Dementia May Be on the Decline

A new study from RAND credits several possible factors. Another recent study suggests nutrition may also play a role.

By Linda Hildebrand 

A study funded by the National Institute on Aging found the memory disease fell by about 3.7 percentage points between 2000 to 2016 – a drop from about 12 in 100 seniors to 8.5 in 100 seniors during those 16 years.

“The reasons for the decline in the prevalence of dementia are not certain, but this trend is good news for older Americans and the systems that support them,” said economist Peter Hudomiet, the study’s lead author with Michael D Hurd and Susan Rohwedder of the RAND Center for the Study of Aging.

That means savings in associated costs, such as nursing care, for families, insurers and government, he said.

Meanwhile, Columbia University in early November in the journal Neurology published findings of a study that showed memory declined over 20 years at a slower rate among older adults on food stamps than among eligible people who opt out of the federal food aid.

The rate of decline in the RAND study was most rapid between 2000 and 2004. Dementia was more prevalent in women than in men over the entire period, but the degree of difference shrank.

Dementia affects about 6.2 million adults 65 or older in America, according to RAND. RAND tackled prevalence within the population, because increasing population and lifespans inevitably grow numbers.

RAND’s study credits the trends to possible factors including better education, less smoking and better cardiovascular care, such early treatment of high blood-pressure. The Columbia study suggests nutrition may have a role, too.

The RAND findings are published in the Nov. 7 edition of the journal Proceedings of the National Academy of Science.

The RAND trends

RAND’s ongoing study employs a novel model.

It assesses a broad set of cognitive measures elicited from more than 21,000 people who participate in the national Health and Retirement Study, a population-representative survey that has been fielded for more than two decades.

The model isolates dementia using the longitudinal dimension of the data. Its structure ensures the dementia classification is calibrated within population subgroups and, therefore, is equipped to produce accurate estimates of dementia prevalence by age, gender, education, race and ethnicity, and by a measure of lifetime earnings.

For example, education stands out statistically as a contributing factor to reducing dementia. It accounts for about 40% of the reduction among men and 20% for women, Hudomiet said.

The number of college-educated participants over age 65 has expanded across demographic groups, which may show more relevant differentiations in the future. The reason is because access to higher education became more accessible to women and to non-White people through the 20th century so is gaining equity among people who are now older than 65.

“Closing the education gap across racial and ethnic groups may be a powerful tool to reduce some health inequalities and dementia differences in particular, an important public health policy goal,” Hudomiet said.

Among men, the prevalence of dementia decreased by 3.2 percentage points from 10.2% to 7.0%. The decrease among women was 3.9 percentage points from 13.6% to 9.7%.

Differences in the prevalence of dementia between Black men and White men of non-Hispanic ethnicity narrowed between 2000 and 2016, with the prevalence of dementia dropping by 7.3 percentage points among Black men as compared to 2.7 percentage points among White men.

The age-adjusted prevalence of dementia tended to be higher among racial and ethnic minority men and women.

RAND Corp., a nonprofit research organization that Douglas Aircraft Co. created in 1948 to conduct U.S. Air Force research, titled its study “Trends in Inequalities in the Prevalence of Dementia in the U.S.”


Federal food assistance known as food stamps is actually SNAP, the Supplemental Nutrition Assistance Program.

Columbia University’s Mailman School of Public Health for two decades compared dementia progress among3,555 low-income Americans who qualified for the federal vouchers to pay for groceries. Only 559 of them received the SNAP benefits.

Researchers measured memory function every two years for 20 years. People were asked to complete memory and thinking tests, such as recalling a list of words and answering questions about what they can remember in their everyday lives.

The group of 559 SNAP recipients showed about two fewer years of cognitive aging over a 10-year period compared with the 2,996 who didn’t take SNAP benefits.

“With the number of people with Alzheimer’s disease and other dementias expected to increase, this low participation is a huge, missed opportunity for dementia prevention,” said senior author Adina Zeki Al Hazzouri, assistant professor of epidemiology at the Mailman School.

Outreach programs could reduce the stigma of SNAP and simplify the application process so more eligible older Americans will participate, she said.

At the beginning of the study, SNAP users had lower socioeconomic status and a greater number of chronic conditions than those who did not participate in the program, so researchers used techniques to account for those differences. After adjusting for the differences between the two groups, researchers found that while SNAP users had worse memory scores at the start of the study, they had slower rates of memory decline compared to those who didn’t use SNAP money to buy their groceries.

“Eating healthier may benefit brain health,” said study first author Peiyi Lu, a postdoctoral research scientist in epidemiology at the Mailman School. “SNAP may also reduce stress and overall financial hardship, which has been linked to premature cognitive aging and reduced brain health.”

As of press time, Columbia University Mailman School of Public Health did not provide information requested about how the study may have tracked the nutrition that SNAP and non-SNAP low-income participants consumed.

The study is online in the Neurology journal of the American Academy of Neurology.

Linda Hildebrand is a longtime newspaper editor and consumer-action reporter.



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