Sleep and How It Affects Memory and Cognition

Ricardo Osorio, M.D., MA

With 10 percent of adults over age 65 now suffering from Alzheimer’s disease (AD), and other dementias (this number is projected to double by 2050) understanding the factors responsible for cognitive impairment is of great importance. Disturbed sleep may be one of these factors. In multiple studies observing large groups of peoples, changes in the number of hours of sleep and sleep disturbances, mainly waking during the night, as well as the presence of obstructive sleep apnea (OSA) have been associated with increased risk of cognitive decline, while better sleep patterns seem to be protective.

Sleep provides time for important things to happen inside of the brain. For instance, the processing of memories occurs throughout sleep. It is during this time that memories are stored so they can be retrieved while awake. Sleep also keeps the brain from overloading, it clears the brain from harmful toxins, and performs other functions ensuring that humans awaken with brains that are refreshed and ready to tackle new challenges.

As we age, however, sleep changes dramatically. With age, the quality of sleep decreases and becomes more fragmented, and there is an increase in the prevalence of OSA. Older people tend to become sleepier in the early evening and wake earlier in the morning compared to younger adults. Older age is also associated with medications that might disrupt sleep. Many older adults, though certainly not all, report being less satisfied with sleep.

Good sleep quality is beneficial for memory and cognition, but whether these age-related changes in sleep contribute to the changes in cognition commonly observed in older adults, or to the increased risk for developing Alzheimer’s Disease, is unknown. Recent studies in mice and humans suggest that this could be the case. Sleep could, in addition to its beneficial aspects in reducing stress and improving cardiovascular (heart) health and metabolism, be also helpful due to both lower production of and increased removal of harmful substances in the brain that build up during the day.

Improving sleep remains a reasonable recommendation that we can offer to members of the public who strive toward better brain health and successful aging.

Ricardo S Osorio is a Research Assistant Professor of Psychiatry at NYU Center for Brain Health (CBH). At CBH, Dr. Osorio’s focal area of research interest is the use of neuroimaging and cerebrospinal fluid biomarkers to assist in the study of sleep disturbances as risk factors for cognitive impairment in aging and for dementia.

Dr. Osorio also collaborates with researchers from the Mount Sinai Health System Integrative Sleep Center and the NYU Center for Neural science in the NYU Sleep, Aging, and Memory (SAM) Lab. The SAM Lab investigates why we sleep, what happens to the brain during sleep, and the consequences of disturbed sleep on the brain. Its mission is to solve these, and other issues related to sleep, normal aging, memory processing, and the risk for Alzheimer’s disease.

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