12 risk factors key to preventing nearly half of dementia cases, report says

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Ken Walker is living through the early stages of dementia, but he's not staying silent about it. (From January 2020) – Jan 6, 2020

Up to 40 per cent of the world’s dementia cases are linked to a handful of risk factors – and tackling these could prevent or delay the onset of this debilitating condition, a new report has found.

The report, the second by the Lancet Commission on Dementia Prevention, Intervention and Care, found that just a dozen risk factors account for a huge percentage of dementia cases. The authors reviewed existing research on dementia and came up with recommendations to reduce and delay cases worldwide.

“This article is pointing out that there’s a huge potential to make an impact on the numbers, the costs and the occurrence in society,” said Dr. Howard Chertkow, scientific director of the Canadian Consortium on Neurodegeneration in Aging and senior scientist at Baycrest’s Rotman Research Institute.

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Around eight per cent of Canadians over 60 are at risk of developing dementia, he said, with the risk growing if they have a family history of the condition.

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“Every case of dementia is a tragedy not just for the person, but for their spouse, their kids,” he said.

The number of people with dementia, currently estimated at around 564,000, will double within the next 25 years, he said, at massive cost not just to the people involved, but to society.

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And, as there is no cure for Alzheimer’s disease, preventing Alzheimer’s and dementia is hugely important, he said.

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The risks outlined in the report are: low education, hearing loss, traumatic brain injury, hypertension, alcohol use, obesity, smoking, depression, social isolation, physical inactivity, air pollution and diabetes.

Broadly, these risks, and fixing them, fall into two categories, Chertkow said.

“There are things that are injurious to the brain, and then there are things that protect the brain, building what we call cognitive reserve.”

Things that injure the brain include hypertension or alcohol use, for example.

Things like education – more than just being an indicator of socioeconomic status – actually seem to change the brain, making it more resistant to decline, said study co-author Dr. Eric Larson, a senior investigator at Kaiser Permanente Washington Health Research Institute in Seattle.

“We know, for example, that if you look at the hand of a concert violinist and the corresponding part of their brain, the fact that they overuse that hand compared to everybody else leads to this really dense connection of neurons in the brain,” he said.

Education is thought to have a similar effect, by building up a “reserve” of connections that, even if someone declines later in life, will still help keep them above the line of dementia, Chertkow said.

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The authors recommend providing all children, male and female, with a primary and secondary school education. Around seven per cent of dementia cases are associated with education, they say.

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The other major risk factor, associated with around eight per cent of cases, is hearing loss, particularly in middle age, according to the report.

There are a number of theories as to how hearing and dementia risk are linked, Chertkow said.

“One is when people aren’t hearing well, they withdraw from social contacts. They stop seeing their friends, they stop going out.”

Highly social people appear to have less dementia, he said, so social withdrawal could have a negative effect.

There’s also likely a biological connection between hearing and memory, he said.

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“It’s been shown that in people with hearing loss, if you do MRI scans, parts of their brain get smaller. Their cortex gets thinner, the memory parts of the brain get smaller.”

Something as simple as routine hearing tests, and encouraging hearing aid use, could be effective strategies for lessening dementia risk down the road, he said.

All of the report’s recommendations could be implemented at any point in a person’s life, Larson said.

“A lot of the stuff on that list is common sense… It’s healthy living in general. So the question of, when should you do it, why not whenever?”

While things like quitting smoking and alcohol use are a bit more within an individual’s control, some of these interventions, like reducing air pollution and improving education, require government support. This is important to get, Larson said.

“I don’t know where it fits on the scale of most to least important. But I’d put it right up there with one of the top public health priorities.”

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