Healthy People Need Less Sleep as They Age; Seniors
Should Not Be Sleepy in Daytime
Senior citizens slept about 20 minutes less than
middle-aged adults, who slept 23 minutes less than young adults in study
Feb. 1, 2010 Healthy senior citizens without
sleep disorders can expect to have a reduced "sleep need" and to be less
sleepy during the day than healthy young adults. A new study indicates
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,
according to the study in the Feb. 1 issue of the journal SLEEP.
As we age, the lens in the eye thickens and the pupil
shrinks, reducing the amount of light passing through to the retina;
earlier study opted for gold glasses to block blue light
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.
Furthermore, 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 (state of
equilibrium) 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."
The study was conducted at the Clinical Research
Centre of the University of Surrey and involved 110 healthy adults
without sleep disorders or sleep complaints;
● 44 were young (20 to 30 years),
● 35 were middle-aged (40 to 55 years) and
● 31 were older adults (66 to 83 years).
After an eight-hour baseline sleep test, subjects
were randomized to two nights with or without selective slow-wave sleep
disruption by acoustic stimuli, followed by one recovery night.
Nighttime sleep was evaluated by polysomnography, while sleep propensity
was assessed using the Multiple Sleep Latency Test (MSLT) and the
Karolinska Sleepiness Scale.
During the baseline night, mean objective total
sleep time decreased from 433.5 minutes for young adults to 409.9
minutes for middle-aged adults and 390.4 minutes for older adults.
Average minutes of slow-wave sleep decreased from
118.4 minutes for young adults to 85.3 minutes for middle-aged adults
and 84.2 minutes for older adults. Mean number of minutes spent awake
after initial sleep onset increased from 21 for young adults to 49.9 for
middle-aged adults and 70.7 for older adults.
Objective daytime sleepiness measured by the MSLT
decreased with age. When asked to lie in a comfortable position on the
bed and try to fall asleep, young adults fell asleep in an average of
8.7 minutes, compared with 11.7 minutes for middle-aged adults and 14.2
minutes for older adults.
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 also has
implications for the treatment of insomnia in older adults, who may be
unaware of their reduced sleep need. Therefore, sleep restriction, which
leads to increased homeostatic sleep pressure, may be a successful
behavioral therapy for insomnia in healthy older adults.
About information source:
SLEEP is the official journal of the APSS, a joint
venture of the American Academy of Sleep Medicine and the Sleep Research
Society. The APSS publishes original findings in areas pertaining to
sleep and circadian rhythms. SLEEP, a peer-reviewed scientific and
medical journal, publishes 12 regular issues and 1 issue comprised of
the abstracts presented at the SLEEP Meeting of the APSS.
AASM is a professional membership organization
dedicated to the advancement of sleep medicine and sleep-related
research.
Feb. 1, 2010 Healthy senior citizens without
sleep disorders can expect to have a reduced "sleep need" and to be less
sleepy during the day than healthy young adults. A new study indicates
that during a night of eight hours in bed, total sleep time decreased
significantly and progressively with age. 
