A study published in the journal Sleep finds that many teens are using their cellphones for middle-of-the-night chats, and many of them are paying the price with fatigue.

The study, authored by Jan Van den Bulck, PhD, of the Leuven School for Mass Communication Research at Katholieke Universiteit Leuven in Belgium, focused on 1,656 school children with an average age of 13.7 years in the youngest group and 16.9 years in the oldest group.

They found that 62 per cent of them admitted to using their cellphones after bedtime.

Those using cell phones less than once a month increased the odds of being very tired one year later by 1.8. Those who used it less than once a week were 2.2 times more likely to be very tired. Using it about once a week increased the odds by 3.3, and those who used it more than once a week were 5.1 times more likely to be very tired.

Dr. Van den Bulck noted that parents often worry about their children watching too much TV or what they're doing when they're surfing the Internet, while the cellphone is seen only as a simple communication device.

"This study shows that parents should be aware of the fact that young people today use the modern means of communication in ways they probably cannot imagine," he says.

"Taking a mobile phone to your bedroom is not trivial. [Young people] spend a lot of time 'connecting' to other people, and some of them do this all hours of the night," he says.

The American Academy of Sleep Medicine (AASM) offers for adolescents the following tips on getting a good night's sleep:

• Keep computers and TVs out of the bedroom.
• Follow a consistent bedtime routine. Get a full night's sleep every night and get up at the same time every morning.
• Establish a relaxing setting at bedtime. Make your bedroom quiet, dark and a little bit cool.
• Avoid foods or drinks that contain caffeine, as well as any medicine that has a stimulant, prior to bedtime.
• If after-school activities are proving to be too time-consuming, consider cutting back on these activities.
• Do not go to bed hungry, but don't eat a big meal before bedtime either.
• Avoid any rigorous exercise within six hours of your bedtime.
• Experts recommend that adolescents get about 8-9 hours of sleep each night for good health and optimum performance.
• Parents who suspect that their teen might be suffering from a sleep disorder are encouraged to consult with their teen's pediatrician or a sleep specialist.