‘Good news for older Americans’: Dementia prevalence is declining

Dementia prevalence dropped 3.7 percentage points in the U.S. from 2000 to 2016, according to a RAND Corporation study published in Proceedings of the National Academy of Sciences.

“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,” Péter Hudomiet, PhD, MA, MSc, the study’s lead author and an economist at RAND, said in a press release. “This decline may help reduce the expected strain on families, nursing homes and other support systems as the American population ages.”

Hudomiet and colleagues examined data from the Health and Retirement Study (HRS), a nationally representative survey. Their analysis included information on 21,442 participants aged 65 years and older.

The survey included “a range of cognitive tests,” according to the researchers, and some participants underwent dementia clinical assessment. Hudomiet and colleagues then developed a longitudinal, latent-variable model of cognitive status, which “provides more accurate estimates of dementia prevalence in population subgroups than do previously used methods on the HRS.”

From 2000 to 2016, the age-adjusted prevalence of dementia decreased from 12.2% (95% CI, 11.7 to 12.7%) to 8.5% (7.9 to 9.1%) — “a statistically significant decline of 3.7 percentage points or 30.1%.”

Notably, dementia prevalence was higher for women than men over the entire period, “but the difference shrank between 2000 and 2016.” For men, dementia prevalence decreased by 3.2 percentage points from 10.2% to 7%. The decrease was greater for women, though, at 3.9 percentage points, from 13.6% to 9.7%.

“Females are more likely to live with dementia, but the sex difference has narrowed,” the researchers wrote. “In the male subsample, we found a reduction in inequalities across education, earnings, and racial and ethnic groups; among females, those inequalities also declined, but less strongly.”

They also noted substantial increases in the level of education between 2000 and 2016 in the sample, and that “education is a very strong predictor of dementia.”

“This compositional change can explain, in a statistical sense, about 40% of the reduction in dementia prevalence among men and 20% among women, whereas compositional changes in the older population by age, race and ethnicity, and cardiovascular risk factors mattered less,” they wrote.

Hudomiet and colleagues said they “found notable differences in the evolution of dementia by race and ethnicity.” Dementia prevalence was higher in people from underrepresented racial and ethnic populations, in both men and women.

The difference in prevalence between Black and white people “remained stable among women,” but narrowed among men. For white men, dementia prevalence decreased from 9.3% to 6.6% — a drop of 2.7 percentage points, or 29%.

For Black men, though, the rate fell from 17.2% to 9.9% — a drop of 7.3 percentage points, or 42.6%.

“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 in the release.

In all, the researchers wrote that “the gap in dementia prevalence narrowed between men and women, and inequalities decreased between education, income, and race and ethnicity groups, especially among men.”

“Despite these favorable trends, we still find substantial dementia inequalities across subpopulations; women, racial and ethnic minority groups, and those with lower education face substantially higher chances of living with dementia,” they concluded. “While more research is needed to establish the causal mechanisms, our improved estimates of dementia prevalence and trends for population subgroups provide important information to public policy for quantifying the distributional burden of dementia and the associated long-term care needs.”

References:

Dementia prevalence is declining among older Americans, study finds. https://www.rand.org/news/press/2022/11/07.html. Published Nov. 7, 2022. Accessed Nov. 22, 2022.

Hudomiet P, et al. PNAS. 2022;doi:10.1073/pnas.2212205119.