Should you read before going to sleep? The short answer is yes: reading is one of the best transitions to sleep we know of, with one caveat, and it concerns the format. Reading is not the problem in the evening; the light from certain screens is, and above all what else we do with them.
This article sticks to established facts: why reading helps you switch off, what the landmark study on evening screen reading actually shows, and how to organise your bedtime reading so it serves your sleep instead of delaying it.
Why reading helps you fall asleep
Sleep cannot be switched on at will: it comes when physiological and mental activation winds down. Yet many people get into bed with a brain still hard at work: emails, to-do lists, rumination. Reading acts here as a decompression chamber: it occupies your attention with content unrelated to your worries, letting activation subside on its own.
It also works as a routine signal. Classic sleep hygiene advice insists on repeating the same sequence of calm actions every evening: over time, the brain associates that sequence with falling asleep. A chapter read under the same conditions every night becomes a ritual telling the body the day is over.
Let us be honest: studies that directly measure the effect of reading on sleep quality remain scarce, and the spectacular figures circulating online often come from fragile sources. What happens when you read on a bright screen in the evening, however, has been measured very rigorously.
The landmark study: Chang et al., PNAS, 2015
In 2015, a team from Brigham and Women's Hospital and Harvard, led by researcher Anne-Marie Chang, published in the journal PNAS the experiment that became the reference on this topic. Twelve participants spent two weeks in a laboratory under strictly controlled light conditions. In the hours before bedtime, they read either a paper book under dim light or the same kind of content on a backlit tablet set to maximum brightness, five evenings in a row in each condition.
The results are clear. After the tablet reading evenings, the secretion of melatonin, the hormone that prepares the body for sleep, was delayed and reduced compared with the paper reading evenings. Participants took longer to fall asleep, felt less sleepy at bedtime and reported being less alert the next morning. Their biological clock was shifted to a later time.
The study should also be read with its limits in mind: twelve people, about four hours of reading per evening on a tablet pushed to maximum brightness, laboratory conditions far removed from a real twenty-minute read in night mode. The study does not say that screen reading destroys sleep; it demonstrates that light emitted by a screen in the evening acts on the biological clock, which matches what circadian science has established elsewhere about evening light exposure.
Paper, e-reader, phone: which format to choose in the evening
| Format | Light | Distraction risk | Evening verdict |
|---|---|---|---|
| Paper book, dim lamp | Reflected, low | Almost none | The safest choice |
| E-ink e-reader, low front light | Low, directed at the page | Very low | Very good compromise |
| Tablet or phone at full brightness | Emitted, direct | High | Avoid at bedtime |
| Phone in night mode, minimum brightness | Emitted, reduced | High | Acceptable with discipline |
The e-reader deserves a clarification: unlike a tablet, its so-called front light projects a weak light onto the page, not directly into your eyes. Set to minimum and to a warm tone, it comes close to paper book conditions. Digital reading is not the problem in itself; the problem is the amount of light received and the time at which you receive it.
If your phone is your only reading device, two settings are essential: night mode, which warms the screen colours, and brightness at minimum, ideally with a dark theme. But the real danger of the phone in bed is not its light.
The real sleep thief: scrolling, not reading
A chapter has an ending; a news feed does not. The risk with a phone in bed is the switch: you close your reading app, open a social network for 'just two minutes', and content designed to hold your attention does the rest. Reading is an activity that stops by itself; scrolling is an activity designed not to stop. We covered this imbalance, figures included, in our article on screen time versus reading https://www.cobaltapp.io/fr/blog/temps-ecran-contre-lecture-chiffres
A final word on a figure you will see everywhere: reading supposedly reduces stress by 68 percent in six minutes, according to a study attributed to the University of Sussex. That work, commissioned by a commercial player and never published in a scientific journal, should be quoted with great caution. We tell its story, and what solid research says about reading and stress, in our dedicated article https://www.cobaltapp.io/fr/blog/meilleurs-livres-stress-anxiete
An evening reading routine that holds up
Concretely, here is what sleep hygiene advice applied to reading boils down to: a fixed time, around 20 to 30 minutes of reading, warm and low light, and a book chosen for pleasure rather than performance. A gripping but not distressing novel, an essay that nourishes without demanding note-taking: the goal is to switch off, not to learn at all costs.
And if your mind is still racing too fast for a full chapter, start shorter: a few pages are enough to create the signal. What matters is not how much you read, it is the regularity of the ritual.
At Cobalt, we are well placed to say it: a reading app is still a screen. That is why our book summaries, designed for 15-minute sessions, fit best during the day: a lunch break, a commute, a quiet moment. In the evening they serve differently: spotting in a quarter of an hour the book that is truly worth it, then picking up paper or the e-reader at bedtime. Our summaries are freely available here https://www.cobaltapp.io/fr/resumes and the app can be downloaded here https://www.cobaltapp.io/download