subject: Alzheimer's Medication May Affect both Sleep and Depression [print this page] Alzheimer's Medication May Affect both Sleep and Depression
Psychologist Donna Giles, PhD, has been studying the link between sleep and depression at the University of Rochester Medical Center. She's discovered that those with a family history of depression and a particular type of sleep pattern called shortened REM latency are twice as likely to become depressed as family members without the same sleep pattern.
In a normal sleep pattern we cycle through four or five periods of deepening sleep a night. REM (rapid eye movement) or dream sleep is the last of these five cycles. REM sleep is a period of deep sleep characterized by increased brain activity, rapid eye movements and muscle paralysis (to prevent us acting out our dreams). The sleep pattern the research team has linked to depression is one of shortened REM latency the time between when we fall asleep and when we begin dreaming. Commonly, the length of time between falling asleep and entering a dream state is about 90 minutes. Those with shortened REM latency will begin dreaming less than 60 minutes after falling asleep.
Shortened REM latency runs in families, and seems to be a marker for vulnerability to depression. About 30 to 40 percent of depression outpatients and 60 to 70 percent of depression patients treated in hospital have short REM latency, compared to about 20 percent of non-depressed people. "This is the first physiological marker that predicts the onset of depression even in someone who has never had the illness, says Giles. Unfortunately, there is no diagnostic test for short sleep latency. "You wouldn't know you have it unless you were tested in a sleep laboratory," explains Giles, "Your sense of time is all mixed up when you sleep, so you can't really remember how fast you fell asleep and started dreaming."
Giles and her colleagues are now studying the effects of Aricept (donepezil hydrochloride), the prescription medication given to Alzheimer patients to improve their memory, awareness and mental functioning, on sleep patterns. Aricept increases the amount of the brain chemical acetylcholine, which is involved in both sleep and memory. The theory is that people who quickly cycle into dream sleep are more sensitive to acetylcholine. If that's the case, the researchers hypothesize, the brain chemical may play a role in predisposing people to depression.
