How Much Sleep And Exercise Actually Reduces Dementia Risk?

Though people with dementia tend to face sleep disruptions, it’s a bit of a “chicken and egg” link: “Does poor sleep increase dementia risk, or does dementia lead to poor sleep?” Alzheimer’s Society said.

“Some researchers believe that both of these theories could be true, and the relationship could be circular.”

Whatever the direction of the link, though, one paper found that those who got fewer than six hours of sleep in midlife were less likely to develop dementia.

And a new paper published in PLOS One, which involved data from dozens of other studies, says there may be a “sweet spot” for reducing dementia risk.

The data the researchers used came from millions of people aged 35 and over across decades of research. It looked at day-to-day habits, like rest and movement, and compared those to the rate of dementia among participants.

Parmis Mirzadeh, who helped to write the study, said these studies “provided an opportunity to better understand how daily habits like physical activity, sedentary time and sleep collectively shape brain health over time”.

They found that seven to eight hours’ sleep was linked to a lower dementia risk, while both more and less sleep were associated with an increased likelihood of developing the condition.

The longer sleep pattern (regularly getting more than eight hours’ sleep) was most associated with higher dementia risk.

Previous research has shown that people who sleep more than nine hours a night are more likely to develop dementia 10 years later.

Yes. These researchers also looked at how physical activity and sedentary behaviours seemed to be linked to people’s dementia risk.

They found that people who stuck to the recommended 150 minutes of physical activity a week were 25% less likely to face dementia.

“One of the more surprising findings was how sparse the data remains for sedentary behaviour, despite it being recognised as a distinct health risk for more than a decade,” Mirzadeh stated.

Nonetheless, researchers think sitting for more than eight hours a day may increase dementia risk.

“We hope this work helps raise awareness that everyday behaviours such as physical activity, sedentary time and sleep are associated with brain health,” Mirzadeh added. “Because these are modifiable, they represent practical targets for interventions aimed at reducing dementia risk at the population level.”

It’s worth noting, however, that this paper only looked at associations and did not prove a causal link.