Cognitive impairment without dementia is associated with increased risk for disability,
increased health care costs, and progression to dementia. There are no population-based
prevalence estimates of this condition in the United States.
To estimate the prevalence of cognitive impairment without dementia in the United
States and determine longitudinal cognitive and mortality outcomes.
Longitudinal study from July 2001 to March 2005.
In-home assessment for cognitive impairment.
Participants in ADAMS (Aging, Demographics, and Memory Study) who were age 71 years
or older drawn from the nationally representative HRS (Health and Retirement Study).
Of 1770 selected individuals, 856 completed initial assessment, and of 241 selected
individuals, 180 completed 16- to 18-month follow-up assessment.
Assessments, including neuropsychological testing, neurologic examination, and clinical
and medical history, were used to assign a diagnosis of normal cognition, cognitive
impairment without dementia, or dementia. National prevalence rates were estimated
by using a population-weighted sample.
In 2002, an estimated 5.4 million people (22.2%) in the United States age 71 years
or older had cognitive impairment without dementia. Prominent subtypes included prodromal
Alzheimer disease (8.2%) and cerebrovascular disease (5.7%). Among participants who
completed follow-up assessments, 11.7% with cognitive impairment without dementia
progressed to dementia annually, whereas those with subtypes of prodromal Alzheimer
disease and stroke progressed at annual rates of 17% to 20%. The annual death rate
was 8% among those with cognitive impairment without dementia and almost 15% among
those with cognitive impairment due to medical conditions.
Only 56% of the nondeceased target sample completed the initial assessment. Population
sampling weights were derived to adjust for at least some of the potential bias due
to nonresponse and attrition.
Cognitive impairment without dementia is more prevalent in the United States than
dementia, and its subtypes vary in prevalence and outcomes.