In the absence of an effective drug treatment for dementia, researchers are emphasizing the importance of addressing modifiable risk factors linked to the disease, one of which was newly identified in a recent study published in JAMA Neurology, Paula Span reports for the New York Times.
'A drastic change in concept' for dementia treatment
As experimental drugs continue to prove ineffective against rising cases of dementia, many public health experts and researchers have shifted their focus to addressing known risk factors, including untreated high blood pressure, hearing loss, and smoking.
"It would be great if we had drugs that worked," said 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."
According to Julio Rojas, a neurologist at the University of California-San Francisco, shifting the primary focus to treating modifiable risk factors marks "a drastic change in concept."
By focusing on behavioral changes and interventions that are widely available and can be supported with strong evidence, "we are changing how we understand the way dementia develops," Rojas said.
Could addressing vision health reduce the likelihood of dementia?
For the study, researchers analyzed vision health in the United States using data from the Health and Retirement Study. Overall, the researchers estimated that roughly 62% of current dementia cases could have been prevented across all risk factors. In addition, they estimated that 1.8%—or around 100,000 cases—could have been prevented with healthy vision.
"A massive change could be made in the number of people with dementia," said Livingston. "Even small percentages—because so many people have dementia and it's so expensive—can make a huge difference to individuals and families, and to the economy."
While 1.8% is a relatively small percentage, Joshua Ehrlich, an ophthalmologist and population health researcher at the University of Michigan and the study's lead author noted that the figure represents a comparatively easy solution since eye exams, eyeglass prescriptions, and cataract surgery are less expensive and more accessible than many other interventions.
"Globally, 80 to 90 percent of vision impairment and blindness is avoidable through early detection and treatment, or has yet to be addressed," Ehrlich noted.
According to Rojas, who co-authored an accompanying editorial in JAMA Neurology, "[a] neural system maintains its function through stimulation from sensory organs." Without that stimulation, "there will be a dying out of neurons, a rearrangement of the brain," which can ultimately contribute to cognitive decline.
In addition, hearing and vision loss may affect cognition by limiting older adults' ability to participate in physical and social activities. "You can't see the cards, so you stop playing with friends," Ehrlich said, "or you stop reading."
While the link between dementia and hearing loss—cited as the most important modifiable risk by the Lancet Commission—is well established, there is not as much clinical data on the link between dementia and poor vision. But Ehrlich said he hopes the commission will add vision impairment to its list of modifiable risks when it updates its report.
Addressing modifiable risk factors
Still, reducing modifiable risk factors for dementia could have a significant impact on case numbers. Notably, CDC has incorporated this strategy into its National Plan to Address Alzheimer's Disease.
"A focus on these factors could also help reassure older Americans and their families. 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," Span writes.
"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."
A delayed onset can even have a notable impact. "If, instead of getting it at 80, you get it at 90, that's a huge thing," she added.
To identify and address these modifiable risk factors, experts recommend taking steps several steps, including regular eye and hearing exams, exercise, weight control, smoking cessation, blood pressure medications, and diabetes care.
"[W]e'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." (Span, New York Times, 7/3)