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    A look at adolescent sleep needs

    Waking up to the unique sleep needs of adolescents

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    Teenagers generally require 8.5 to 9.5 hours of sleep per night.1 The National Sleep Foundation (NSF) 2006 Sleep in America Poll revealed that adolescents report sleeping 7.6 hours on school nights, even though they feel that they need an average of 8.2 hours of sleep for optimal daytime function.2

    More than 50% of teenagers feel sleepy during the day.2 Only approximately 20% of all surveyed adolescents (6th- to 12th-graders) report an adequate amount of nightly sleep (=9 hours per night); among high school students (9th- to 12th-graders), the percentage decreases to 9%, suggesting that sleep deprivation is more common in older adolescents. Interestingly, 90% of parents believe that their adolescent gets enough sleep on most school nights.

    Adolescent sleep physiology

    Circadian rhythms organize the timing of various biologic processes, including sleep regulation. Light is the main environmental stimulus that synchronizes the intrinsic human circadian period to the 24-hour day. Melatonin, a hormone secreted by the pineal gland, induces evening drowsiness and also maintains the inherent sleep-wake cycle. Light blocks the secretion of melatonin; therefore, light exposure at bedtime can delay sleep initiation. Advanced Tanner stage has been associated with a delay in melatonin secretion in adolescents aged 11 to 14 years.3 In addition, adolescents seem to have a longer circadian period (24.3 hours), and difficulty entraining their sleep-wake cycle to the 24-hour solar day causes circadian phase delay or a "night owl" tendency to stay up late at night.4 This circadian alteration during adolescence has been observed across various cultures throughout the world and even across several mammalian species.5

    Sleep-wake homeostasis refers to the buildup of "sleep drive" throughout the day. A prolonged period of wakefulness increases the intrinsic need for sleep, or sleep pressure. Taking a nap in the afternoon affects sleep homeostasis by decreasing this drive to sleep, thereby delaying sleep onset at bedtime. Adolescents with more advanced Tanner stage have a slower accumulation in sleep pressure compared with younger, less mature adolescents.6 This pubertal decrease in sleep drive may promote delayed sleep initiation in teenagers.


    Figure 1: Adolescent sleep need. Adolescents may accrue a 2-hour sleep debt each school day. Data from the National Sleep Foundation.2
    Together, the circadian timing and homeostatic sleep systems regulate the sleep-wake cycle.7 Developmental changes in both systems contribute to the struggle to fall asleep at night during adolescence. The combination of difficulty initiating sleep and the adolescent sleep need (=9 hours per night) yields chronic sleep debt and daytime sleepiness for many teenagers (Figure 1).2

    Sleep behaviors

    Based on the 2006 NSF poll, most adolescents (97%) have an electronic device in their bedrooms.2 Seventy-six percent of adolescents report watching television within an hour of bedtime. One study found that among adolescents aged 12 to 18 years, 82% watched television and 55% used their computers after 9 PM.8 Other nighttime activities include watching DVDs, cell phone use, and playing video/computer games. It has been hypothesized that adolescents experience an exaggerated response to the circadian phase-delaying effects of nighttime light exposure; therefore, light stimulation associated with use of electronics close to bedtime may exacerbate their natural night owl tendency.5


    Table 1: Caffeine content chart
    Caffeine consumption is highly prevalent among adolescents. The 2006 NSF poll found that 31% of adolescents who reported drinking 2 or more caffeinated beverages per day were more likely not to sleep enough on school nights compared with those who drink 1 or fewer.2 Of 191 middle school students, average caffeine consumption was 52.7 mg per day, and 19% of students consumed more than 100 mg per day. Students may be unaware of the caffeine content of many commonly consumed beverages and over-the-counter medications (Table 1).9 Increased caffeine consumption in this cohort correlated with a later bedtime, more disrupted sleep, and daytime sleepiness.10 In healthy adults, the elimination half-life of caffeine is 5 hours; therefore, caffeine lingers in the body well after consumption and can affect sleep.11

    Other activities that keep teenagers up at night include evening homework, extracurricular activities (eg, athletics), jobs, and socializing. Adolescents who work 20 or more hours per week attain less sleep, tend to oversleep more on school days, and report increased use of caffeine, alcohol, and tobacco compared with adolescents who work fewer than 20 hours per week.12 Parental influence on setting bedtimes dramatically decreases as adolescents get older. Adolescents who have a curfew get to sleep earlier, wake up earlier in the morning, and have less daytime sleepiness.

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    Poll