Mild cognitive impairment: a cross-national comparison
- 1Karolinska Institutet, Neurotec Department, Division of Clinical Geriatrics, Huddinge University Hospital, Stockholm, Sweden
- 2Department of Psychiatry and Psychology, Mayo Clinic and Mayo Foundation, Rochester, MN, USA
- 3Department of Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, MN, USA
- 4Department of Neurology, Mayo Clinic and Mayo Foundation, Rochester, MN, USA
- Correspondence to: O Almkvist Division of Clinical Geriatrics, Huddinge University Hospital B84, S-141 86 Stockholm, Sweden; ove.almkvistneurotec.ki.se
- Received 2 May 2003
- Accepted 1 December 2003
- Revised 28 November 2003
Abstract
Objective: The main aim of this collaborative study was to assess the comparability of the most commonly used criteria for mild cognitive impairment (MCI) by comparing the cognitive performance of patients with MCI from the Mayo Clinic (USA) and the Karolinska Institutet (Sweden).
Methods: Standardised neuropsychological test scores were used to compare the two samples from the two institutions with regard to the number of cognitive domains in which performance was below 1.5 SD. Possible predictors for the conversion from MCI to Alzheimer’s disease (AD) were assessed.
Results: When the two institutions were considered together in the Cox proportional hazard model, the number of affected cognitive domains below 1.5 SD was a significant predictor of time to AD diagnosis with age, education, and APOE ε4 genotype entered into the same model as covariates. The number of affected cognitive areas remained as a significant predictor when the institutions were considered separately. The logistic regression model of conversion to AD showed that only tests assessing learning and retention were predictors of developing AD.
Conclusions: Differences in population as well as in methodology of case ascertainment as well as other aspects may account for the observed variability between samples of patients with MCI. The number of impaired cognitive factors at baseline can predict the progression from MCI to AD. Furthermore, tests assessing learning and retention are the best predictors for progression to AD.
- AD, Alzheimer’s disease
- AVLT, Auditory Verbal Learning Test
- CDR, Clinical Dementia Rating (scale)
- KI, Karolinska Institute
- MC, Mayo Clinic
- MCFS, Mayo Cognitive Factor Scores
- MCI, mild cognitive impairment
- WAIS-R, Wechsler Adult Intelligence Scale-Revised
- WMS-R, Wechsler Memory Scale-Revised
Footnotes
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This work was supported by the Margit and Folke Pehrzon Foundation, the Gamla Tjännarinor Foundation, Swedish Research Council, and Alzheimerfonden.
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The Mayo work was supported by grants from the National Institute on Aging, Mayo Clinic Alzheimer’s Disease Center AG 16574 and Alzheimer’s Disease Patient Registry AG 06786.
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Competing interests: Ronald C Petersen receives funding for research on mild cognitive impairment through a consortium involving the National Institute on Aging and the University of California—San Diego from Pfizer, Inc and Eisai, Inc. He also receives consulting fees from Elan Pharmaceuticals/Wyeth, Inc. He has received honoraria for speaking from several pharmaceutical companies including Pfizer, Eisai, Novartis and Janssen, but these are through national organisations such as the American Academy of Neurology or through universities and medical centres using unrestricted educational grants. He has attended a symposium on mild cognitive impairment sponsored by Mount Sinai Medical Centre in Miami which was supported by pharmaceutical company grants. He is a consultant to the Loma Linda University.
