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Nightly use of eReaders may alter circadian clock

The use of electronic devices such as eReaders before bedtime can worsen sleep deficiency, according to a recently published study.

“Electronic devices emit light that is short-wavelength-enriched light, which has a higher concentration of blue light — with a peak around 450 nm — than natural light,” Anne-Marie Chang, PhD, assistant professor of biobehavioral health at Penn State University, said in a press release. “This is different from natural light in composition, having a greater impact on sleep and circadian rhythms.”

The researchers examined 12 healthy young adults in a 14-day inpatient randomized study to assess patients’ who read from a light-emitting eBook in a very dim room for approximately 4 hours before bedtime for 5 consecutive evenings. They also studied patients who read from a printed book in the same dim room for approximately 4 hours before bedtime for 5 consecutive evenings.

The investigators found that the light-emitting eBook suppressed evening levels of melatonin by 55.12% vs. no suppression in the print book assessment (–18.77%), based on findings from the fifth night (P<.001).

Those who read light-emitting eBooks also averaged nearly 10 minutes longer time to fall asleep vs. those who read print books (P=.009), according to data.

The patients also demonstrated less rapid eye movement sleep following the light-emitting eBook reading vs. print books (P=.03), according to data.

“We live in a sleep-restricted society, in general,” Chang said. “It is important to further study the effects of using light-emitting devices, especially before bed, as they may have longer term health consequences than we previously considered.”

Disclosure: See the study for a full list of relevant financial disclosures.