One in 10 Americans over 65 had dementia, while 22% experienced mild cognitive impairment, the earliest stage of the slow slide into senility, according to a new study conducted between 2016 and 2017.
The research, which the authors said is the first nationally representative examination of cognitive impairment prevalence in more than 20 years, was able to measure prevalence of dementia and mild cognitive impairment by age, education, ethnicity, gender and race.
The results showed older adults who self-identified as Black or African American were more likely to have dementia, while those who identify as Hispanic were more likely to suffer from mild cognitive impairment. People who had less than a high school education were more likely to have both conditions.
“Dementia research in general has largely focused on college-educated people who are racialized as white,” lead study author Jennifer Manly said in a statement.
“This study is representative of the population of older adults and includes groups that have been historically excluded from dementia research but are at higher risk of developing cognitive impairment because of structural racism and income inequality,” said Manly, professor of neuropsychology at the Gertrude H. Sergievsky Center and the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at Columbia University.
“If we’re interested in increasing brain health equity in later life, we need to know where we stand now and where to direct our resources,” Manly said.
The study, published Monday in the journal JAMA Neurology, analyzed data from in-depth neuropsychological tests and interviews with nearly 3,500 people over age 65 enrolled in the Health and Retirement Study, a long-term research project sponsored by the National Institute on Aging and the Social Security Administration.
The research was based on a randomly selected sample of people from the study that completed the core survey and underwent neurological testing between June 2016 and October 2017.
Fifteen percent of people who identified as Black tested positive for dementia, while 22% had mild cognitive decline, the study found. Ten percent of people who identified as Hispanic had dementia, but the rate of milder issues was higher — 28% tested positive for mild cognitive impairment. Nine percent of White people had dementia, while 21% had mild cognitive impairment.
Educational achievement, which experts consider to be protective against cognitive decline, showed a significant divide: Nine percent of people with a college degree tested positive for dementia, compared with 13% of those who never received a high school diploma. Twenty-one percent of people over 65 with college degrees had mild cognitive decline, compared with 30% of those with less than a high school degree.
The extreme elderly had the highest rates of dementia and mild cognitive impairment. Only 3% of adults between 65 and 69 tested positive for dementia, compared with 35% of those 90 and older.