Lack of good quality sleep has long been associated with an increased risk of developing dementia, but recent research goes further: providing us with an optimal amount of nighttime sleep to minimize the risk of dementia later in life.
Using pooled data from 69 previous studies, a team from York University in Canada conducted a statistical analysis to look for associations with dementia for three factors: physical activity, time spent sitting, and sleep duration.
These are all variables that we can control, to a point, and the numbers have shown that 7-8 hours of sleep each night is the sweet spot for minimizing dementia risk.
Additionally, researchers found that prolonged sitting (more than 8 hours per day) and lack of physical activity (less than 150 minutes per week) were also linked to a significant increase in the chances of developing dementia.
“Regular physical activity, less sedentary time, and adequate nighttime sleep (7 to 8 hours) may be associated with reduced risk of dementia and are potentially modifiable factors in preventing or delaying dementia,” the researchers write in their published article.
Sleeping less than 7 hours per night was linked to an 18 percent increase in dementia risk, while staying more than 8 hours per night was correlated with a 28 percent increase.
These results are consistent with previous studies: too much sleep can be as harmful to our health as too little sleep.
If you want to aim for a goal, a time frame of between 7 and 8 hours seems best.
The researchers stress, however, that their review does not prove cause and effect – these are associations, not direct links.
Plus, it can be tricky to distinguish between triggers and consequences: Research suggests that sleeping too much is a sign that Alzheimer’s has already started, for example, and not just a driver of the disease.
Add to that the link to physical activity and recommendations around excessive sitting – both previously linked to brain health issues – and it appears we have a set of brain-healthy behaviors.
Although the researchers haven’t done any testing themselves, they point to the benefits of exercise, regular movement, and sleep for maintaining active blood flow in the brain, removing waste from neurons, and protecting other brain-related parts of the body (like the heart).
With no cure yet available and the number of cases of dementia expected to continue to rise in the coming years, experts want to study ways that people can limit their risk of developing diseases such as Alzheimer’s.
It is estimated that about half of all cases could be prevented by addressing lifestyle risk factors.
“Overall, a healthy movement behavior profile may promote vascular, neurotrophic, and anti-inflammatory effects that collectively support brain health and may delay the onset or progression of dementia,” the researchers write.
One advantage of the research is the large number of people included: almost 4.5 million in total.
It’s also worth noting that the data covers people aged under 35, a much younger starting point than in many other dementia studies.
All studies reviewed followed participants from a dementia-free starting point and then assessed the incidence of dementia over time.
However, there are also limitations.
The studies reviewed varied widely in terms of data collection and compilation, and there were more numbers on some behaviors than others – only 3 of the 69 studies looked specifically at sedentary habits, for example.
Gathering more data on the link between dementia risk and spending too much time sitting could be an avenue for future studies, the researchers suggest.
Related: Simple blood test can predict dementia risk in women decades before symptoms appear
“Future studies in middle-aged adults and longer-term follow-up, including changes in movement behaviors over time, are needed to better understand the relationship between physical activity, sedentary behavior, and sleep for dementia risk,” the researchers write.
The research was published in PLOS One.
This article was fact-checked by Michelle Starr and edited by Rebecca Dyer. Although we are proud of our process, we are only human. If you spot an error, please let us know.
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