New study sheds light on the connection between sleep disturbances and dementia risk

If you’re feeling unusually sleepy throughout your day as you age, it’s worth considering that this fatigue may signal a higher risk of developing a condition that could ultimately lead to dementia, according to new research.

In the study, 35.5% of participants who had excessive daytime sleepiness and a lack of motivation went on to develop motoric cognitive risk syndrome, compared to just 6.7% of those without these issues, as reported in the journal Neurology on Wednesday.

Motoric cognitive risk syndrome (MCR) is characterized by slow walking speed and memory concerns among older adults who don’t yet have dementia or mobility impairments. Those with MCR are more than twice as likely to develop dementia, a syndrome first identified in 2013.

Dr. Victoire Leroy, assistant professor of geriatric medicine at Tours University Hospital in France, noted via email, 'Previous studies have highlighted the connection between sleep disorders and an increased risk of dementia.'

Some previous scientific studies explored the connection between sleep and dementia, but often at a single point in time. According to the research team, little has been known about how specific poor sleep patterns relate to pre-dementia conditions, prompting them to broaden the scope of this field of study.

'Understanding the link between sleep disturbances and the risk of motoric cognitive risk syndrome (MCR) is crucial, as early intervention could be key to preventing dementia,' the authors emphasized.

Monitoring sleep patterns

The findings are based on data from 445 adults, averaging 76 years old, recruited from Westchester County, New York, as part of the Central Control of Mobility and Aging study, which examines cognitive and brain functions related to aging mobility. Participants had their walking gait recorded on treadmills and were followed up annually from 2011 to 2018.

The researchers also gathered annual reports from participants about their sleep quality and duration over the two weeks preceding each assessment. They collected insights across seven components of the Pittsburgh Sleep Quality Index: overall sleep quality, time to fall asleep, total sleep duration, sleep efficiency, sleep disruptions, use of sleep aids, and daytime issues like difficulty staying awake or reduced enthusiasm for daily activities.

Over an average follow-up period of about three years, 36 participants developed motoric cognitive risk syndrome. While 'poor' sleepers had only a slightly elevated risk of MCR compared to 'good' sleepers, a closer look at the seven sleep components revealed that daytime dysfunction was linked to a 3.3-fold increase in MCR risk.

The study's findings could encourage both doctors and patients to ask more questions about sleep patterns and to pay closer attention to walking speed when diagnosing potential risks, according to Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida. Isaacson was not involved in the study.

The connection between sleep and cognitive decline

Dr. Tara Spires-Jones, professor of neurodegeneration and director of the Centre for Discovery Brain Sciences at the University of Edinburgh, pointed out several key limitations of the study via email.

'The sleep data was self-reported rather than scientifically measured, and such self-reports may be influenced by memory problems,' said Spires-Jones, who was not involved in the study. 'Additionally, the study participants were mostly white, and the sample size was smaller than similar studies conducted at a single time point, so the findings would benefit from validation in larger future studies.'

While the study authors noted that their three-year follow-up period is longer than some previous studies, they acknowledged that the duration is still relatively short.

Motoric cognitive risk syndrome is a newly recognized condition, and experts are still working to understand its causes and impacts on the body. This challenge is compounded by the absence of definitive pathological biomarkers for MCR, according to Isaacson.

'Several mechanisms could help explain this connection,' Leroy explained. 'Sleep is involved in clearing neurotoxins that build up in the brain. Additionally, previous research has found a higher buildup of proteins linked to Alzheimer's disease in people who experience sleep deprivation.'

'Another potential explanation is the activation of the brain’s inflammatory response, which is seen in Alzheimer’s disease and related dementias,' Leroy added.

Experts are puzzled as to why, among the seven sleep components, daytime dysfunction was the only one strongly linked to MCR risk. It might be expected that other factors like sleep quality and quantity would also play a role in daytime issues, they said.

Spires-Jones highlighted that when considering the potential link between daytime dysfunction and MCR, reverse causation should also be taken into account.

'Scientific evidence suggests that in the early stages of dementia, brain changes disrupt sleep patterns,' she explained, emphasizing that it is 'more likely that the early stages of the disease are causing sleep disturbances, rather than the disturbances leading to the disease.'

It’s well-established that sleep disorders like REM sleep behavior disorder can serve as early indicators of conditions such as Lewy body dementia or Parkinson’s disease, according to Isaacson.

The importance of monitoring sleep health in older adults

The study underscores the critical value of sleep, according to Leroy.

Anyone experiencing sleep issues should consult their doctor, consider filling out a sleep questionnaire, and discuss whether a sleep study, either at home or in a clinical setting, might be beneficial, Isaacson advised.

'There are now various treatments, both pharmaceutical and non-pharmaceutical, that can help depending on the specific sleep issue identified,' he added. 'Addressing sleep disturbances can have long-term benefits for brain health and may play a significant role in preventing dementia over the years.'

There are additional steps you can take to safeguard your brain as you age.

'Living a healthy lifestyle — including proper nutrition, maintaining a healthy weight, staying physically and mentally active, and addressing any hearing loss — all contribute to brain resilience and likely reduce the risk of dementia,' said Spires-Jones.

'This isn't about blaming individuals with dementia for their lifestyle choices,' she clarified. 'The best estimates suggest that less than half of dementia risk is linked to modifiable factors, with the remainder likely determined by genetics.'

Given the potential to reduce your risk and the ongoing advancements in medical research and treatments, Spires-Jones expressed that there is plenty of reason for optimism.

For those already facing mobility challenges, fall prevention strategies can be effective, Isaacson suggested. This can include evaluations by physical and occupational therapists, as well as home modifications such as adding grab bars in the shower, clearing obstacles, and using night lights.