Poor Sleep a Cause of Cognitive Decline in Older Adults
People who suffer from poor sleep and complain of difficulties getting their brain in gear might find validation in a study by researchers at the University of Miami Miller School of Medicine which shows that too little or interrupted sleep can, eventually, lead to impaired brain function.
The study, “Effect of Sleep Quality on aMCI Vulnerable Brain Regions in Cognitively Normal Elderly Individuals,” published in the January 2019 issue of the journal, Sleep, demonstrates for the first time how lack of sleep can lead to brain atrophy in otherwise cognitively normal individuals.
“Poor sleep quality is well documented in subjects with dementia, but the relationship between sleep and dementia disorders is still poorly understood,” said Noam Alperin, Ph.D., professor of radiology and biomedical engineering at the Miller School lead author of the study. “Now, we’ve been able to show that poor sleep can actually contribute to cognitive decline in older adults.”
Participants aged 60 to 92 were rigorously evaluated using a battery of cognitive tests and a detailed clinical assessment to verify normal cognitive status, then screened for sleep quality. Relative to normal sleepers, poor sleepers exhibited significant reductions in cortical and sub-cortical volumes bilaterally in the hippocampi, as well as in the superior parietal lobules and left amygdala.
Atrophy related to poor sleep quality impacted a number of regions implicated in amnestic mild cognitive impairment (aMCI) and Alzheimer’s disease, according to Dr. Alperin.
“Our study reports that patterns of cortical and deep gray matter atrophy related to poor sleep quality impact Alzheimer’s disease-related regions of the cortex even in a population rigorously deemed unaffected by cognitive impairment, or dementia,” Dr. Alperin said.
The presence of atrophy in cognitively normal poor sleepers would suggest that sleep quality influences atrophy patterns subthreshold to symptoms of dementia, and could contribute to or facilitate further neurodegenerative processes.
“We detected changes to aMCI-related brain regions even before the onset of aMCI or other signs of cognitive decline,” Dr. Alperin said. “As such, interventions targeted towards improving sleep quality amongst the elderly may prove an effective tool for modulating the course of aMCI and Alzheimer’s disease. This opens a new window of opportunity for treatment to prevent or slow down the progress of dementia.”
Interestingly, according to Dr. Alperin, while nocturnal awakening and increased daytime sleepiness were associated with hippocampus volume loss, sleep latency and loud snoring were not. “I guess snoring does not mean poor sleep quality, at least to the snorer.”
Dementia is becoming a growing public health problem. The cost of treating dementia in the U.S. alone was estimated to be between $157 and $215 billion dollars in 2010, and it has been projected that its prevalence will double between 2020 and 2040. Alzheimer’s disease, the most common cause of dementia, generally occurs after age 70 and is often preceded by aMCI.
Faced with aging populations, the global medical community has become increasingly interested in developing interventions to slow or prevent age-related dementia disorders like Alzheimer’s disease. Characterizing the earliest stages of degenerative brain disorders is critical both for clinical risk assessment and the development of therapies to delay progression, Dr. Alperin said.
A number of cognitive and behavioral traits associated with Alzheimer’s also seem intimately tied to the disruption of circadian rhythm and sleep quality, including the troublesome phenomenon of “sundowning,” where confusion and agitation get worse towards the evening. Given that poor sleep quality negatively impacts cognitive function even in the absence of disease, sleep dysfunction has significant potential to worsen the course of clinical Alzheimer’s.
“Our study emphasizes a role for sleep intervention in fighting neurodegeneration of Alzheimer’s-related brain regions,” Dr. Alperin said. “Seven to eight hours of sleep a day seems to be important to maintain brain health in cognitively intact subjects.”
Joining Dr. Alperin in the study were co-first author John Wiltshire, M.D. 2021 candidate, Department of Radiology; Sang H. Lee, research associate, Department of Radiology; Alberto Ramos, M.D., assistant professor of clinical neurology and co-director of the Sleep Medicine Program, Department of Neurology; Rene D. Hernandez-Cardenache, Psy.D., assistant professor, Department of Psychiatry & Behavioral Sciences; Rosie E. Curiel Cid, Psy.D., assistant professor, Department of Psychiatry & Behavioral Sciences; Tatjana Rundek, M.D., Ph.D., professor of neurology, epidemiology, and public health and scientific director of the Evelyn F. McKnight Brain Research Institute; and David Loewenstein, Ph.D., professor, Department of Psychiatry & Behavioral Sciences.