How Sleep Patterns Change Throughout a Lifetime

Vital for healthy human functioning, sleep is maintained by our circadian rhythms, sleep-wake cycles occurring over 24-hour periods. Interestingly, circadian rhythms do not stay stagnant throughout a lifetime but instead change and adapt as we age.

A baby’s sleep needs are drastically different than an adult’s, while an adolescent's circadian rhythm is significantly different than someone older. You can use this information to set yourself up for best sleep practices based on your age.

Sleep architecture

Before moving into the differences in sleep between various age groups, it is important to understand the basic architecture of sleep. The architecture of sleep is a term used in academic literature and refers to normal sleep's basic structural organization. Broadly it is divided into two types of sleep:

1. Non-rapid eye movement (NREM).
2. Rapid eye movement (REM) sleep; slow-wave sleep is part of NREM.

NREM sleep is grouped into 4 stages, ranging from light to deep sleep. When sleeping, these stages appear in repeating periods, in which one sleep cycle lasts approximately 90 minutes (NREM and REM). These cycles occur anywhere from 4 to 6 times in adults each night.

Infants and babies

In comparison to other ages, babies tend to sleep significantly more throughout the day. Research indicates that infants spend approximately 17 hours asleep, not constrained to a single episode but distributed throughout the daytime and nighttime. As soon as one year after birth, a baby's sleep becomes more consolidated at night time, as they begin sleeping around 11 hours at night and three during the day. Research shows that full-term infants spend approximately 50% of their sleep in active sleep, and this percentage is cut in half by six months of age. Newborn sleep is broadly categorized as active and quiet sleep.

During active sleep, babies move, groan, and breathe irregularly. They can even open their eyes, and cry out. Quiet sleep refers to periods of relative stillness and more regular breathing. There is a limited body of literature addressing sleep and its architecture in infants, primarily due to ethical approvals and difficulties in obtaining high-quality data. But, it has been established that infants undergo many changes in their sleep in their first year of life. The circadian rhythms also develop during this period, around 4 months of age.

Adolescents

Many hormonal, developmental, and psychological changes occur during the adolescent years. Research suggests that quality sleep is extremely important during this stage of life. The prevalence of the late phenotype, meaning being a night owl, is much higher in this demographic than in other age groups.

Research suggests that sleep pressure builds up slower in adolescents, in combination with a slight delay in melatonin production. In comparison to adults, a slightly longer total sleep time is recommended, between 8 and 10 hours, but almost a third of teenagers do not get this amount, as a result of later bedtimes and early school start times. Taking this into account, teenagers experience sleep timing pressures at both the onset and end of sleep.

Adults

To maintain optimal health, cognitive functioning, and psychological well-being, the American Academy of Sleep Medicine and Sleep Research Society recommends adults sleep at least 7 hours each night. Research indicates there are some individual differences in optimal sleep duration and timing. Nowadays, many adults can more freely choose their schedules and adjust their social obligations to align with their preferred circadian rhythm.

A rule of thumb is that an individual should feel rested after sleeping, energetic throughout the day, and maintain efficient cognitive functioning. If this is the case, there is no need to worry about their amount of sleep, even though some of the broadly available sleep and activity trackers would nag otherwise. However, if one's sleep schedule and duration are inconsistent, or the total sleep time exceeds 9 hours every day, check in with your dedicated physician.

Elderly

There are several health implications due to increasing age, and sleep is no exception. Even in the case of those who are aging healthily with no ailments or diseases, the estimates are that as many as 50% of older adults experience difficulties falling asleep, maintaining sleep, and sustaining overall sleep quality.

The elderly population can suffer from more sleep fragmentation, earlier awakening hours, and reduced slow-wave sleep. Research shows these disruptions occur primarily due to the deterioration of the master clock, otherwise known as the suprachiasmatic nucleus. The neuronal changes in the SCN, aside from implications on sleep and circadian rhythms, affect learning and memory. With increasing age, the circadian rhythms shift toward an early chronotype, with early bed and wake-up times.