Patients with Alzheimer’s disease who perform poorly on early cognitive tests may progress more rapidly than those with less baseline impairment, according to research published online ahead of print December 8, 2015, in American Journal of Alzheimer’s Disease & Other Dementias. Age also may predict rate of progression; younger patients may decline at a more rapid pace, said the authors.
No single test, including those routinely used as diagnostic tools, successfully predicted participants’ rate of decline, said Paul J. Massman, PhD, Associate Professor of Clinical Psychology at Baylor College of Medicine in Houston. “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,” said Dr. Massman. “This [result] indicates that a full neuropsychologic evaluation, rather than sole use of a global screening measure such as the Mini-Mental State Examination [MMSE] or Alzheimer’s Disease Assessment Scale–Cognitive [ADAS-Cog], 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 help patients and caregivers, as well as medical staff, said the investigators. “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.”
The team examined dementia progression over a period of two years in 110 patients with Alzheimer’s disease who were seen at the Baylor College of Medicine Alzheimer’s Disease and Memory Disorders Center. Of these participants, half had slow disease progression and half had rapid disease progression.
The group was assessed at baseline and at two years with 14 neuropsychologic tests, including the MMSE, Clinical Dementia Rating scale (CDR), ADAS-Cog, 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 (age 72 vs age 77). Sex, ADAS-Cog and MMSE scores, and APOE4 genetic status were not different between the groups. Functional status, as measured by IADL, was similar. The baseline CDR score, however, was significantly different. Approximately 48% of slow progressers had a score of 0.5, compared with 24% of rapid progressers. The lack of difference between the groups at baseline 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 neuropsychologic functioning,” said the authors.
Many of the more specific tests accurately differentiated between 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.”
—Michele G. Sullivan