Sleep and Aging

Aging is associated with malfunction or decrease in sensitivity of the SCN to environmental cues to adjust circadian rhythm to a natural 24-hour day/night cycle.

Up to 50% older people (> 65 years of age) tend to get tired earlier, wake up earlier. Many people in their 60’s and 70’s find themselves going to bed at 6to7 pm and waking at 3 to 4 am in the morning. In the 70’s and 80’s, the circadian rhythms tend to flatten out and often lose the ability to maintain a functional sleep-wake cycle. This phenomenon is most notable in elderly care facilities where residents may sleep at any hour of the day or night, often for a portion of every hour. I.e. On average, the nursing home patient is never asleep for a full hour and never awake for a full hour. Rather, the patient is constantly falling asleep and waking up. (Eus J. W et al. Ageing Research Reviews 2002, 1(4): 721-778; Ancoli-Israel S. Geriatrics 1997, 52: 20-30).

If the elderly person suffers from dementia, sleep may be more erratic and problematic.

Changes in sleep architecture and circadian rhythms, including increased sleep latency and nighttime awakenings, decreased slow-wave sleep, rapid eye movement sleep, and total sleep time, and increased daytime napping are widespread in people with dementia. In addition, cyclic agitation episodes ("sun downing"), nightmares or hallucinations, sleep attacks, and nocturnal behavioural outbursts are associated with specific dementia syndromes. (McCurry SM et al. Current Treatment Options in Neurology 2003;(3): 261-272) Compared to normal sleep cycles the elderly have more fragmented poor quality sleep. Slow wave sleep is reduced indicating poor rejuvenation of tissues as growth hormone secretion is reduced. There is an increased in stage 1 and 2 sleep with more fragmented REM sleep indicating more dreaming. Age related changes in sleep are due to weaker circadian regulation of sleep and wakefulness. Manipulation of the circadian timing system, rather than the sleep homeostat, offers a potential strategy to alleviate age related decrements in sleep and daytime alertness levels. [Kales and Kales. N. Engl. J. Med.1974; 209:487-499; Cajochen C et al. Chronobiology International 2006, 23(1-2): 461-474]

In summary the aged can experience the following:

• Increased napping through out the day
• Increased sleep latency
• Increase in awakenings and arousals
• Decreased stage 3 and 4 sleep (slow wave sleep)
• Increased stage 1 sleep. Stage 2 sleep is variable.
• Decreased REM sleep. REM sleep appears to be equally distributed through sleep cycles. I.e. there is no increase in REM at the end of the sleep period.
• Reduced sleep efficiency
• Increased stage shifts
• Fewer cycles
• Phase advancement
• Decreased melatonin levels