The American population is getting older, but the percentage of U.S. seniors with dementia is actually declining, a new study found.
In the study, the researchers analyzed information from a nationally representative sample of about 21,000 U.S. adults ages 65 and older who were tested for dementia from 2000 to 2012. (About 10,500 people were tested in 2000, and 10,500 were tested in 2012; about 4,000 of the participants were tested in both of those years.)
In 2000, 11.6 percent of older adults had dementia, but that number dropped to 8.8 percent by 2012, the researchers found.
Although some previous U.S. studies had suggested the prevalence of dementia in the U.S. was declining in recent years, those studies were not representative of the entire U.S. population, the researchers in the new study said.
The new findings "add to a growing body of evidence that this decline in dementia risk is a real phenomenon, and that the expected future growth in the burden of dementia may not be as extensive as once thought," Dr. Kenneth Langa, the lead author of the study and a professor at the University of Michigan's Institute for Social Research and School of Public Health, said in a statement.
Dementia is not a specific disease, but rather a group of symptoms, which can include problems with thinking and solving problems, as well as personality changes, according to the National Institutes of Health. [6 Big Mysteries of Alzheimer's Disease]
The risk of developing these symptoms has also been linked toother factors, like education, the new study suggested. Researchers found that the people in the study who had more years of education had a lower risk of dementia. Those with 16 years or more of education were about 70 percent less likely to have dementia, compared with those who had less than 12 years of education. During the study period, the average number of years of education among participants increased from 12 to 13 years.
More years of education may help protect against dementia in a number of ways, the researchers said. Spending more years in school may help the brain's "cognitive reserve," meaning the brain may be better able to compensate for abnormalities that occur in older age.
Having more years of education can also allow people to obtain more cognitively challenging jobs, which could also help protect the brain, the researchers said. And people who have more years of education may also be more likely to exercise and eat healthy, and less likely to smoke, which are all behaviors that are linked with better brain health.
Interestingly, the researchers noted that the drop in dementia prevalence occurred despite increases in the rates of certain conditions that can increase the risk of dementia: diabetes, high blood pressure and obesity. The researchers said they suspect that better treatment of cardiovascular disease and diabetes may have also contributed to the decline in dementia.
Still, more research is needed to identify all the factors contributing to the decline in dementia prevalence, the investigators said.
The researchers noted that, despite the decline seen in the study, dementia will still be a very important health issue in years to come.
"It does nothing to lessen the impact that each case has on patients and caregivers. This is still going to be a top-priority issue for families, and for health policy, now and in the coming decades," Langa said.
Original article on Live Science.