Happy caregiver man helping and supporting senior woman sitting outdoors in park.
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The prevalence of dementia in older adults in the United States declined 30% between 2000 and 2016, possibly due to rising education levels, a reduction in smoking and better treatment of cardiovascular risk factors, according to a new study published Monday in the journal Proceedings of the National Academy of Sciences.

Overall, researchers from the nonprofit group the RAND Corp. found the prevalence of dementia had decreased substantially in the US older adult population since 2000, declining from 12.2% of older adults in 2000 to 8.5% in 2016, an almost one-third drop. 

The gap in dementia prevalence narrowed between men and women, and inequalities decreased between education, income, and race and ethnicity groups, especially among men.

The prevalence of dementia was higher among women than men over the study period, but differences shrank in that time. Among men, the prevalence of dementia decreased from 10.2% to 7%, whereas decreases were larger among women, dropping from 13.6% to 9.7%.

“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,” Peter Hudomiet, the study’s lead author and a RAND economist, stated in a release. “This decline may help reduce the expected strain on families, nursing homes and other support systems as the American population ages.”

The economic cost of dementia was estimated at $200 billion per year in the United States and $600 billion worldwide, making it the most expensive of all medical conditions, according to the authors. In 2021, approximately 6.2 million US adults aged 65 or more years lived with dementia. Because age is the strongest risk factor for dementia, increasing life expectancy is predicted to substantially increase the prevalence of Alzheimer’s disease and related dementias between 50 to 150 million worldwide by 2050, according to the report.

Researchers found that education is a “very strong” predictor of dementia, and that there was a sizable increase in the average level of education over the study period. Education rates alone explained a 40% reduction in dementia prevalence among men and a 20% reduction among women. The number of college-educated men in the study increased from 21.5% in 2000 to 33.7% in 2016, whereas college education rates for women increased from 12.3% to 23%.

Changes in factors including age, race and ethnicity, as well as cardiovascular risk factors, mattered less in determining the prevalence of dementia. 

The authors stated the results suggest that as education levels continue to rise in the US population in younger generations, the prevalence of dementia would continue to decrease. Changes in age-specific rates of dementia have important implications for projected prevalence and costs, including payments for long-term care by families, insurance companies and the government.

“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,” the authors wrote. 

The National Bureau of Economic Research in Cambridge, MA, and Network for Studies on Pensions, Aging and Retirement in the Netherlands contributed to the study, which was supported by a grant from the National Institute on Aging.