RAND Corporation: Study finds dementia rates among Americans aged 65 and older fell 3.7% from 2000 to 2016

A recent study conducted by the RAND Corporation found that the prevalence of dementia in the U.S. population aged 65 and older fell by 3.7 percentage points from 2000 to 2016. The age-adjusted prevalence of dementia fell from 12.2% of people aged 65 and older in 2000 to 8.5% of people aged 65 and older in 2016, a decrease of nearly one-third from the 2000 level. The prevalence of dementia continued to decline throughout the study period, with particularly rapid declines observed between 2000 and 2004.

The difference in dementia rates between black and white men narrowed, with the rate falling 7.3 percentage points for black men and 2.7 percentage points for white men. The findings were published recently in the Proceedings of the National Academy of Sciences.

“The reasons for the decline in dementia rates are uncertain, but the trend is good news for older Americans and the systems that support them,” said Petr Hudomeit, an economist at the nonprofit research organization RAND and the study’s lead author. “The decline may help reduce the expected strain on families, nursing homes, and other support systems as the U.S. population ages.”

Michael D. Hurd and Susan Rowe Weider of the RAND Corporation were co-authors of the study.

Women had higher rates of dementia than men throughout the period, but that difference similarly narrowed between 2000 and 2016. Among men, the prevalence of dementia fell by 3.2 percentage points, from 10.2% to 7.0%. The decline was even greater among women, from 13.6% to 9.7%, a drop of 3.9 percentage points.

In 2021, approximately 6.2 million U.S. adults aged 65 or older will have dementia. Because age is the strongest risk factor for dementia, it is predicted that increasing life expectancy will increase the global prevalence of Alzheimer's disease and related dementias from approximately 50 million to 150 million by 2050.

However, there is growing evidence that age-adjusted dementia prevalence has been falling in developed countries, possibly because of rising education levels, reduced smoking, and better treatment of key cardiovascular risk factors such as high blood pressure.

Any changes in these age-specific rates have important implications for predicted morbidity and associated costs, such as payments for care by households, insurers, and governments.

The new RAND study uses a novel model to assess cognitive status based on a broad set of cognitive measures obtained from more than 21,000 people participating in the National Health and Retirement Study, a large, population-representative survey that has been conducted for more than 20 years.

The model improves the precision of dementia classification by exploiting the longitudinal dimension of the data. Importantly for the study of inequality, the model was constructed to ensure that dementia classification is calibrated across population subgroups and therefore has the power to produce accurate estimates of dementia prevalence by age, sex, education, race and ethnicity, and by lifetime income.

The RAND study found that education was a significant factor that contributed to the reduction in dementia in a statistically significant way, explaining about 40% of the reduction in dementia prevalence among men and 20% among women.

The percentage of college-educated men in the study increased from 21.5% in 2000 to 33.7% in 2016, while the percentage of college-educated women increased from 12.3% to 23% during that period.

Trends in education levels differ across demographic groups, which could affect future dementia inequalities. For example, while women have traditionally had lower education levels than men, women are becoming more educated among younger generations. And while racial and ethnic minority groups still have lower education levels than non-Hispanic whites, the gaps across racial and ethnic groups have narrowed.

"Narrowing educational gaps between racial and ethnic groups may be a powerful tool to reduce health inequities in general and dementia in particular, which is an important public health policy goal," Hudomit said.

Age-adjusted prevalence of dementia tended to be higher among racial and ethnic minority individuals and was true for both men and women. However, among men, the difference in prevalence between non-Hispanic black and white individuals narrowed, while it remained stable among women. Among non-Hispanic white men, the prevalence of dementia decreased from 9.3% to 6.6%. Among non-Hispanic black men, the rate decreased from 17.2% to 9.9%.

From cnBeta