We all know staring at a glowing screen in bed is a bad idea - but it turns out adults are nearly as bad as teenagers at doing it anyway.

A new study has found 42 per cent of adult Australians continue looking at their devices after lights out, resulting in poor sleep, going to sleep later and less sleep overall.

While the impacts on sleep weren't shocking to the researchers, study lead Dr Michele Lastella said he was surprised at how many adults continue looking at screens in the dark despite knowing it was bad for their health.

"It's really well known now that this blue light emitted from those devices is not good for sleep, but people still do it. It's like fatty foods - we know they're not good for us but we still eat them," he said.


The researcher called for more work to better understand why adults feel the need to reach for their devices late at night.

"The scary thing is that these devices are becoming more and more prominent, we're able to use them to access social media, emails, work through them so it's not going away."

Lastella admitted he partly carried out the survey to win an ongoing argument he's had with his wife about good sleep hygiene.

"This is one of the reasons I'm doing the research - to prove to her that it's not good for you."

The researchers from Central Queensland University surveyed 1210 adult Australians with an average age of 54. Of those, 504 admitted using their phone or tablet after turning the lights out.

There was a clear downward trend as people got older, but Lastella suspected that may change as those who have grown up with smartphones age. "It might be that in 30 years' time those people are still using their phones at a relatively high level."

Lastella said it was concerning to see adults had embraced the trend almost to the same extent as teenagers - one study found 62 per cent of teens use their phones after dark.

Most studies till now have focused on children and adolescents, but news that adults are also losing sleep over technology is no great surprise, New Zealand sleep physician Dr Michael Hlavac told the Herald.

"Adults tend to adopt the same use of devices at night, although maybe for different reasons," said Hlavac, who runs a sleep disorder clinic.


"My patients, anecdotally, are on their phone and tablets looking at Netflix, reading the news, not using as much social media as their younger counterparts ... but the implications are the same. There is a significant effect on sleep duration and sleep quality."

The physician said he was stunned by how many respondents continued to look at glowing screens in bed.

"This suggests there is a vast number of people who will never cross my threshold but have similar problems [to my patients]. It has implications well beyond medicine - for the workplace, for productivity, for driving safety. This is far-reaching."

The research found any use of electronic devices after lights out was associated with poor sleep quality - suggesting even a quick scroll through emails or glance at the day's news could have long-lasting repercussions.

That could be because melatonin - the hormone that tells us we're getting drowsy when it gets dark - is extremely sensitive to light, Hlavac said.

"If you shine a light in someone's eyes, their melatonin levels will drop. So even a little light exposure in theory will very rapidly have an effect."

Lastella's research will be presented at Sleep DownUnder 2017, the annual conference of the Australasian Sleep Association, held from October 26-28 at the SkyCity Auckland Convention Centre, New Zealand.