Older people may need less sleep

It has long been known that aging is associated with a reduced capacity for sleep.  Now, researchers at Brigham and Women’s Hospital (BWH) have shown that when older people are asked to stay in bed during 16 hours of darkness, they sleep only about 7.5 hours compared to the 9 hours that younger people sleep when in the same situation.  This research is published online in Current Biology, a Cell Press publication, on July 24, 2008.

“These results have two possible interpretations,” said Elizabeth Klerman, MD, PhD, a physician and researcher in the Division of Sleep Medicine at BWH.  “Older people may need less sleep or they may sleep less because of age-related changes in the ability to fall asleep and remain asleep.”

Klerman and her colleague, Dr. Derk-Jan Dijk, of the University of Surrey in the UK, evaluated the capacity for sleep in young people, between the ages of 18 and 32, compared to older people, aged 60 to 72, by monitoring healthy individuals taking no medication and having no medical conditions or sleep disorders.  Researchers controlled for circadian rhythms (the body’s natural sleep/wake cycle) by allowing the chance to sleep both during the night and day and by also controlling sleep opportunities.  Researchers found:

• If they previously spent the same amount of time in bed, older people took a longer period of time to fall asleep than younger people.
• After spending several days during which they were required to stay in bed for 16 hrs/day, older people slept, on average, 1.5 hours less than younger people.
• The difference in sleep time was split evenly between rapid eye movement (REM), or sleep associated with dreaming, and non-REM sleep.
• Most younger subjects slept longer than their usual self-selected sleep times.

Klerman also notes that, “Younger people frequently do not get as much sleep as they need, and there are many health and safety problems associated with too little sleep.”

These findings may influence clinical treatment in older people, as insomnia – being awake when wanting to be asleep – is a frequent complaint in older age groups.

“If older people believe that they need more sleep than they can achieve even when they spend extra time in bed, then they may complain of insomnia and could start taking medications needlessly,” Klerman said.  “Older people may need to be evaluated for a sleep disorder if they are tired during the day.”

The researchers encourage more investigation into this area of age-related changes in sleep and the problems associated with insufficient sleep. 

(Source: Current Biology: Brigham and Women’s Hospital: July 2008)