Risk Factors for Sleep Disturbances in Children and Adolescents

The effect of biological processes on sleep 

Two biological mechanisms affect the sleep process; sleep wake rhythm – the circadian rhythm/cycle – (the biological clock) and sleep pressure accumulation (the homeostatic cause). The two mechanisms work together and affect sleep quality, quantity and timing.

The “biological clock” is influenced by the daily cycle of secretion of the hormone melatonin which fits itself to the light-darkness changes in the environment. The melatonin is secreted when it gets dark and its level is suppressed at daybreak. Light causes suppression of melatonin secretion and therefore light exposure during the night impairs the “biological clock” and might lead to delay in bedtime and in the time of falling asleep, to excessive wakefulness during the night time and to impairment in quality and efficacy of sleep.

The homeostatic mechanism called “sleep pressure” is an endogenous (internal) biochemical mechanism regulated by the sleep control system, which creates sleep pressure as a function of the length of time that has accrued since the last episode of sleep. This means, the longer we are awake the more sleep pressure rises. This mechanism includes regulatory substances (such as adenosine) that are created during the hours of wakefulness (in the spinal fluid) and raise the sleep pressure the more they build up. This pressure is released through sleep and its level drops. It should be noted that the precise mechanism of homeostatic sleep pressure is still unknown.

Two biological processes can cause changes during sleep in children and adolescents.

• Delayed biological clock – during the adolescent period the process of melatonin secretion occurs at a later stage, which causes sleep phase postponement
• Dissipation of homeostatic sleep pressure

Changes in these two processes already begin in adolescents in middle school and constitute a challenge to their ability to fall asleep early in the evening and to get up fresh in the early morning.

The effect of environmental and psycho-social factors on sleep

There are environmental factors related to the fact that children and adolescents do not get the amount of sleep recommended for their age, which are expressed in a variety of sleep problems and disturbances.

• The lifestyle of children and adolescents might influence sleep duration and quality

Sleep duration may be affected by children’s and adolescents’ activities during the day. The time when children and adolescents wake up on weekdays is influenced by the time they start school. Delay in school starting time is related to increase in sleep duration and reduction in the level of daytime sleepiness. Middle school students in the USA who started school late reported sleeping longer including during the week, less daytime sleepiness, less difficulty concentrating and stress and higher academic performance compared to middle school students who started school earlier.

The assumption is that children and adolescents exchange their sleep time for activities such as homework, social activities and other leisure time activities. When the expectation of achievements in all these fields is high, investment of a large amount of time in these activities can affect children’s and adolescents’ sleep. In a cross sectional study from 2011 in 6247 4^th -8^th graders in China it was found that doing homework was related to reduction in duration of sleep time especially in students in the higher grades. It should be noted that parental intervention was found to be an influential factor in determining children’s bedtime and it leads to earlier bedtime and prolongation of overall sleep time.

Consumption of caffeine by adolescents is linked to shortening of sleep time, long sleep latency*, difficulty with sleeping continuously and more daytime sleepiness. High school students who reported moderate to high caffeine consumption tended to develop nearly twice as many sleep difficulties and reported more morning sleepiness than high school students who reported very low caffeine consumption. The question of whether caffeine consumption affects sleep quality or whether adolescents consume caffeine in order to contend with sleep disturbances has not yet been elucidated. (* sleep latency – time taken to fall asleep)

• Socio-economic and environmental characteristics can serve as an indicator  of sleep disturbances

Opinions are divided regarding the association between socio-economic status and gender, and sleep. There are studies that have found that children and adolescents with low socio-economic status are at higher risk of developing sleep disturbances and poor sleep quality, compared to children and adolescents from other groups. There are contradictory findings regarding the question of whether there are gender differences in various sleep indices such as total sleep time, sleep quality and sleep latency time.

• Additional factors that may affect sleep quality are physical activity around bedtime, alcohol consumption, room temperature, noise and lighting at night

Environmental noise at night is perceived as a significant cause of sleep disturbance and affects sleep architecture and quality.

The American Medical Association (AMA) published a statement in 2012 that light at night constitutes an environmental pollutant causing suppression of melatonin secretion and postponement of sleep onset and thus impairs sleep quality.

• The sharp increase in use of digital media might affect leisure time amongst children and adolescents, compete for sleep time and might impair the quality of sleep

Studies have demonstrated that the presence of digital media in children’s bedrooms, use of devices and exposure to contents before sleep are associated with postponement of lights out, reduction in sleep time, impairment of sleep quality and higher level of daytime sleepiness. Perspectives relating to the association between digital media exposure and sleep disturbances are detailed in the chapter: “The Effect of Digital Media Use on Sleep".”

*This review was prepared with the assistance and guidance of Prof. Tamar Shochat, The Faculty of Social Welfare and Health Sciences, Haifa University and Mr. Amit Green from the Assuta Health Center Sleep Institute.

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