Late-Night Teen Cell Phone Use a Threat to Sleep

LEUVEN, Belgium, Sept. 4 -- Just because adolescents go to bed, that doesn't mean they stop calling and texting their friends, and that may leave them bleary-eyed in the morning, researchers here reported.

Adolescents who use their mobile phones for calling friends and sending and receiving text messages after bedtime awaken sleep-deprived and tired, Jan Van den Bulck, Ph.D., of Katholieke Universiteit Leuven here, reported in the Sept. 1 issue of Sleep.

Heavy use of TV, internet, and computer games in the bedroom has been linked to reduced time in bed and to sleep disturbances, although adolescents often claim they need these media as "sleep aids."

Much of the teen use of cell phones involves the simple pleasure of being permanently connected, day and night, to a group of friends, Dr. Van den Bulck said. However, he added, little has been known about the impact of cell phone use on sleep.

To assess the prevalence of night-time mobile phone use and its relationship to tiredness with a one-year follow-up, Dr. Van den Bulck studied 1,656 second-year and fifth-year secondary school children in 15 schools in Flanders.

Baseline data were collected in February 2003 with a follow-up in 2004 and another in 2005.

Of the children (52.1% boys), the average age was 13.7 years in the youngest group and 16.9 years in the oldest group at baseline. Tiredness was self-reported.

Only 38% of the participants never used their mobile phone after lights out. Overall 35% of the cases of being very tired were attributed to the use of the mobile phone.

Multinomial logistic regression showed that after a year:

• Using the mobile phone less often than once a month increased the odds of being very tired by 1.8 (95% CI 1.2 - 2.8);
• Using the phone less than once a week more than doubled the tiredness odds (OR 2.2, 95% CI 1.4 - 3.5);
• Using it about once a week tripled the odds (OR 3.3, CI 1.9 - 5.7);
• Using it several times a week yielded a five-fold increase in the odds of being very tired (OR 5.1, CI 2.5 - 10.4).

Time of calling, ranging from right after bedtime to any time of the night, also made a difference in the one-year tiredness measure. In most cases calling happened right after lights out. Yet a considerable amount occurred before 3 AM, and about a fifth of the adolescents reported that sending or calling could happen at any time of night.

Use of the phone right after lights out increased the odds of being very tired by 2.2 (CI 1.4 - 3.4); between lights out and 3 AM, the odds were 3.9 times higher (CI 2.1 - 7.1), and for those who used it at any time of the night the odds were 3.3 times higher (CI 1.8 - 6.0).

Among the study's limitations was the use of self-reports. Usually giving socially desirable replies, a potential source of bias in such studies, would not seem to have occurred here, as it is unlikely that students believe that underestimating this behavior is socially desirable.

It is also customary to warn readers about drawing causal conclusions from this sort of research, Dr. Van den Bulck said. However, the idea that adolescents use their phones because they can't sleep does not hold here because of the two-way communication involved. It would apply to outgoing calls, but not to incoming calls.

Unless there were clusters of sleepless adolescents, it is more likely that communicating children keep each other awake, Dr. Van den Bulck wrote.

Mobile-phone use after lights out is widespread, he said. The risk ratios suggest that there is no safe dose. Even moderate use doubles the risk of long term tiredness, nor is there is a safe time to send or receive calls or messages.

There is growing awareness of the importance of studying the impact of the modern electronic media on several aspects of adolescent health in general and sleep in particular, Dr. Van den Bulck said.

The American Academy of Pediatrics has suggested that children's bedrooms ought to be "electronic media-free." However, the Academy appeared to be thinking mainly of media such as TV and video games, he said.

However, the present study suggests that there are many more threats to adolescent sleep in the bedroom. As mobile phones become ever more complex (integrating radio, television, and MP3 technologies), the attraction to use them after lights out is likely to increase further, Dr. Van den Bulck concluded.