Elderly people who are sleepy during the day or who do not feel like doing activities due to sleep problems are more likely to develop a syndrome that can lead to dementia. This is according to a study published in the online edition of Neurology®, the medical journal of the American Academy of Neurology. People with this syndrome walk slowly and report that they have memory problems, even though they have neither walking impairment nor dementia. The so-called “motor cognitive risk syndrome” can occur before dementia develops. The study found that people with excessive daytime sleepiness and a lack of motivation to get things done were more likely to develop the syndrome than people without these sleep-related problems. The study does not prove that these sleep-related problems cause the syndrome, it just shows a link, and there is a possibility that people can get help with their sleep problems and prevent later cognitive decline.
Daytime Sleepiness and Dementia
The study involved 445 people with an average age of 76 who did not suffer from dementia. At the beginning of the study, the participants completed questionnaires on the subject of sleep. They were asked about memory problems and their walking speed was tested on a treadmill at the beginning of the study and then once a year over an average period of three years. The sleep assessment included questions such as how often people had trouble sleeping because they woke up in the middle of the night, couldn’t fall asleep within 30 minutes or felt too hot or too cold, and whether they were taking medication to help them sleep. The question assessing excessive daytime sleepiness asks how often people had trouble staying awake while driving, eating or engaging in social activities.
The question on enthusiasm asks how much of a problem people had getting enough enthusiasm to get things done. In total, 177 people met the definition of poor sleepers and 268 met the definition of good sleepers. At the beginning of the study, 42 people had motor-cognitive risk syndrome. A further 36 people developed the syndrome during the study. Of those with excessive daytime sleepiness and lack of enthusiasm, 35.5% developed the syndrome, compared to 6.7% of those without these problems.
After accounting for other factors that could influence the risk of the syndrome, such as age, depression and other health conditions, the researchers found that people with excessive daytime sleepiness and lack of enthusiasm were more than three times as likely to develop the syndrome as people who did not have these sleep-related problems. However, more research needs to be done to investigate the link between sleep problems and cognitive decline and the role of motor-cognitive risk syndrome. One limitation of the study is that participants reported their own sleep information, so they may not have remembered everything accurately.
Deep Sleep as Dementia Prevention
According to one study , even a 1% reduction in deep sleep per year leads to a 27% increased risk of dementia in people over the age of 60. This suggests that promoting or maintaining deep sleep, also known as slow-wave sleep, could prevent dementia in old age. The study, led by Associate Professor Matthew Pase of the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health in Melbourne, Australia, looked at 346 participants over the age of 60 who took part in the Framingham Heart Study and participated in two overnight sleep studies between 1995 and 1998 and between 2001 and 2003, with an average of five years between the two studies.
These participants were then carefully screened for dementia from the time of the second sleep study until 2018. The researchers found that the amount of deep sleep decreased on average between the two studies, indicating a loss of slow-wave sleep with age. Over the next 17 years of follow-up, there were 52 cases of dementia. Even after accounting for age, sex, cohort, genetic factors, smoking status, use of sleep medications, antidepressants and anxiolytics, each percentage decrease in deep sleep per year was associated with a 27 percent increase in dementia risk.
Deep sleep supports the aging brain in a variety of ways, and sleep is known to promote the removal of metabolic waste from the brain, including facilitating the removal of proteins that accumulate in Alzheimer’s disease. Until now, however, researchers were not sure what role deep sleep plays in the development of dementia. The findings suggest that loss of deep sleep may be a modifiable risk factor for dementia. According to Associate Professor Pase, the Framingham Heart Study is a unique community-based cohort with repeated overnight polysomnographic (PSG) sleep studies and uninterrupted monitoring for emerging dementia.
The researchers also investigated whether a genetic risk for Alzheimer’s disease or brain volume indicative of early neurodegeneration could be associated with a reduction in deep sleep. They found that a genetic risk factor for Alzheimer’s disease, but not brain volume, may be associated with an accelerated decline in deep sleep.
Sleep Disorders Associated With Cognitive Impairment
Other research adds to the growing body of evidence on sleep disturbance and cognitive impairment, showing significant associations between three measures of sleep disturbance and the risk of developing dementia within ten years. The findings, published in the American Journal of Preventive Medicine, published by Elsevier, link sleep disturbances (difficulty falling asleep within 30 minutes) and the use of sleep medications with a higher risk of developing dementia. The researchers also found that people who reported having difficulty falling asleep and staying asleep (difficulty falling back asleep after waking up) were less likely to develop dementia over the course of the study.
This study is novel because it is the first to examine how long-term sleep disturbances relate to dementia risk using a nationally representative sample of older adults in the US. Previous studies have linked REM sleep behavior, sleep deprivation (less than five hours of sleep) and the use of short-acting benzodiazepines to cognitive impairment. The findings of the study on insomnia with sleep-through disturbances support other recent studies using smaller, separate data samples. This study included only individuals who were free of dementia at baseline in 2011.
There is no cure for dementia and recent pharmaceutical approaches to treating dementia have had limited success, pointing to the importance of preventive approaches to dementia. “By focusing on variations in sleep disturbances, our findings may help provide information about lifestyle changes that can reduce dementia risk,” explained co-researcher Margaret Anne Lovier, MPH, Department of Public Health and Preventive Medicine, SUNY Upstate Medical University, Syracuse, NY, USA. The mechanism for the lower risk of dementia in people with insomnia caused by sleep deprivation is still unknown. However, the researchers hypothesize that greater engagement in activities that maintain or increase cognitive reserve could reduce the risk of dementia.
Recent evidence suggests that sleep disorders are more common in older adults than in other age groups. This could be due to a variety of factors, including fear of the COVID-19 pandemic or warmer nights as a result of climate change. Older adults suffer from sleep disorders due to a variety of issues. Further research is needed to better understand the causes and manifestations and to limit the long-term consequences. These findings emphasize the importance of considering the history of sleep disturbances when assessing the dementia risk profile of older adults. Future research is needed to examine other measures of sleep disturbance using a national longitudinal sample to determine whether these findings on sleep disturbance and dementia apply to specific dementia subtypes and how certain sociodemographic characteristics may interact with sleep disturbance to influence dementia risk.