Over the past two decades, the amount of time spent engaging with screens (screen time) has rapidly increased as technology progresses and the world becomes increasingly digital. Reports of insomnia, characterized by delayed sleep onset and night waking, have increased in tandem. This article considers the association between the two and suggests three potential mechanisms that may explain the link.
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The normalization of screen time
Screen time is defined as the amount of time spent looking at, or interacting with, an electronic device with a screen and includes televisions, computers and smart devices such as telephones or tablets. The growth of the internet and the introduction of mobile computing devices, followed closely by tablets and smartphones, have seen these technologies become increasingly integrated into everyday life.
In line with increased ownership, devices have increased in both affordability and portability. As such, they are increasingly used in the immediate time before trying to sleep. Screen time at bedtime is not a new phenomenon: television watching before sleep has grown in popularity to become the norm across the past fifty years.
Newer technologies such as smartphones and video gaming systems are rapidly gaining similar status. However, unlike television screen use, which is passive, these devices have interactive properties that are more stimulating and more likely to capture attention.
Although these trends are reported across the lifespan, children and adolescents who have been born into a world of digital communication and entertainment, so-called ‘digital natives’, are significantly more likely to choose forms of active screen use (such as playing video games or using social media) than the passive forms favored by older generations.
Commensurate with the normalization of screen time in the bedroom has increased the prevalence of insomnia (defined as difficulty in falling and remaining asleep), amongst children and young people (CYP).
Insomnia is common among CYP. In one American large-scale sleep survey in 2013, 77% of adolescent respondents reported sleep difficulties, including night waking and difficulty falling asleep. The same age group also displayed notable coping mechanisms, with 60% using caffeinated beverages and 53% taking weekday naps to compensate for lack of sleep.
Rates of insomnia in CYP also appear to be increasing. Rates of hospitalization for insomnia in those aged 16 and under in the United Kingdom doubled between 2012 and 2019, and prescriptions for the sleep-inducing hormone melatonin increased by 25% in the same period. A longitudinal study of sleeping patterns of school-aged children in Australia found a reduction in approximately 30 mins' sleep duration across a 20-year period.
The association between screen time and insomnia
Consistent findings from community-based samples confirm that screen time and insomnia among CYP are rising in parallel. This has led to a considerable body of research that considers the association between the two, with the following findings:
- Screen use in the final hour before attempting to sleep is associated with shorter overall sleep duration and extended sleep onset latency;
- The prevalence of night-waking due to interruptions from the screen device (social media messaging, notifications, text messages, etc.) is common and associated with daytime exhaustion;
- The likelihood of insomnia is increased if multiple screens are present in the bedroom.
Although such findings are consistent across many studies, most of those conducted have been cross-sectional and therefore cannot rule out reverse causality. While it is assumed that screen time leads to insomnia, it is also possible that those with sleep disturbances are more likely to engage in screen time before bed.
One recent study addressed this with a prospective cohort design and found that adolescents who reported high amounts of screen time were twice as likely to experience sleep difficulties across a twelve-month period. Those who reported nocturnal wakening due to cell phones were three and a half times more likely to experience insomnia than those who did not.
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How does screen time affect sleep?
Although the causality between insomnia and screen time is difficult to determine, three potential mechanisms that may link screen time and sleep disturbance have been suggested.
Delayed sleep onset
This is a behavioral delay of sleep whereby children and young people delay the onset of sleep in lieu of prolonging screen entertainment. This time-displacement effect particularly truncates total hours spent sleeping on weekdays when staying awake later cannot be offset by later waking.
Screen time that is more interactive and psychologically stimulating has a more deleterious impact on sleep than less thrilling and more passive forms of screen time. However, it is highly likely that this effect is not linear: stimulating screen time increases physiological arousal, which disrupts sleep.
Violent or exciting video games are associated with increased heart rate and blood pressure, which are associated with delayed sleep onset. One controlled laboratory study found that participants who played video games shortly before attempting to sleep reported lower subjective sleepiness, longer sleep latency and reduced rapid eye movement (REM) sleep compared to those who did not play such games.
Exposure to any light suppresses the natural production of melatonin in the body. Still, numerous studies have shown that the specific light (short-wavelength blue light) emitted from digital devices' screens are particularly disruptive.
One study compared exposure to blue and green light and found that the blue light suppressed melatonin's secretion for twice as long as a green light. Another study compared melatonin secretion between participants who wore blue-light-blocking goggles while exposed to bright light to participants without goggles exposed to dim light. Both groups exhibited similar melatonin production, strengthening the blue light-melatonin hypothesis.
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