Normal sleep with age-related changes

Modern geriatric research provides a substantial body of data on sleep parameters associated with age-related changes. Alongside normal physiological processes during aging, sleep patterns also undergo changes, independently of factors such as comorbid diseases and medication use. Normal age-related sleep mechanisms include:

• an increase in sleep time;
• a reduction in nighttime sleep duration;
• an increase in the frequency of daytime sleep;
• an increase in the number of nighttime awakenings;
• an increase in nighttime wakefulness;
• a decrease in slow-wave sleep.

In addition, circadian rhythms undergo changes, making the homeostatic mechanisms of sleep more vulnerable. It should be noted that the causes of sleep disturbances in older adults are multifactorial and depend on somatic and psychiatric conditions, social activity, cognitive status, lifestyle, and environmental influences.

More relevant information is available via Nightmares: definition, epidemiology and classification

Sleep Duration

Research data confirm that total sleep time (TST) decreases with age. However, after transition into older age groups, no further reduction in TST is observed. Assessment of sleep parameters in a group of healthy individuals showed the following total sleep durations over 24 hours:

• 10.5 hours in young people;
• 9.1 hours in middle-aged people;
• 8.1 hours in older people.

TST decreased by approximately 8 minutes per decade in men and 10 minutes in women. However, after age 60, TST stabilized and, consequently, sleep duration no longer decreased.

Sleep Initiation

Current data have confirmed that the time required to fall asleep is not dependent on age. In addition, sleep latency, which characterizes the time required to fall asleep, demonstrates only a minimal increase after age 60. Similarly minimal changes apply to the ability to fall asleep again after nighttime awakenings. Another study involving healthy individuals aged 17 to 91 years demonstrated an age-related increase in sleep latency in the 17–20-year age group and after age 50. (Floyd JA et al, 2000).

Sleep Efficiency

Sleep efficiency is an indicator defined as the ratio of total sleep time to time spent in bed, multiplied by 100%. Time in bed is measured from the moment the lights are turned off until the person gets up; part of this interval is spent awake. Sleep efficiency is considered adequate when it reaches 85%. For example, in people with insomnia, this indicator is below 75%.

Unlike all other sleep parameters, this indicator decreases significantly during adulthood and continues to increase slowly after age 60.

Sleep Maintenance

The term sleep maintenance describes the period of sleep after initial sleep onset until awakening. The phase of falling asleep, or transition from wakefulness to sleep, is called sleep onset.

A decline in the ability to maintain sleep, characterized by the arousal index (AI), is defined as the total number of awakenings per hour of sleep. The arousal index increases with age.

One important indicator of sleep maintenance is wake after sleep onset (WASO). WASO demonstrates a consistent increase of 10 minutes every 10 years from age 30 to 60 and remains practically unchanged after age 60. (Ohayon MM et al, 2004).

Sleep Maintenance

The term sleep maintenance describes the period of sleep after initial sleep onset until awakening. The phase of falling asleep, or transition from wakefulness to sleep, is called sleep onset.

A decline in the ability to maintain sleep, characterized by the arousal index (AI), is defined as the total number of awakenings per hour of sleep. The arousal index increases with age.

One important indicator of sleep maintenance is wake after sleep onset (WASO). WASO demonstrates a consistent increase of 10 minutes every 10 years from age 30 to 60 and remains practically unchanged after age 60. (Ohayon MM et al, 2004).

Sleep Stages

Healthy sleep consists of 5 cycles: four stages of slow-wave sleep and one stage of rapid-eye-movement sleep:

• stage one — 10% of total sleep duration;
• stage two — 50%;
• stage three — 25%;
• stage four — 10%;
• stage five — 15%.

Overall, slow-wave sleep (SWS) decreases with age in the adult population. Sex-related differences are also observed: men are more prone to age-related reductions in SWS.

Additional relevant facts are available via Sex-related differences in night dreams.

Daytime Napping and Daytime Sleepiness

Daytime sleep is more common among older people than among younger people. The reasons why people choose to nap during the day are quite varied. Sometimes this is related to the need to compensate for insufficient nighttime sleep, restore energy balance, or reduce daytime sleepiness. Cultural traditions have a considerable influence on daytime napping habits: daytime sleep has been a common practice among residents of China, the Mediterranean region, and Latin American countries. Some studies associate daytime napping with excessive daytime sleepiness (EDS), depression, pain, and nocturia (Foley DJ et al, 2003). EDS is not part of normal aging and may sometimes signal the presence of certain diseases.

Self-Reported Sleep Quality

People assess their sleep quality differently. One might expect older people to complain about their sleep more often than younger people. However, this is not the case. Differences may exist between self-reported assessments and objective sleep characteristics. Many sleep characteristics change with age. For example, nighttime sleep duration and sleep efficiency decrease with age, while the number of awakenings, WASO, and frequency of daytime sleep increase accordingly. However, most of these changes stop by age 60 and subsequently remain practically unchanged.

For information on age-related changes in circadian rhythms, changes in homeostasis, and hormonal regulation of sleep associated with aging, see our article “Hormonal regulation and circadian sleep rhythms with age-related changes”

References

Li J, Vitiello MV, Gooneratne NS. Sleep in normal aging. Sleep Med Clin. 2018;13(1):1-11. doi:10.1016/j.jsmc.2017.09.001.

Author: Olena Vyrva, MD

Questions & Answers

Q1. Which sleep characteristics commonly change with age?
Nighttime sleep duration, sleep efficiency, and slow-wave sleep decrease, while nighttime awakenings, WASO, and daytime napping increase. Many of these changes become relatively stable after age 60.

Q2. Is excessive daytime sleepiness considered a normal consequence of aging?
No. The article states that excessive daytime sleepiness is not part of normal aging and may sometimes indicate an underlying disease.