Can sleeping with a smartphone disturb sleep? Try to answer this question in the How Smart Is It to Go to Bed with the Phone? The Impact of Short-Wavelength Light and Affective States on Sleep and Circadian Rhythms, published on the Clocks & sleep.
The researchers explain: "Previously, we presented our preliminary results investigating the effects of short-wavelength light from a smartphone during the evening on sleep and circadian rhythms. Here, we now demonstrate our full sample, where polysomnography and body temperature were recorded during three experimental nights and subjects read for 90 min on a smartphone with or without a filter or from a book.
Cortisol, melatonin and affectivity were assessed before and after sleep."
Can sleeping with a smartphone disturb sleep?
Researchers then added: "This study investigated the impact of evening short-wavelength light on sleep and circadian rhythmicity.
We assessed light-induced changes due to evening smartphone use in comparison to reading a book under dim light conditions. Additionally, we investigated whether a blue-light filter is able to attenuate light-induced effects.
Furthermore, the impact of positive and negative affective states in the evening on subjective and objective sleep quality was assessed. The results provide evidence that short-wavelength light can affect objective sleep as well as circadian parameters.
These results confirm our earlier findings, indicating reduced slow-wave-sleep and -activity in the first night quarter after reading on the smartphone without a filter. The same was true for the cortisol-awakening-response.
Although subjective sleepiness was not affected, the evening melatonin increase was attenuated in both smartphone conditions. Accordingly, the distal-proximal skin temperature gradient increased less after short-wavelength light exposure than after reading a book.
Interestingly, we could unravel within this full dataset that higher positive affectivity in the evening predicted better subjective but not objective sleep quality. Our results show disruptive consequences of short-wavelength light for sleep and circadian rhythmicity with a partially attenuating effect of blue-light filters.
Furthermore, affective states influence subjective sleep quality and should be considered, whenever investigating sleep and circadian rhythms. The study was carried out over the course of more than a year and therefore during different seasons.
Therefore, it might lack comparability to data, which were recorded only during one season, as results were not controlled for individuals’ light exposure prior to laboratory nights. However, light exposure, especially in the morning, is also capable of influencing the circadian rhythm."