Time to get your eyes checked: Vision loss among growing list of risk factors for dementia, study says
New report identifies 14 risk factors for dementia, and what can be done to prevent them
Two new risk factors for dementia — vision loss and high cholesterol — have been identified in a sweeping new report in a leading medical journal.
The 2024 Lancet Commission on dementia lists 14 risk factors for dementia, many of which can be influenced by lifestyle changes. Among them, untreated vision loss and high cholesterol stand out as new targets for preventative treatment alongside well-known health threats such as head injuries, smoking, excessive alcohol consumption and air pollution.
As Canada's senior population rises, so too does the prevalence of dementia. The Alzheimer Society of Canada estimates one million Canadians will be living with dementia by 2030.
Dementia is a term used to describe symptoms of cognitive decline including loss of memory, thinking and personality. Alzheimer's disease is the most common cause of dementia.
While aging is inevitable, late-life cognitive decline may not be. The Lancet Commission has reported that reductions in modifiable risk factors have the potential to prevent nearly half of dementia cases.
Dr. Gill Livingston, a professor of psychiatry of older people at University College London who is the commission's lead author, said she hopes to decrease the period of deterioration at the end of life.
"If you ask people who are age 50 and over what illness they fear, and most, a majority of them will say dementia," she said.
Vision loss in old age affects more than just the ability to see
The commission looked at multiple studies and meta-analyses with data from a combined total of several million participants and found "considerable evidence" supporting vision loss as a risk factor for dementia.
Hearing loss had previously been listed as a risk factor, as losing that sense decreases brain stimulation. The same thing happens when you lose your sight — when you can't see, it's hard for you to interpret and interact with the world.
One meta-analysis cited by the Lancet team found cataracts and retina damage caused by diabetes had the strongest associations with dementia.
Another study found that treating cataracts may decrease the risk of dementia. While people with cataracts had an increased risk of dementia, those with treated cataracts had no greater risk than people with healthy lenses.
Though the idea of cataract surgery can be unnerving to some, Dr. Peter Kertes, ophthalmologist-in-chief at the Kensington Eye Institute and professor and chair of the University of Toronto's ophthalmology department, said that there are options available to make the process accessible even to those currently experiencing dementia.
"We find not infrequently that patients who are cognitively impaired who have significant cataracts," he said. "After their cataract surgery, their cognitive impairment improves considerably and their life improves considerably."
Health habits at mid-life inform dementia risk later in life
Several of the risk factors identified in the report were age-specific. While treating vision loss in late life decreased risk of dementia, mid-life was identified as a key time for treating and moderating cholesterol levels.
Cholesterol is a wax-like steroid that is present in blood. It has many essential functions, including building other steroids and vitamin D.
Lipoproteins carry cholesterol through the body, and one form — known as low-density lipoproteins (LDL) — can stick to the walls of blood vessels, sometimes creating blockages.
High levels of LDL cholesterol — otherwise known as the "bad" cholesterol — are primarily caused by consuming foods containing high levels of saturated fats.
Excess cholesterol in the brain is associated with an increased risk of stroke, as well as buildup of harmful proteins associated with dementia.
Many risk factors for dementia, including cholesterol levels, interact with each other, said Livingston.
"The person who is less physically active is more likely to have high blood pressure and more likely to be overweight and more likely to have diabetes, so they cluster together," she said.
'Use it or lose it'
When it comes to staying mentally sharp, it's important to keep your brain active by participating in activities that challenge your brain's memory, attention and decision making.
Dr. Anthony Levinson, the John Evans chair in health sciences educational research at McMaster University, said that people are generally aware of the importance of staying cognitively active.
"There are people who do try to stay engaged, or they're doing puzzles more, or they're learning a new language," he said.
Other activities that boost and maintain brain function include reading, writing, playing musical instruments and participating in conversations.
The Lancet team noted that dementia prevention starts as early as childhood education.
However, new evidence has shown that midlife cognitive activity, even in people who received little education, can be preventative as well.
While cognitively stimulating hobbies can help with dementia reduction, the best thing you can do is have a job that is mentally challenging because you spend more time at your job than doing hobbies, the Lancet report found.
The report found that high cognitive stimulation increases your "cognitive reserve" — the ability to continue functioning normally despite unseen changes in your brain.
Making the change
Decreasing the risk of dementia starts with changing people's perception of late-life cognitive decline, said Levinson.
"People have misconceptions that if you live long enough, everybody's going to get dementia," he said. "Those are not true."
About one in four seniors aged 85 or older have been diagnosed with dementia, according to the Canadian Institute for Health Information.
Not every dementia prevention technique requires a significant lifestyle change. While some changes, such as diet and exercise, can be more difficult to make, actions as simple as getting your hearing checked make a difference, said Levinson.
Dr. Samir Sinha, director of geriatrics at Mount Sinai and the University Health Network Hospitals in Toronto, said systemic changes in public health are also needed.
Primary care providers are key to managing a healthy lifestyle. Yet one in five Canadians don't have access to regular primary care providers, such as a family doctor or nurse practitioner.
"We need to make sure that every Canadian has access to a primary care provider, that we have the right mix of specialists, including geriatricians, to really help manage the care of older people, and also to prevent things like dementia as well," said Sinha.
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