Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment

Nicholas I. Bradfield; Kathryn A. Ellis; Greg Savage; Paul Maruff; Samantha Burnham; David Darby; Nicola T. Lautenschlager; Ralph N. Martins; Colin L. Masters; Stephanie R. Rainey-Smith; Joanne Robertson; Christopher Rowe; Michael Woodward; David Ames

doi:10.1017/S135561772000079X

Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment

Nicholas I. Bradfield^*, Kathryn A. Ellis, Greg Savage, Paul Maruff, Samantha Burnham, David Darby, Nicola T. Lautenschlager, Ralph N. Martins, Colin L. Masters, Stephanie R. Rainey-Smith, Joanne Robertson, Christopher Rowe, Michael Woodward, David Ames

^*Corresponding author for this work

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Abstract

OBJECTIVES: The criteria for objective memory impairment in mild cognitive impairment (MCI) are vaguely defined. Aggregating the number of abnormal memory scores (NAMS) is one way to operationalise memory impairment, which we hypothesised would predict progression to Alzheimer's disease (AD) dementia.

METHODS: As part of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Ageing, 896 older adults who did not have dementia were administered a psychometric battery including three neuropsychological tests of memory, yielding 10 indices of memory. We calculated the number of memory scores corresponding to z ≤ -1.5 (i.e., NAMS) for each participant. Incident diagnosis of AD dementia was established by consensus of an expert panel after 3 years.

RESULTS: Of the 722 (80.6%) participants who were followed up, 54 (7.5%) developed AD dementia. There was a strong correlation between NAMS and probability of developing AD dementia (r = .91, p = .0003). Each abnormal memory score conferred an additional 9.8% risk of progressing to AD dementia. The area under the receiver operating characteristic curve for NAMS was 0.87 [95% confidence interval (CI) .81-.93, p < .01]. The odds ratio for NAMS was 1.67 (95% CI 1.40-2.01, p < .01) after correcting for age, sex, education, estimated intelligence quotient, subjective memory complaint, Mini-Mental State Exam (MMSE) score and apolipoprotein E ϵ4 status.

CONCLUSIONS: Aggregation of abnormal memory scores may be a useful way of operationalising objective memory impairment, predicting incident AD dementia and providing prognostic stratification for individuals with MCI.

Original language	English
Pages (from-to)	146–157
Number of pages	12
Journal	Journal of the International Neuropsychological Society
Volume	27
Issue number	2
Early online date	10 Aug 2020
DOIs	https://doi.org/10.1017/S135561772000079X
Publication status	Published - Feb 2021

Keywords

cognitive ageing
cognitive neuroscience
mild neurocognitive disorder
neuropsychology
neurocognitive disorders

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10.1017/S135561772000079X

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Bradfield, N. I., Ellis, K. A., Savage, G., Maruff, P., Burnham, S., Darby, D., Lautenschlager, N. T., Martins, R. N., Masters, C. L., Rainey-Smith, S. R., Robertson, J., Rowe, C., Woodward, M., & Ames, D. (2021). Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment. Journal of the International Neuropsychological Society, 27(2), 146–157. https://doi.org/10.1017/S135561772000079X

@article{7ccee90dfb4647fa92d2b788cde614ea,

title = "Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment",

abstract = "OBJECTIVES: The criteria for objective memory impairment in mild cognitive impairment (MCI) are vaguely defined. Aggregating the number of abnormal memory scores (NAMS) is one way to operationalise memory impairment, which we hypothesised would predict progression to Alzheimer's disease (AD) dementia.METHODS: As part of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Ageing, 896 older adults who did not have dementia were administered a psychometric battery including three neuropsychological tests of memory, yielding 10 indices of memory. We calculated the number of memory scores corresponding to z ≤ -1.5 (i.e., NAMS) for each participant. Incident diagnosis of AD dementia was established by consensus of an expert panel after 3 years.RESULTS: Of the 722 (80.6%) participants who were followed up, 54 (7.5%) developed AD dementia. There was a strong correlation between NAMS and probability of developing AD dementia (r = .91, p = .0003). Each abnormal memory score conferred an additional 9.8% risk of progressing to AD dementia. The area under the receiver operating characteristic curve for NAMS was 0.87 [95% confidence interval (CI) .81-.93, p < .01]. The odds ratio for NAMS was 1.67 (95% CI 1.40-2.01, p < .01) after correcting for age, sex, education, estimated intelligence quotient, subjective memory complaint, Mini-Mental State Exam (MMSE) score and apolipoprotein E ϵ4 status.CONCLUSIONS: Aggregation of abnormal memory scores may be a useful way of operationalising objective memory impairment, predicting incident AD dementia and providing prognostic stratification for individuals with MCI.",

keywords = "cognitive ageing, cognitive neuroscience, mild neurocognitive disorder, neuropsychology, neurocognitive disorders",

author = "Bradfield, {Nicholas I.} and Ellis, {Kathryn A.} and Greg Savage and Paul Maruff and Samantha Burnham and David Darby and Lautenschlager, {Nicola T.} and Martins, {Ralph N.} and Masters, {Colin L.} and Rainey-Smith, {Stephanie R.} and Joanne Robertson and Christopher Rowe and Michael Woodward and David Ames",

year = "2021",

month = feb,

doi = "10.1017/S135561772000079X",

language = "English",

volume = "27",

pages = "146–157",

journal = "Journal of the International Neuropsychological Society",

issn = "1355-6177",

publisher = "Cambridge University Press (CUP)",

number = "2",

}

Bradfield, NI, Ellis, KA, Savage, G, Maruff, P, Burnham, S, Darby, D, Lautenschlager, NT, Martins, RN, Masters, CL, Rainey-Smith, SR, Robertson, J, Rowe, C, Woodward, M & Ames, D 2021, 'Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment', Journal of the International Neuropsychological Society, vol. 27, no. 2, pp. 146–157. https://doi.org/10.1017/S135561772000079X

Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment. / Bradfield, Nicholas I.; Ellis, Kathryn A.; Savage, Greg et al.
In: Journal of the International Neuropsychological Society, Vol. 27, No. 2, 02.2021, p. 146–157.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia

T2 - a measure of objective memory impairment in amnestic mild cognitive impairment

AU - Bradfield, Nicholas I.

AU - Ellis, Kathryn A.

AU - Savage, Greg

AU - Maruff, Paul

AU - Burnham, Samantha

AU - Darby, David

AU - Lautenschlager, Nicola T.

AU - Martins, Ralph N.

AU - Masters, Colin L.

AU - Rainey-Smith, Stephanie R.

AU - Robertson, Joanne

AU - Rowe, Christopher

AU - Woodward, Michael

AU - Ames, David

PY - 2021/2

Y1 - 2021/2

N2 - OBJECTIVES: The criteria for objective memory impairment in mild cognitive impairment (MCI) are vaguely defined. Aggregating the number of abnormal memory scores (NAMS) is one way to operationalise memory impairment, which we hypothesised would predict progression to Alzheimer's disease (AD) dementia.METHODS: As part of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Ageing, 896 older adults who did not have dementia were administered a psychometric battery including three neuropsychological tests of memory, yielding 10 indices of memory. We calculated the number of memory scores corresponding to z ≤ -1.5 (i.e., NAMS) for each participant. Incident diagnosis of AD dementia was established by consensus of an expert panel after 3 years.RESULTS: Of the 722 (80.6%) participants who were followed up, 54 (7.5%) developed AD dementia. There was a strong correlation between NAMS and probability of developing AD dementia (r = .91, p = .0003). Each abnormal memory score conferred an additional 9.8% risk of progressing to AD dementia. The area under the receiver operating characteristic curve for NAMS was 0.87 [95% confidence interval (CI) .81-.93, p < .01]. The odds ratio for NAMS was 1.67 (95% CI 1.40-2.01, p < .01) after correcting for age, sex, education, estimated intelligence quotient, subjective memory complaint, Mini-Mental State Exam (MMSE) score and apolipoprotein E ϵ4 status.CONCLUSIONS: Aggregation of abnormal memory scores may be a useful way of operationalising objective memory impairment, predicting incident AD dementia and providing prognostic stratification for individuals with MCI.

AB - OBJECTIVES: The criteria for objective memory impairment in mild cognitive impairment (MCI) are vaguely defined. Aggregating the number of abnormal memory scores (NAMS) is one way to operationalise memory impairment, which we hypothesised would predict progression to Alzheimer's disease (AD) dementia.METHODS: As part of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Ageing, 896 older adults who did not have dementia were administered a psychometric battery including three neuropsychological tests of memory, yielding 10 indices of memory. We calculated the number of memory scores corresponding to z ≤ -1.5 (i.e., NAMS) for each participant. Incident diagnosis of AD dementia was established by consensus of an expert panel after 3 years.RESULTS: Of the 722 (80.6%) participants who were followed up, 54 (7.5%) developed AD dementia. There was a strong correlation between NAMS and probability of developing AD dementia (r = .91, p = .0003). Each abnormal memory score conferred an additional 9.8% risk of progressing to AD dementia. The area under the receiver operating characteristic curve for NAMS was 0.87 [95% confidence interval (CI) .81-.93, p < .01]. The odds ratio for NAMS was 1.67 (95% CI 1.40-2.01, p < .01) after correcting for age, sex, education, estimated intelligence quotient, subjective memory complaint, Mini-Mental State Exam (MMSE) score and apolipoprotein E ϵ4 status.CONCLUSIONS: Aggregation of abnormal memory scores may be a useful way of operationalising objective memory impairment, predicting incident AD dementia and providing prognostic stratification for individuals with MCI.

KW - cognitive ageing

KW - cognitive neuroscience

KW - mild neurocognitive disorder

KW - neuropsychology

KW - neurocognitive disorders

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U2 - 10.1017/S135561772000079X

DO - 10.1017/S135561772000079X

M3 - Article

C2 - 32772959

AN - SCOPUS:85089739759

SN - 1355-6177

VL - 27

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JO - Journal of the International Neuropsychological Society

JF - Journal of the International Neuropsychological Society

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Bradfield NI, Ellis KA, Savage G, Maruff P, Burnham S, Darby D et al. Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment. Journal of the International Neuropsychological Society. 2021 Feb;27(2):146–157. Epub 2020 Aug 10. doi: 10.1017/S135561772000079X

Aggregation of abnormal memory scores and risk of incident Alzheimer's disease dementia: a measure of objective memory impairment in amnestic mild cognitive impairment

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