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Wide Awake

A growing body of research connects poor sleep with dementia
April 23, 2024
By Jordan Whitehouse

An analog alarm clock sits atop of a dresser. The image is overlaid with hues of green. Photo: Abdülkadir Vardi, Unsplash

It’s no secret that the quality of our sleep declines as we age, but until recently there have been few large studies looking at the relationship between sleep in older adults and cognitive impairment.

About five years ago, a team of researchers from Concordia, the Université de Montréal and McGill University took a deep dive into data from the more than 26,000 participants of the Canadian Longitudinal Study on Aging to better decipher if lack of sleep played a role in memory decline.

They specifically looked at three groups: people sleeping normally, chronic insomniacs and people with symptoms of insomnia but not reporting problems with daytime functioning.

Their results, published in the journal SLEEP, show that chronic insomnia, in particular, has a significant impact on the memory of those aged 45 or older.

That chronic-insomnia distinction is an important one to make, says Nathan Cross, one of the co-leads of the study who was a postdoctoral fellow at Concordia’s Sleep, Cognition and Neuroimaging Lab at the time.

Headshot of a man with brown hair and short brown beard has a slight smile and is wearing a black polo shirt with white buttons. Nathan Cross

“Insomnia is a sleep disorder, but it’s primarily a psychological disorder where you’re perceiving that your sleep has a negative impact on you in the daytime,” he says. “And we found that it was only in those with the daytime complaint who had the deficiency in memory performance.”

Cross was also part of a follow-up study published in SLEEP showing that those whose sleep quality worsened between 2019 and 2022 were also more likely to experience memory decline.

Although these studies don’t prove that bad sleep is among the causes of dementia, they do show a direct link between chronic insomnia and memory loss, which can lead to conditions such as Alzheimer’s disease. They also add to a growing body of research that suggests that insomnia is associated with a significant risk of dementia.

Cross, now a research fellow at the University of Sydney, Australia, says that there is a lot more to unpack with the sleep-dementia link. And he believes that new improvements in technology will help make that happen.

“A lot of the blood-based biomarkers are much better at predicting who’s at risk for cognitive decline, and I think the link between those and sleep is going to be really important,” he says. “Even tools like MRI are constantly improving, and I think we’ll soon understand more about the brain-structure changes related to sleep.”

Read our related cover feature “Mind Matters: As dementia cases rise, new brain research offers hope through early detection”.

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