The study was released on Monday JAMA Neurology found that nearly a third of Americans age 65 and older in 2016 had dementia or mild cognitive impairment, but prevalence varied by age, education, race, and ethnicity.
Study details and key findings
For the study, researchers collected data from 3,496 participants in the Harmonized Cognitive Assessment Protocol (HCAP) project, who are part of the ongoing, longitudinal Health and Retirement Study (HRS). A random sample of HRS participants aged 65 and older in 2016 was included in the HCAP.
Since 2016 in June until 2017 October month. HCAP participants had to complete a comprehensive neuropsychological test and a personal interview.
On average, participants were 76.4 years old. Of the total, 60% were female, 71% self-identified as white, 16% as black, 11% as Hispanic, and 2% as other races.
Dementia and mild cognitive impairment were classified according to an algorithm based on standard diagnostic criteria. The researchers then compared the participants’ test scores to a normative sample. To estimate the prevalence of dementia and mild cognitive impairment in the United States, the researchers used population weights.
According to study author Jennifer Manly of Columbia University Irving Medical Centerand colleagues, 2016 10% of participants had dementia and 22% had mild cognitive impairment.
Although the prevalence of dementia was similar between men and women, it varied by age, education, race, and ethnicity.
For example, compared with white participants, dementia was more common among black participants, and mild cognitive impairment was more common among Hispanic participants.
With each five-year increase in age, participants experienced an increased risk of dementia and mild cognitive impairment. For example, 35% of people aged 90 and over had dementia, a significant jump from just 3% of participants aged 65-69.
The study also found that “each additional year of schooling was associated with a reduction in the risk of dementia.”
Although the findings mark the first representative study of cognitive impairment in more than 20 years, the study authors noted that the findings echo other recent estimates of dementia prevalence in the United States.
Because the findings represent a snapshot, they cannot accurately estimate cognitive impairment or rate of progression among individuals with mild cognitive impairment, the authors said.
In addition, the authors noted that other longitudinal studies have shown that classifications of mild cognitive impairment may be inconsistent, as many people fall into the normal cognitive classification at subsequent encounters.
Finally, the cross-sectional design of the HCAP study “does not allow for survival bias, which may increase prevalence if some groups live longer with dementia or reduce estimates in groups with higher mortality,” the authors added.
However “[b]Because the HCAP study is part of a nationally representative and longitudinal study of health and retirement, these data not only show the burden of dementia now, but will also be used in the future to track trends in the burden of dementia over the coming decades. said co-author Kenneth Langa University of Michigan.
“With increasing longevity and the aging of the Baby Boom generation, cognitive impairment is projected to increase dramatically over the next few decades, impacting individuals, families and programs that provide care and services to people with dementia,” Manly said.
“Following these trends will be especially important given the potential impact of COVID and other recent population health changes on dementia risk in the coming decades,” Langa added. (George, MedPage today, 10/24; Muller, A hill, 10/24; Manly et al., JAMA Neurology10/24 [subscription required])