In 2021, about 6.2 million U.S. adults aged 65 or older lived with dementia.
Because age is the strongest risk factor for dementia, it has been predicted that increasing life expectancies will substantially increase the prevalence of Alzheimer’s disease and related dementias from about 50 million to 150 million worldwide by 2050.
But in a study from RAND Corporation, scientists found the prevalence of dementia in the U.S. is declining among people over age 65, dropping 3.7 percentage points from 2000 to 2016.
They found the prevalence of dementia declined from 12.2% of people over age 65 in 2000 to 8.5% of people over age 65 in 2016—a nearly one-third drop from the 2000 level.
The prevalence of dementia decreased over the entire period, but the rate of decline was more rapid between 2000 and 2004.
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.
In the study, the team found the prevalence of dementia was higher among women than men over the entire period, but the difference shrank between 2000 and 2016.
Among men, the prevalence of dementia decreased by 3.2 percentage points from 10.2% to 7.0%. The decrease was larger among women—3.9 percentage points from 13.6% to 9.7%.
Previous research has shown that there is growing evidence that age-adjusted dementia prevalence has been declining in developed countries, possibly because of rising levels of education, a reduction in smoking, and better treatment of key cardiovascular risk factors such as high blood pressure.
Any change in these age-specific rates has important implications for projected prevalence and associated costs, such as payments for nursing care by households, insurance companies, and the government.
The new study used a novel model to assess the cognitive status of more than 21,000 people who participate in the national Health and Retirement Study.
The team found that education was an important factor that contributed, in a statistical sense, to the reduction in dementia, explaining about 40% of the reduction in dementia prevalence among men and 20% of the reduction among women.
The fraction of college-educated men in the study increased from 21.5% in 2000 to 33.7% in 2016, and the fraction of college-educated women increased from 12.3% to 23% over this period.
Trends in the level of education differ across demographic groups, which may affect inequalities in dementia in the future.
The age-adjusted prevalence of dementia tended to be higher among racial and ethnic minority individuals, both among men and women.
However, among men, the difference in the 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 fell from 17.2% to 9.9%.
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The study was conducted by Péter Hudomiet et al and published in the Proceedings of the National Academy of Sciences.
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