Children with access to "small screen" devices - such as tablets or smartphones - in their bedrooms get less sleep at night, according to a new survey.

Researchers looked at the sleep patterns of 2,000 middle school kids who had electronic devices in their bedrooms. The kids were all enrolled in the Massachusetts Childhood Obesity Research Demonstration Study from 2012 to 2013, reported AFP. 

Those with "small screen" devices in their bedrooms received 21 fewer minutes of sleep per night than children whose rooms were free of such technology. They were also more likely to admit to feeling sleep deprived, reported AFP.

The small screens beat out kids with TV access at night. Of the middle schoolers surveyed, those with TVs in their bedrooms had 18 minutes less sleep than those who did not.

"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." 

"Small-screened" devices aren't only affecting children. A separate study published in December found that adults who read on a tablet or e-reader just before bed slept worse at night than those who didn't. 

The study on the "small screens" preventing children from sleeping at night was published in the January 5 edition of the journal Pediatrics.