Using smartphone before bedtime could lead to poorer quality sleep

People who spend more time staring at their phones before bedtime get a worse night’s sleep, researchers found, in the first study that directly measures screen time using a mobile application.

Previous studies have found an association between using devices with screens and poor sleep quality. However, scientists aren’t sure exactly why that is. Exposure to blue-colored light, such as that produced by electronic screens, is known to stimulate wakefulness. Electronic device use before bedtime might also simply stress us out. And some research has shown that there are associations between simply having electronic devices in the bedroom and worse sleep — possibly pointing toward some other confounding factor.

Dr. Gregory Marcus, cardiologist at the University of California, San Francisco, used data from the Health eHeart Study, which was set up to do research on cardiovascular disease. Participants in the study recorded many different things about themselves, including when they went to bed, how long they slept, and how well they slept, but didn’t know when reporting the data that it might be examined for a relationship with cellphone use.

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