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More than 55 million people worldwide have dementia, a number that’s expected to nearly triple by 2050. But addressing 14 risk factors over the course of one’s life — starting in childhood — could prevent or delay nearly half of cases, according to a large report by 27 dementia experts.
Based on reviews of the latest evidence, the Wednesday report by The Lancet Commission on dementia prevention, intervention and care adds two risk factors — high cholesterol and vision loss — to 12 others previously identified in its 2020 report. Those existing risk factors are less education, head injury, physical inactivity, smoking, excessive alcohol consumption, hypertension, obesity, diabetes, hearing loss, depression, air pollution and infrequent social contact.
The research team wanted to compile and “add to evidence to give individuals and government accessible, reliable information and to help set a research agenda by highlighting what we don’t know,” said the report’s lead author Dr. Gill Livingston via email. “The progress in preventing and treating dementia is accelerating.”
The initial 12 risk factors were linked with 40% of cases, but the new report suggests addressing the 14 risk factors could help eliminate or delay 45% of dementia cases, said Livingston, a professor of psychiatry of older people at University College London.
High cholesterol in midlife from around age 40 was linked with 7% of dementia cases, and untreated vision loss in late life was associated with 2% of cases.
The risk factors associated with the greatest proportion of people developing dementia worldwide were high cholesterol, hearing impairment, less education in early life and social isolation in later life, the authors found.
This “critical” update calls attention to two risk factors that preventive neurologist Dr. Richard Issacson says his clinical practice has been evaluating for over a decade. “Now the evidence has caught up to what we recommend to patients,” said Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida, who wasn’t involved in the new study.
Influencing brain function
The report doesn’t establish with certainly that these risk factors directly cause dementia, experts said. It’s also possible that some risk factors may be early signs of a dementia diagnosis yet to come, meaning eliminating those factors may not always reduce risk of developing the disease, said Dr. Klaus Ebmeier, Foundation Chair of Old Age Psychiatry at the University of Oxford, in a news release. Ebmeier wasn’t involved in the study.
But other research has provided theories on the link between these vulnerabilities and dementia risk.
The link between excess body fat and dementia, for one, may be due to the involvement of body fat in metabolic and vascular processes associated with the buildup of beta-amyloid protein, a hallmark sign of Alzheimer’s disease.
Exercise may help keep dementia at bay by increasing levels of a protein known to strengthen communication between brain cells, according to a January 2022 study. Exercise can also reduce inflammation, which kills nerve cells. And being socially engaged can help someone reduce stress and better access health care.
Education is also vital for several reasons. “Most importantly it makes the brain more resilient to damage, so people can have changes but still function well,” Livingston said. “It also helps people make good choices by enabling them to think about evidence in a more educated way, and it is related to getting better jobs, and money gives more choices, for example, in health care and where to live.”
The full mechanisms of these risk factors need to be further investigated, said American Academy of Neurology fellow Dr. Glen R. Finney, who wasn’t involved in the study.
Explanations for the findings could boil down to a “combination of promoting the physical development and health of the brain, preventing damage to the brain, and enhancing and maintaining stimulation of the brain, which in and of itself aids brain health and function,” added Finney, director of the Geisinger Memory and Cognition Program in Wilkes Barre, Pennsylvania.
That may explain the increased risk potentially imparted by vision or hearing loss and air pollution.
How well a person can hear or see influences their ability to engage with their surroundings, have meaningful interactions with other people and be physically active, all of which are sensory inputs that stimulate the brain and build up its cognitive reserve, Isaacson said.
“If you don’t use it, you lose it,” he said, adding that giving patients hearing aids or glasses often provides them with a new lease on life.
Researchers are still trying to understand what components of air pollution may be responsible for the connection to dementia risk, but particles have been found in the buildup of amyloid plaques in the brains of people with Alzheimer’s, Isaacson said. Living near a highway has also been associated with a higher risk of dementia.
A call to action
Many of these risk factors can be addressed by individuals on their own, said Dr. Susan Kohlhaas, executive director of research at Alzheimer’s Research UK, in a news release.
“But others, like air pollution and early childhood education, are bigger than individuals and communities,” said Kohlhaas, who wasn’t involved in the study. “Tackling them will need structural changes to society to give everyone the best chance of a healthy life, free from the impact of dementia. Public health leaders must not ignore this message.”
Based on the risk factors, the authors also recommended 13 policy and lifestyle changes to help prevent or better manage dementia.
Policy guidance for government agencies includes ensuring quality education is available to all and providing information about the risks of cigarette smoking and excessive alcohol consumption and how to stop, as well as controlling prices and preventing smoking in public places.
Individuals should engage in cognitively stimulating activities, use head protection in contact sports or while riding bikes, and exercise regularly.
Maintaining a healthy weight and treating obesity as early as possible also helps prevent diabetes risk. The authors also recommended people maintain a systolic blood pressure of 130 mmHg — millimeters of mercury — or less beginning at age 40.
Treatment for depression, hearing loss, vision loss and high cholesterol is also important.
If you can’t move to an area with less air pollution, what you can do is use HEPA filters in your house and avoid using wood- or coal-burning ovens or heating, experts said.
The health and social impact of dementia worldwide has been estimated to cost over $1 trillion per year. But implementing some of these guidelines could save England, for example, around €4.2 billion, according to a modeling study published alongside the report.
“Even in the cases of dementia these steps don’t prevent, quality of life is better for people … who have had these risks addressed,” Finney said via email. “And the dementia specific medications like the acetylcholinesterase inhibitors and memantine can help and should be used. We have to fight neurologic nihilism — we can protect and help the brain and should!”
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