour of sleep at night is key

In her dissertation she therefore studied people with insomnia, and looked at the connection between waking up during the night and the measured sleep quality. Hermans: “Brief awakenings at the beginning of the night appear to have an important influence on the feeling of falling asleep, especially in people with insomnia.”

Hermans then developed an index that can express an individual’s sensitivity to sleep fragmentation, or short portions of sleep. The so-called sleep fragment perception index (SFPI) can be used to better analyze the causes of insomnia. Hermans: “We compared the index of healthy sleepers and people with insomnia. The latter group turned out to need longer periods of sleep to experience that they are indeed asleep. People with insomnia who wake up within half an hour after falling asleep, may feel that they have not slept at all, while good sleepers only need 10 minutes of continuous sleep to be aware of their sleep.”

The effect of sleep medication on the feeling of falling asleep can also be investigated with this index. Moreover, Hermans developed a method to compare the fragmentation of sleep throughout the night. In this way she could see how often people wake up from different types of sleep. Hermans: “People with insomnia generally woke up more often than healthy sleepers, especially during Non-REM sleep, the non-dream or ‘normal’ sleep.”

PhD thesis: Sleep structure & sleep perception in insomnia. Supervisors: Sebastiaan Overeem, Merel van Gilst and T.R.M. Leufkens. This research is part of the Eindhoven MedTech Innovation Center (e/MTIC), a collaboration between the Catharina Hospital, the Maxima Medical Center, the Center for Epilepsy and Sleep Problems Kempenhaeghe, Philips and TU/e.

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