The new report, using data from the long-running Framingham Heart Study, shows that dementia rates have decreased by 44 per cent since the late 1970s and early 1980s, with nearly all of that drop among high school graduates.
"There was a trend there" for Alzheimer's, said Dean Hartley, director of science initiatives with the Alzheimer's Association. It shows "there may be modifiable lifestyles that may lower your risk for Alzheimer's."
So many people are entering the age when dementia becomes a threat and life expectancy is increasing so rapidly, the decline in rates of dementia will not translate to an overall drop in the number of dementia cases, cautioned senior author Dr. Sudha Seshadri, a professor of neurology at the Boston University School of Medicine.
The Framingham study is based in a predominately-white Massachusetts town west of Boston where thousands of residents have been closely followed by doctors since 1948. The new analysis, reported in the New England Journal of Medicine, looked at dementia rates in four 5-year blocks and used data from 5,205 individuals.
Those declines translate to reductions of 22 per cent, 38 per cent and 44 per cent in the second, third and fourth period, respectively, compared to the rate in the early years.
More education and brain power?
The researchers said some of the drop may be due to declines in rates of stroke, heart failure and atrial fibrillation, as well as better treatments for those conditions, "but none of these trends completely explain the decrease in the incidence of dementia."
Dr. Paul Schulz, a dementia neurologist at the University of Texas Health Science Center in Houston, who was not connected to the research, pointed out that "there's a lot of healthcare access issues related to education (and graduates) may have better insurance to see their doctor more often," which might have affected the results.
Dementia also tended to show up later in life as time went on, the study found. The average age of diagnosis was 80 during the late 1970s and 85 in the most recent group.
"Rising educational levels might have contributed to the 5-year delay we observed in the mean age at onset of clinical dementia," the researchers said.
Hartley said it's important to fund more research to see what lifestyle changes might lower the risk further. "A number of things people to do to stay healthy" such as exercise, a better diet and social stimulation "could protect their brain," he said