Dementia plummets by nearly one-third among U.S. seniors, RAND says

Nov. 7 (UPI) -- The prevalence of dementia in the United States is declining among people over age 65, falling dramatically from 2000 to 2016, a RAND Corp. study says.

Nationwide, the age-adjusted prevalence of dementia fell to 8.5% of people over age 65 in 2016, down by nearly one-third from 12.2% of people over age 65 in 2000, according to the researchers.

Females are more likely to live with dementia, but the sex difference has narrowed, the study found.

Among men, the prevalence of dementia fell by 3.2 percentage points, from 10.2% to 7.0% over the 16-year span. The decrease was larger among women, down 3.9 percentage points, from 13.6% to 9.7%.

Differences in the prevalence of dementia between Black men and White men also narrowed, the investigators said.

Among non-Hispanic White men, the prevalence of dementia decreased from 9.3% to 6.6%, while among non-Hispanic Black men the rate fell from 17.2% to 9.9%.

Péter Hudomiet, the study's lead author, said that while the reasons for the decline in the prevalence of dementia are not certain, the trend is good news for older Americans.

He told UPI that the researchers expected a general decline in dementia prevalence, similar to several recent publications from the United States and Europe.

"We were less sure about how inequalities in dementia changed recently," he said.

Hudomiet, an economist at RAND, a nonprofit research organization based in California, told UPI in an email: "These favorable findings were somewhat surprising because health inequalities were reported to have increased in recent decades. ... Fortunately, unlike in mortality, we see a narrowing gap in dementia."

The study was published Monday in the journal Proceedings of the National Academy of Sciences.

According to RAND, an estimated 6.2 million U.S. adults aged 65 or older had dementia in 2021. Age is the strongest risk factor for dementia, so increasing life expectancies are expected to substantially increase the prevalence of Alzheimer's disease and related dementias -- from about 50 million to 150 million affected people worldwide by 2050.

But the researchers cited "growing evidence" that age-adjusted dementia prevalence has been declining in developed countries, possibly due to rising levels of education, a reduction in smoking and better treatment of key cardiovascular risk factors such as high blood pressure.

Hudomiet said it's also possible that, given numerous studies being released on steps to take to avoid dementia, some of the decline may be attributed to people heeding such advice.

"It is also plausible that other behavior factors, such as smoking [cessation], cognitive activities, social activities, etc., played a role," he said.

The researchers found a narrowing sex gap in dementia since 2000, "which occurred at the same time when the labor force participation rate rapidly increased among women," he added.

The RAND modeling looked at cognitive status based on a broad set of cognitive measures from 21,000-plus people from the nationally representative Health and Retirement Study, which has been ongoing for more than two decades.

Researchers said the model can produce accurate estimates of dementia prevalence by age, sex, education, race and ethnicity, and by a measure of lifetime earnings.

Higher education contributed, in a statistical sense, to about 40% of the reduction in dementia prevalence among men and 20% of the reduction among women, RAND said, while "changes in the older population by age, race and ethnicity, and cardiovascular risk factors mattered less."

Yet, various demographic groups are closing the education divide, RAND noted.

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

The RAND study was funded by the National Institute on Aging, a part of the National Institutes of Health.