Three cognitive trajectories identified in preclinical Alzheimer’s disease

Cognitive decline in Alzheimer's disease differs substantially from one person to the next and is not well predicted by existing medical tests. Among people with preclinical Alzheimer's disease who began one of two related studies with no symptoms, researchers from the Keck School of Medicine of USC found three distinct patterns: stable, slow cognitive decline and fast cognitive decline. About 70% of participants remained stable over the study period of approximately six years. The research, funded in part by the National Institutes of Health, was just published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.

"Most studies look at the average across participants, which can make it seem like everyone is slowly getting worse at the same rate," said the paper's corresponding author, Michael Donohue, PhD, professor of neurology and associate director of biostatistics at the USC Epstein Family Alzheimer's Therapeutic Research Institute at the Keck School of Medicine. "But we found that this approach masks major differences between people, suggesting that Alzheimer's disease is more variable than often depicted."

While prior research suggested that people with Alzheimer's disease decline at different rates, the present study is one of the first to tie those patterns to biomarker data. The researchers tested whether certain biomarkers, including specific blood tests and brain scans, could predict who was likely to remain stable and who was likely to worsen. Their models classified participants with about 70% accuracy.

Though it needs further refinement, this kind of prediction tool could someday give patients a more accurate prognosis when they are diagnosed with Alzheimer's disease. Better predictive models could also support more effective clinical trials of potential treatments. The researchers say current trials may be oversimplifying the disease by assuming everyone follows the same path.