Is Memory an Effective Screening Measure for Alzheimer Disease?

Low memory and cognition scores may not be an effective screening method for early Alzheimer disease (AD) among individuals without dementia, according to a recent study.

Cerebral amyloid-β aggregation is known to occur in early AD. For their ongoing study, the researchers have been investigating whether amyloid-β aggregation is associated with cognitive functioning in individuals without dementia. Participants were classified as having normal cognition (n = 2908; mean age 67.4 years) or mild cognitive impairment (n = 4133; mean age 70.2 years).
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Participants were administered the Mini-Mental State Examination (MMSE) to evaluate global cognitive performance, as well as a verbal word learning test to assess episodic memory performance. Positron emission tomography or cerebrospinal fluid biomarkers were used to measure amyloid aggregation, which was subsequently classified as negative (normal) or positive (abnormal). The association between amyloid aggregation and low cognitive scores, as well as factors that may influence it, were analyzed via generalized estimating equations.

Results of a 2017 data analysis indicated that amyloid positivity was linked to low memory scores after age 70 years in participants with normal cognition (mean difference in amyloid positive vs negative, 4% at 72 years and 21% at 90 years), but was not related to low MMSE scores (mean difference 3%). However, both of these measures were associated with amyloid positivity (mean difference 16% and 14%, respectively). This association was found to decrease with age.

Ultimately, the researchers concluded that low cognitive scores were limited in their ability to screen for amyloid positivity in individuals with normal cognition or mild cognitive impairment. Notably though, the researchers noted that the age-related increase in low memory score paralleled the age-related increase in amyloid positivity among individuals with normal cognition (intervening period, 10 to 15 years).

“Although low memory scores are an early marker of amyloid positivity, their value as a screening measure for early AD among persons without dementia is limited,” the researchers concluded.

—Christina Vogt

Reference:

Jansen WJ, Ossenkoppele R, Tijms BM, et al; Amyloid Biomarker Study Group. Association of cerebral amyloid-β aggregation with cognitive functioning in persons without dementia. JAMA Psychiatry. 2018;75(1):84-95. doi:10.1001/jamapsychiatry.2017.3391.