new research shows. New data from the Health and Retirement Study, a nationally representative survey, show that the prevalence of dementia among individuals aged 65 and older dropped from 12.2% in 2000 to 8.5% in 2016 – a 30.1% decrease. In men, the prevalence of dementia fell from 10.2% to 7.0%, while for women, it declined from 13.6% to 9.7%, researchers reported. Their finding were published online in PNAS.
The study also revealed that the proportion of college-educated men in the sample increased from 21.5% in 2000 to 33.7% in 2016, while the proportion of college-educated women increased from 12.3% in 2000 to 23% in 2016.
The findings also show a decline in the dementia prevalence in non-Hispanic Black men, which dropped from 17.2% to 9.9%, a decrease of 42.6%. In non-Hispanic White men, dementia declined 9.3% to 6.6%, or 29.0%.
The investigators also found a substantial increase in the level of education between 2000 and 2016. In addition, they found that, among 74- to 84-year-old women in 2000, 29.5% had worked for more than 30 years during their lifetime versus 59.0% in 2016.
The investigators speculated that the decline in dementia prevalence reflects larger socioeconomic changes in the United States as well as prevention strategies to reduce cardiovascular disease.
A person born around 1920, for example, would have had greater exposure to the Great Depression, while someone born in 1936 would have benefited more from the changes in living standards in the years following World War II, they noted.
“There’s a need for more research on the effect of employment on cognitive reserve. It’s plausible that working is good for your mental cognitive abilities,” said study investigator Péter Hudomiet, PhD, from the RAND Corporation, adding that there may also be benefits that extend beyond working years. It’s possible that women’s greater participation in the workforce gives them more chances to establish relationships that in some cases last well into retirement and provide essential social connection. It’s well known that social isolation has a negative impact on cognition.
“It’s plausible that working is good for your mental cognitive abilities,” he added.
The investigators noted that it is beyond the scope of their study to draw definitive conclusions about the causes of the decline, but they observed that positive trends in employment and standard of living make sense. “They would suggest that as schooling levels continue to rise in the U.S. population in younger generations, the prevalence of dementia would continue to decrease.
The investigators report no relevant financial relationships.
A version of this article first appeared on Medscape.com.