Prevalence of Cognitive Impairment without Dementia in the United States

18 March 2008 | Volume 148 Issue 6 | Pages 427-434

Background: 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.

Objective: To estimate the prevalence of cognitive impairment without dementia in the United States and determine longitudinal cognitive and mortality outcomes.

Design: Longitudinal study from July 2001 to March 2005.

Setting: In-home assessment for cognitive impairment.

Participants: 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.

Measurements: 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.

Results: 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.

Limitations: 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.

Conclusion: Cognitive impairment without dementia is more prevalent in the United States than dementia, and its subtypes vary in prevalence and outcomes.

Editors' Notes Context How common is mild cognitive impairment in older adults? Contribution This study of 856 individuals from the national Health and Retirement Study found that 22% of adults age 71 or older had cognitive impairment that did not reach the threshold for dementia. Annually, about 8% of those with cognitive impairment without dementia died and about 12% progressed to dementia. Caution Criteria that differentiate mild impairment from dementia are imperfect. Only 856 of 1770 and 180 of 241 selected individuals completed baseline and follow-up cognitive examinations, respectively. Implication Cognitive impairment without dementia probably affects a large segment of the elderly population. —The Editors

 

Author and Article Information

From Duke University Medical Center, Durham, North Carolina; University of Michigan and Veterans Affairs Center for Practice Management and Outcomes Research, Ann Arbor, Michigan; RAND Corporation, Santa Monica, California; University of Southern California, Los Angeles, California; and University of Iowa, Iowa City, Iowa.

Acknowledgment: The authors gratefully acknowledge the scientific and clinical input of the other members of the consensus conference panel: Kathleen A. Welsh-Bohmer, PhD; John C.S. Breitner, MD; Norman L. Foster, MD; Bruno Giordani, PhD; Hugh Hendrie, MB, ChB, DSc; and Frederick W. Unverzagt, PhD. Drs. Breitner and Welsh-Bohmer were involved in the early planning and development of ADAMS and in obtaining the project funding. The authors also acknowledge the invaluable contributions of the ADAMS participants and the research staff at Duke University Medical Center and the University of Michigan.

Grant Support: By the National Institute on Aging (U01 AG09740). Dr. Langa was supported by National Institute on Aging grants K08 AG019180 and R01 AG027010 and a Paul Beeson Physician Faculty Scholars award.

Potential Financial Conflicts of Interest: None disclosed.

Reproducible Research Statement: The study protocol and data are available on the HRS Web site (http://hrsonline.isr.umich.edu/adams/overview/summary_2.htm). The statistical code is available to interested readers by contacting Dr. Heeringa (e-mail, sheering{at}isr.umich.edu) or Dr. Fisher (e-mail, gwenithf{at}isr.umich.edu).

Requests for Single Reprints: Brenda L. Plassman, PhD, 905 West Main Street, Suite 25-D, Box 41, Duke University Medical Center, Durham, NC 27701; e-mail, brenda.plassman{at}duke.edu.

Current Author Addresses: Drs. Plassman, Potter, and Steffens: 905 West Main Street, Box 41, Suite 25-D, Durham, NC 27701.

Dr. Langa: 300 North Ingalls Building, Room 7E01, Ann Arbor, MI 48109-0429.

Drs. Fisher, Heeringa, Weir, Ofstedal, and Willis: 426 Thompson Street, Ann Arbor, MI 48104.

Dr. Burke: Box 2900, Duke University Medical Center, Durham, NC 27710.

Dr. Hurd: 1776 Main Street, PO Box 2138, Santa Monica, CA 90407-2138.

Dr. Rodgers: 2050 West 22nd Avenue, Eugene, OR 97405.

Dr. McArdle: 3620 South McClintock Avenue, SGM 501, Los Angeles, CA 90089-1061.

Dr. Wallace: 200 Hawkins Drive, C21-N GH, Iowa City, IA 52242.

Author Contributions: Conception and design: B.L. Plassman, K.M. Langa, G.G. Fisher, S.G. Heeringa, D.R. Weir, M.B. Ofstedal, J.R. Burke, M.D. Hurd, G.G. Potter, W.L. Rodgers, D.C. Steffens, R.J. Willis, R.B. Wallace.

Analysis and interpretation of the data: B.L. Plassman, K.M. Langa, G.G. Fisher, S.G. Heeringa, D.R. Weir, M.B. Ofstedal, J.R. Burke, M.D. Hurd, G.G. Potter, W.L. Rodgers, D.C. Steffens, J.J. McArdle, R.B. Wallace.

Drafting of the article: B.L. Plassman, K.M. Langa, G.G. Fisher.

Critical revision of the article for important intellectual content: B.L. Plassman, K.M. Langa, G.G. Fisher, S.G. Heeringa, D.R. Weir, M.B. Ofstedal, J.R. Burke, M.D. Hurd, G.G. Potter, W.L. Rodgers, D.C. Steffens, J.J. McArdle, R.J. Willis, R.B. Wallace.

Final approval of the article: B.L. Plassman, K.M. Langa, G.G. Fisher, S.G. Heeringa, D.R. Weir, M.B. Ofstedal, J.R. Burke, M.D. Hurd, G.G. Potter, W.L. Rodgers, D.C. Steffens, J.J. McArdle, R.J. Willis, R.B. Wallace.

Statistical expertise: B.L. Plassman, K.M. Langa, G.G. Fisher, S.G. Heeringa, D.R. Weir, M.D. Hurd, J.J. McArdle, W.L. Rodgers.

Obtaining of funding: B.L. Plassman, K.M. Langa, S.G. Heeringa, D.R. Weir, M.B. Ofstedal, M.D. Hurd, W.L. Rodgers, R.J. Willis, R.B. Wallace.

Administrative, technical, or logistic support: B.L. Plassman, G.G. Fisher, S.G. Heeringa, J.R. Burke, G.G. Potter, D.C. Steffens.

Collection and assembly of data: B.L. Plassman, K.M. Langa, G.G. Fisher, M.B. Ofstedal, J.R. Burke, G.G. Potter, D.C. Steffens, R.B. Wallace.

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Erratum Statement for our article: Prevalence of Cognintive Impairment without Dementia in the U.S.

Brenda Plassman, et al.

Annals Online, 26 Jun 2009 [Full text]