Need help with a flagging memory? Fuzzy thinking? You may want to skip the expensive and likely ineffective memory supplements and concentrate on improving your sleep habits instead. The health benefits of a proper night’s rest have been shown to help numerous conditions, from hypertension to diabetes and depression. Increasing evidence points to the importance of good-quality sleep in keeping your memory and cognitive abilities sharp, too.
The biology of memory
While the biological explanation of how memories are formed and retained is still evolving, evidence suggests that sleep is especially crucial in the second step of creating a lasting memory: consolidating information.
Researchers have found that sleep plays an important role in the consolidation of declarative and procedural memories by increasing the links between individual nerve cells in the brain during sleep. Declarative memories are those related to names, dates, faces, facts, and specific events, while procedural memories are those that deal with skills you acquire (like playing an instrument or riding a bicycle).
Various studies have shown that people recall data pertaining to words, images, and motor tasks better if they sleep soon after obtaining the information.
Sleep and cognitive impairment
Intriguing findings on the relationship between sleep and cognitive impairment have also come to light. The following are a few of the recent highlights:
• Too little or poor-quality sleep may be linked to Alzheimer’s disease, according to a 2013 report in JAMA Neurology. Investigators from Johns Hopkins and the National Institute on Aging studied data from 70 community-dwelling older adults (average age, 76 years) participating in the Baltimore Longitudinal Study of Aging—Neuroimaging study (BLSA-NI). At the start of the BLSA-NI, all participants were free of cognitive impairment.
During the study, they underwent a special type of neuroimaging test known as PiB PET to measure the amount of beta-amyloid plaque that had accumulated in their brains. These dense clumps of proteins are a hallmark of Alzheimer's. Participants also answered questions about their sleep patterns, including queries about how long they slept and whether they considered their sleep to be very sound and restful, very restless, or somewhere in between.
The investigators found that people who reported shorter sleep duration (no more than six hours) and who described their sleep as restless had more plaque buildup than participants who reported sleeping longer and having a more sound and restful sleep. Additional studies will be necessary to determine whether the protein clumps cause poor sleep or are the result of it, and whether improved sleep can prevent or slow Alzheimer's progression.
• Findings from the authors of a separate 2013 report in JAMA Neurology suggest that a good night’s sleep might reduce the increased risk associated with a genetic predisposition to Alzheimer’s disease.
As a part of the Rush Memory and Aging Project, researchers looked at the relationship between poor sleep consolidation (defined as sleep interrupted by repeated awakenings) and the risk for Alzheimer’s disease associated with the APOE e4 risk allele in 698 community-dwelling people (average age, 82 years) who did not have dementia.
For 10 days, study participants wore special monitors that detected wrist movement, a surrogate measure of fragmented sleep. The patients were then followed for three to six years and underwent annual neuropsychological testing. During that time, 98 of the participants developed Alzheimer’s disease and 201 died.
The researchers found that among the fitful sleepers, people who carried the APOE e4 allele were four times as likely to develop Alzheimer’s disease as noncarriers. This finding was not surprising because a person with one copy of this allele has a three to four times greater risk of developing Alzheimer’s disease than a person without it. But the researchers also discovered that APOE e4 carriers who slept well were only twice as likely to develop the disease.
Again not surprisingly, autopsies of the deceased participants’ brains revealed the presence of far more neurofibrillary tangles in the brains of APOE e4 carriers than in those of noncarriers. Interestingly, however, the tangles were more dense in the poor sleepers.
• An experiment in mice, reported in 2013 in Science, suggests that sleep helps restore the brain by flushing out toxins that accumulate while we are awake. The researchers injected beta-amyloid into the mice and measured how long it lasted while the mice were awake and during sleep. The beta-amyloid disappeared twice as fast from the brains of the mice when they were sleeping.
Sleep and aging
Experts recommend that older adults get seven to eight hours of sleep each night for overall good health and optimal functioning. Unfortunately, that may be easier said than done because sleep patterns change with age, and older individuals report more problems in getting to—and staying—asleep.
According to the National Institutes of Health, nearly half of people age 60 or older report insomnia. In addition, their sleep is not as deep as it was at a younger age, and they tend to wake more often during the night. Chronic pain, increased sensitivity to noise, and medical problems like obstructive sleep apnea (which causes periodic short stops in breathing during sleep) and restless leg syndrome also rob older individuals of restorative sleep.
If you’re having trouble sleeping, a good first step is to be sure you’re practicing good sleep hygiene (or habits). The American Academy of Sleep Medicine recommends the following:
• Try to establish and stick to a routine sleep schedule.
• Avoid napping, if possible. If not, don’t nap after 3 p.m. and do limit your nap to less than one hour.
• Avoid caffeine in the afternoon and evening, and limit or avoid alcohol.
• Refrain from watching TV, or reading, in bed.
• Try to deal with any worries and concerns during the day and let them go at night.
• Establish a bedtime ritual. Try a light snack, a warm bath, or some other soothing activity each night before you go to bed.
• Keep the bedroom dark, quiet, and on the cool side.
• Get out of bed if you can’t fall asleep and find a quiet activity to do until you feel sleepy.
Sleeping pill precautions
Be aware that sleeping pills can affect your memory and cognitive abilities. This is particularly true with benzodiazepine-type sedatives, such as diazepam (Valium), temazepam (Restoril), lorazepam (Ativan), oxazepam (Serax), and alprazolam (Xanax and others). Medications in this class, whether short-, intermediate- or long-acting, have been shown to increase the risk of cognitive impairment and delirium in older adults. Consequently, the American Geriatrics Society recommends that drugs in this class not be used for the treatment of insomnia in seniors.
Short-term memory loss has been linked to the over-the-counter antihistamine diphenhydramine (Benadryl), which is also an ingredient in sleep aids such as Tylenol PM and Unisom.
Newer sleep medications, including zolpidem (Ambien and others), eszopiclone (Lunesta), and ramelteon (Rozerem), have come under scrutiny because of reports that some people have experienced incidents like walking, eating, or even driving while sleeping during the first few hours after taking the medication, yet having no memory of it the next day. These drugs carry warnings about the possibility that such incidents may occur.
As a further precaution, the the Food and Drug Administration warns people who take zolpidem extended-release (Ambien CR)— either 6.25 mg or 12.5 mg—not to drive or engage in other activities that require complete mental alertness the following day because levels of the drug can remain high enough to impair these activities.
Learn more about nondrug options for getting better sleep.