According to a new UK study, health older adults without sleep disorders can have a reduced “sleep need” and are less sleepy during the day than healthy young adults.
Researchers discovered that during a night of eight hours in bed, total sleep time decreased significantly and progressively with age.
Older adults slept about 20 minutes less than middle-aged adults, who slept 23 minutes less than young adults.
The number of awakenings and the amount of time spent awake after initial sleep onset increased significantly with age, and the amount of time spent in deep, slow-wave sleep decreased across age groups.
Yet even with these decreases in sleep time, intensity and continuity, older adults displayed less subjective and objective daytime sleep propensity than younger adults.
The study is found in the Feb. 1 issue of the journal SLEEP.
Two additional nights involving experimental disruption of slow-wave sleep led to a similar response in all age groups. Daytime sleep propensity increased, and slow-wave sleep rebounded during a night of recovery sleep.
According to the authors, this suggests that the lack of increased daytime sleepiness in the presence of an age-related deterioration in sleep quality cannot be attributed to unresponsiveness to variations in homeostatic sleep pressure.
Instead, healthy aging appears to be associated with reductions in the sleep duration and depth required to maintain daytime alertness.
“Our findings reaffirm the theory that it is not normal for older people to be sleepy during the daytime,” said principal investigator Derk-Jan Dijk, PhD, professor of sleep and physiology at the University of Surrey in the U.K.
“Whether you are young or old, if you are sleepy during the day you either don’t get enough sleep or you may suffer from a sleep disorder.” Authorities estimate 30 million Americans alone have a disordered sleep pattern.
The authors noted that the cause of the age-related reductions in slow-wave sleep and sleep need still must be established. Related factors could include alterations in reproductive hormones or changes in the brain.
They added that the study did not address sleep propensity during the evening hours, when it is possible that older adults may be sleepier than young adults.
According to the authors, the study has implications for the treatment of insomnia in older adults, who may be unaware of their reduced sleep need.
For these adults, sleep restriction and an awareness of the reduced need for sleep may be a successful behavioral therapy for insomnia in healthy older adults.