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From the University of Oxford, Oxford Project to Investigate Memory and Ageing (OPTIMA), John Radcliffe Hospital (A.O., G.K.W., A.D.S., C.A.d.J.), Oxford; and Department of Physiology, Anatomy and Genetics (A.D.S.) and Nuffield Department of Clinical Medicine (G.K.W.), University of Oxford, UK.
Address correspondence and reprint requests to Prof. A. David Smith, OPTIMA, Level 4, John Radcliffe Hospital, Oxford OX3 9DU, UK david.smith{at}dpag.ox.ac.uk
Background: Increasing awareness that minimal or mild cognitive impairment (MCI) in the elderly may be a precursor of dementia has led to an increase in the number of people attending memory clinics. We aimed to develop a way of predicting the period of time before cognitive impairment occurs in community-dwelling elderly. The method is illustrated by the use of simple tests of different cognitive domains.
Methods: A cohort of 241 normal elderly volunteers was followed for up to 20 years with regular assessments of cognitive abilities using the Cambridge Cognitive Examination (CAMCOG); 91 participants developed MCI. We used interval-censored survival analysis statistical methods to model which baseline cognitive tests best predicted the time to convert to MCI.
Results: Out of several baseline variables, only age and CAMCOG subscores for expression and learning/memory were predictors of the time to conversion. The time to conversion was 14% shorter for each 5 years of age, 17% shorter for each point lower in the expression score, and 15% shorter for each point lower in the learning score. We present in tabular form the probability of converting to MCI over intervals between 2 and 10 years for different combinations of expression and learning scores.
Conclusion: In apparently normal elderly people, subtle measurable cognitive deficits that occur within the normal range on standard testing protocols reliably predict the time to clinically relevant cognitive impairment long before clinical symptoms are reported.
Abbreviations: AD = Alzheimer disease; AFT = accelerated failure time; aMCI = amnestic mild cognitive impairment; CAMCOG = Cambridge Cognitive Examination; CAMDEX = Cambridge Examination for Disorders of the Elderly; CI = confidence interval; MCI = mild cognitive impairment; MMSE = Mini-Mental State Examination; NINCDS = National Institute of Neurological and Communicative Disorders and Stroke; OPTIMA = Oxford Project to Investigate Memory and Ageing; OR = odds ratio.
Supplemental data at www.neurology.org
Editorial, page 1432
e-Pub ahead of print at www.neurology.org.
During the course of the study, the principal grant support for OPTIMA came from Bristol-Myers Squibb, Merck & Co. Inc., Medical Research Council, Charles Wolfson Charitable Trust, Alzheimer's Research Trust, and Norman Collisson Foundation. Dr. Wilcock was partly supported by the NIHR Biomedical Research Centre, Oxford.
Disclosure: The authors report no disclosures.
Received April 23, 2009. Accepted in final form August 4, 2009.
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Neurology 2009 73: 1432-1433.
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  M. F. Elias and A. Davey Predicting conversion to mild cognitive impairment: Some error is the price of much truth Neurology, November 3, 2009; 73(18): 1432 - 1433. [Full Text] [PDF]
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