Patients with Alzheimer’s disease (AD) who performed poorly on early cognitive tests seemed to progress more rapidly than those with less baseline impairment, a study showed.
Age was also an indicator of progression, with younger patients declining at a more rapid pace, according to the study published in the December issue of the American Journal of Alzheimer’s Disease & Other Dementias.
But no single test – even those routinely used as diagnostic tools – successfully predicted the rate of decline, reported Jennifer N. Travis Seidl and Paul J. Massman, Ph.D.
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“Tests that differed between the rapidly and slowly progressing groups tended to measure higher-order cognitive skills such as executive functioning, memory, and visuospatial construction,” wrote Ms. Seidl of the University of Houston and Dr. Massman of the Baylor College of Medicine, Houston. “This indicates that a full neuropsychological evaluation, rather than sole use of a global screening measure such as the MMSE [Mini-Mental State Exam] or ADAS-cog [Alzheimer’s Disease Assessment Scale–Cognitive], may be useful for predicting future cognitive decline.”
Although the individual course of Alzheimer’s dementia is notoriously unpredictable, the ability to predict the rate of decline would be immensely helpful to patients and caregivers, as well as medical staff, the investigators noted (Am J Alzheimers Dis Other Demen. 2015. doi: 10.1177/1533317515617720).
“Prediction of rate of decline among patients with [Alzheimer’s disease] may allow caregivers and physicians to make more informed decisions about future care of the patient,” they wrote.
The team examined dementia progression over a period of 2 years in a cohort of 110 Alzheimer’s patients who were seen at the Baylor College of Medicine Alzheimer’s Disease and Memory Disorders Center in Houston. Of these, half were slow progressers and the other half, rapid progressers.
The group was assessed by baseline and 2-year scores on 14 neuropsychological tests, including some of the most widely used: Mini-Mental State Examination, Clinical Dementia Rating scale (CDR), Alzheimer ’s Disease Assessment Scale–Cognitive subscale, and the Instrumental Activities of Daily Living (IADL). Other tests measured overall intelligence, memory and verbal fluency, executive function, and physical function.
At baseline, fast progression was significantly associated with younger age (72 vs. 77 years). Sex, ADAS-cog and MMSE scores, and apolipoprotein E epsilon 4 genetic status were not different between the groups. Functional status as measured by IADL was similar. The baseline CDR, however, was significantly different, with 48% of the slow progressers being at 0.5, compared with 24% of the rapid progressers.
The finding of no difference between the groups on baseline performance on the ADAS-cog or MMSE “indicates that these global measures are not as useful for predicting rate of decline as are more specific measures of neuropsychological functioning.”
Many of the more specific tests did accurately differentiate the groups. The rapid progressers had significantly poorer scores on the Logical Memory, Verbal Series Attention Test, Controlled Oral Word Association Test verbal fluency, and block design in the Wechsler Adult Intelligence Scale.
There were also persistent significant differences for the Boston Naming Test and Rey-Osterrieth Complex.
The investigators suggested that future research examine the predictive value of performance in tests that measure higher-order thinking skills “to determine whether the differences in the rate of progression observed in the current study occur throughout the course of the disease.”
They received no outside funding for the study and did not have any financial disclosures.
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