The presence of objective subtle cognitive difficulties (Obj-SCD) on neuropsychological measures may predict faster amyloid accumulation and neurogenerative changes prior to mild cognitive impairment (MCI), according to study results published in Neurology.
Previously, the researchers showed an association between Obj-SCD with cerebrospinal fluid Alzheimer disease markers and reported that Obj-SCD was associated with faster progression to MCI and dementia compared with patients with normal cognitive function. The goal of the study was to assess whether Obj-SCD predicts future amyloid accumulation and medical temporal lobe neurodegeneration.
The study was based on data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. The study cohort included 747 older adults without dementia, including 305 patients with normal cognitive function, 153 with Obj-SCD, and 289 with MCI. All patients had baseline florbetapir amyloid PET imaging and underwent neuropsychological testing and structural magnetic resonance imaging examinations.
Cognitive group status was used to estimate changes in amyloid positron emission tomography over 48 months. Relative to patients with normal cognitive function, patients with Obj-SCD had a faster increase in amyloid PET standardized uptake value ratio (SUVR) (P =.010). There was no statistically significant difference in the rate of amyloid accumulation between patients with MCI and patients with normal cognitive function or Obj-SCD.
Cognitive group also predicted entorhinal cortex thinning and hippocampal volume loss in the same period. Compared with patients with normal cognitive function, patients with Obj-SCD (P =.003) and MCI (P <.001) had faster entorhinal cortex thinning over 48 months. Relative to patients with normal cognitive function, patients with MCI had a faster rate of hippocampal volume loss over 48 months (P <.001), but there was no statistically significant difference between patients with Obj-SCD and patients with normal cognitive function or MCI.
The researchers noted several study limitations, including a cohort that is highly educated, mostly white, and generally healthy. The relatively short period of follow-up is another possible limitation.
The investigators concluded that while the operational definition of Obj-SCD, which incorporates neuropsychological process scores, has previously predicted progression to MCI and Alzheimer disease, these findings also suggest that Obj-SCD is “a sensitive and noninvasive predictor of future amyloid accumulation and early neurodegenerative changes, prior to frank cognitive impairment consistent with MCI.”
Thomas KR, Bangen KJ, Weigand AJ, et al. Objective subtle cognitive difficulties predict future amyloid accumulation and neurodegeneration [published online December 30, 2019]. Neurology. doi:10.1212/WNL.0000000000008838