Dementia cases are climbing along with an ageing world population, and yet another much-anticipated Alzheimer’s medication, crenezumab, has proved ineffective in clinical trials — the latest of many disappointments. Public health experts and researchers argue that it is past time to turn our attention to a different approach: focusing on eliminating a dozen or so known risk factors, like untreated high blood pressure, hearing loss and smoking, rather than on an exorbitantly priced, whizz-bang new drug.
“It would be great if we had drugs that worked,” said Dr Gill Livingston, a psychiatrist at University College London and chair of the Lancet Commission on Dementia Prevention, Intervention and Care. “But they’re not the only way forward.”
Emphasising modifiable risks — things we know how to change — represents “a drastic change in concept,” said Dr Julio Rojas, a neurologist at the University of California, San Francisco. By focusing on behaviours and interventions that are already widely available and for which there is strong evidence, “we are changing how we understand the way dementia develops”, he said.
The latest modifiable risk factor was identified in a study of vision impairment in the United States that was published recently in JAMA Neurology. Using data from the Health and Retirement Study, the researchers estimated that 62% of current dementia cases could have been prevented across risk factors and that 1.8% — about 100,000 cases — could have been prevented through healthy vision.
Though that’s a fairly small percentage, it represents a comparatively easy fix, said Dr Joshua Ehrlich, an ophthalmologist and population health researcher at the University of Michigan and the study’s lead author.
The Lancet Commission identified nine risk factors accounting for much of the world’s dementia: high blood pressure, lower education levels, impaired hearing, smoking, obesity, depression, physical inactivity, diabetes and low levels of social contact. In 2020, the commission added three: excessive alcohol consumption, traumatic brain injuries and air pollution
That’s because eye exams, eyeglass prescriptions and cataract surgery are relatively inexpensive and accessible interventions.
“Globally, 80 to 90 per cent of vision impairment and blindness is avoidable through early detection and treatment, or has yet to be addressed,” Ehrlich said.
The influential Lancet Commission began leading the modifiable-risk-factor movement in 2017. A panel of doctors, epidemiologists and public health experts reviewed and analysed hundreds of high-quality studies to identify nine risk factors accounting for much of the world’s dementia: high blood pressure, lower education levels, impaired hearing, smoking, obesity, depression, physical inactivity, diabetes and low levels of social contact.
In 2020, the commission added three: excessive alcohol consumption, traumatic brain injuries and air pollution. The commission calculated that 40 per cent of dementia cases worldwide could theoretically be prevented or delayed if those factors were eliminated.
Ehrlich hopes the Lancet Commission will add vision impairment to its list of modifiable risks when it updates its report, and Livingston said it would indeed be on the commission’s agenda.
Why would hearing and vision loss contribute to cognitive decline?
“A neural system maintains its function through stimulation from sensory organs,” explained Rojas, a coauthor of an accompanying editorial in JAMA Neurology. Without that stimulation, “there will be a dying out of neurons, a rearrangement of the brain”.
Hearing and vision loss could also affect cognition by limiting older adults’ participation in physical and social activity.
“You can’t see the cards, so you stop playing with friends,” Ehrlich said, “or you stop reading”.
The link between dementia and hearing loss, the single most important factor the Lancet Commission cited as a modifiable risk, has been well established. There is less clinical data on the connection to impaired vision, but Ehrlich is a coinvestigator of a study in southern India to see whether providing older adults with eyeglasses affects cognitive decline.
Of course, this approach to reducing dementia is “aspirational”, he acknowledged: “We’re not going to eliminate low education, obesity, all of these.”
Some efforts, like raising education levels and treating high blood pressure, should begin in youth or midlife. Others require big policy changes; it’s hard for an individual to control air pollution, for example. Altering habits and making lifestyle changes — like stopping smoking, reducing drinking and exercising regularly — are not simple.
Some important risks for dementia lie beyond our control: genetics and family history, and advancing age itself. Modifiable factors, however, are things we can act on
Even fairly routine medical practices, like measuring and monitoring high blood pressure and taking drugs to control it, can be difficult for low-income patients.
Moreover, older Americans will be likely to notice that routine vision and hearing care are two services that traditional Medicare does not cover.
It will pay for care related to diabetic retinopathy, glaucoma or age-related macular degeneration, and it covers cataract surgery. But for more common problems correctable with eyeglasses, “traditional Medicare is not going to help you out much,” said David Lipschutz, associate director of the nonprofit Centre for Medicare Advocacy. Nor will it cover most hearing aids or exams, which are much higher expenses.
Some important risks for dementia lie beyond our control: genetics and family history, and advancing age itself. Modifiable factors, however, are things we can act on.
“People have such fears of developing dementia, losing your memory, your personality, your independence,” Livingston said. “The idea that you can do a lot about it is powerful.”
Even delaying its onset can have a great effect.
“If instead of getting it at 80 you get it at 90, that’s a huge thing,” she said.
Eye and hearing exams, exercise, weight control, stopping smoking, blood pressure medications, diabetes care — “we’re not talking about expensive interventions or fancy surgery or seeing specialists who are hours away”, Ehrlich added. “These are things people can do in the communities where they live.” — This article originally appeared in The New York Times.