The percentage of older Americans reporting serious problems with memory and thinking has declined in recent years -- and higher education levels may be part of the reason, a new study finds.
Researchers found that between 2008 and 2017, the proportion of older U.S. adults reporting "serious cognitive problems" declined from just over 12% to 10%.
The reasons are unclear, but an increase in Americans' educational attainment over time seemed to account for part of the trend.
Many studies have linked higher education levels to a lower risk of impaired thinking and dementia, said lead researcher Esme Fuller-Thomson, director of the University of Toronto's Institute for Life Course and Aging.
One theory -- the "cognitive reserve" hypothesis -- is that people with more education are better able to withstand the pathological brain changes that mark the dementia process.
That is, they can function at a higher level, for longer, than their less-educated peers with the same brain changes.
Education can also be a marker of other things that matter in dementia risk.
People with more education may be less likely to smoke, more likely to exercise and have a healthy diet, and also to have fewer chronic health conditions and better access to health care.
A caveat is that the current study did not look at actual dementia diagnoses.
"We can't say this is a decline in dementia, per se," Fuller-Thomson said.
Instead, survey respondents were asked a yes/no question: "Because of a physical, mental or emotional condition, does this person have serious difficulty concentrating, remembering, or making decisions?"
But that, Fuller-Thomson said, gets at how people were functioning in their daily lives, so the decline in self-reported problems is good news.
It's unlikely, she noted, that people in 2017 were simply interpreting the question differently from those in earlier years.
The study is not the first to show positive trends in older Americans' brain health. Some have found a decline in dementia diagnoses in recent decades. The Framingham Heart Study, which followed families over three generations, found that dementia diagnoses declined 44% between 1977 and 2008.
Fuller-Thomson said the new findings are line with that research, and add more recent data.
Matthew Baumgart is vice president of health policy at the Alzheimer's Association. He agreed the findings align with some studies tracking dementia incidence over time.
But, Baumgart noted, those patterns are not universal. They have been seen in some high-income Western countries with high education levels.
And the prevalence of dementia -- the number of people living with the disease -- is still growing, because of the boom in the elderly population, in the United States and globally.
"Even with select studies pointing to a decrease in dementia incidence, the global Alzheimer's and dementia epidemic is growing," Baumgart said.
According to the Alzheimer's Association, more than 6 million Americans are living with Alzheimer's, the most common form of dementia. That number is projected to double to nearly 13 million by 2050.
The current findings are based on 10 years of data from an annual Census Bureau survey. In total, it involved 5.4 million Americans age 65 and older.
In 2008, 13.6% of women reported serious cognitive problems, a figure that declined to just under 11% by 2017. Meanwhile, men showed a smaller relative decline -- from 10.2% to 8.8%.
The survey did not collect information on lifestyle habits like smoking, which has declined in the United States over the years. It also lacked data on physical health conditions and several other factors that may sway dementia risk.
But changes in people's educational attainment appeared to explain part of the positive trend, Fuller-Thomson said.
She speculated that other broad changes -- like improvements in air quality and even the removal of lead from gasoline in the 1970s -- could be potential contributors, too.
Baumgart said researchers are working to learn more about the modifiable risk factors for dementia.
That includes a clinical trial, funded by the Alzheimer's Association, which is testing whether a combination of lifestyle measures can slow cognitive decline in older adults at increased risk.
Those measures include exercise, better control of high blood pressure and diabetes, and mentally stimulating activities.
For now, the group recommends all of those things for supporting brain health in general.
When it comes to the burden of dementia on society, the swelling prevalence figure matters most, Baumgart said.
But for individuals, Fuller-Thomson said the decline in cognitive problems is encouraging. If 10% of older Americans reported such issues, she noted, that means 90% did not.
"Most older adults are functioning at a high level, and continue to contribute to society and thrive," she said.
The findings were published recently in the Journal of Alzheimer's Disease.
The Alzheimer's Association has advice on supporting brain health.
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