The findings in the January 5 edition of the journal Pediatrics show that having a so-called "small screen" within reach was slightly worse than a television set when it came to sleep deprivation in a group of 2,000 middle school kids.
Overall, those with access to smartphones and tablets got nearly 21 fewer minutes of sleep per night than children whose rooms were free of such technology, and they were more likely to say they felt sleep deprived.
"Presence of a small screen, but not a TV, in the sleep environment, and screen time were associated with perceived insufficient rest or sleep," said the study led by Jennifer Falbe of the University of California, Berkeley School of Public Health.
"These findings caution against unrestricted screen access in children's bedrooms."
Participants in the study included 2,048 fourth- and seventh-graders enrolled in the Massachusetts Childhood Obesity Research Demonstration Study from 2012 to 2013.