Reading a book before bed can improve sleep quality but it depends on what you read it on: A 2014 study found people using a light-emitting device took nearly 10 minutes longer to fall asleep than with a printed book

If you reach for a book before bed, you may be doing your sleep a favor. But there is a catch: research suggests the benefits of bedtime reading may depend on whether you are turning pages in a printed book or reading them from a glowing screen.

A 2021 randomized trial published in the scientific journal Trials found that reading a book in bed before going to sleep improved sleep quality compared with not reading in bed. The online “People’s Trial” involved 991 people, who were randomly assigned to either read a book in bed for seven days or avoid reading in bed.

Among participants who provided sleep data, 42% of those who read in bed reported improved sleep, compared with 28% in the group that did not read. The researchers estimated that sleep improved for between 8% and 22% more people in the reading group, supporting the idea that a bedtime book could be a useful part of a sleep routine.


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But there is an important catch if your idea of a bedtime book involves an iPad or another light-emitting screen.

A 2014 study by researchers from Penn State, Brigham and Women’s Hospital and Harvard Medical School compared people reading an iPad with people reading a printed book before bed. The study involved just 12 adults, who spent two weeks in a controlled setting and read from an iPad for five nights and a printed book for another five nights.

The researchers found that participants reading from the light-emitting iPad took nearly 10 minutes longer to fall asleep than when they read a printed book. They also reported being more tired and taking longer to become fully alert the following morning.

The researchers linked the difference to the light emitted by electronic devices. Evening exposure to light can suppress melatonin, a hormone involved in regulating sleep, while short-wavelength-rich blue light from screens can have a stronger effect on the body's sleep and circadian rhythms.

So, the two studies point to a useful distinction: reading itself may be beneficial for sleep, but reading on a bright, light-emitting screen may work against some of those benefits.

In simple terms, if you want to make reading part of your bedtime routine, the old-fashioned paper book may have an advantage over a glowing screen.