Clinical and biomarker changes in dominantly inherited Alzheimer's disease.
Level 3 - non-randomized controlled study
Prospective cohort study analyzing baseline biomarker and clinical trajectories.
PubMed 22784036 · doi:10.1056/NEJMoa1202753
What was done
Cross-sectional analysis of baseline data from a prospective longitudinal cohort of 128 participants with or at risk for autosomal dominant Alzheimer's disease. Participants underwent clinical and cognitive assessments, brain imaging (positron-emission tomography with Pittsburgh compound B, structural MRI, and metabolic imaging), and cerebrospinal fluid (CSF) and blood tests. Researchers analyzed changes in relation to estimated years from expected symptom onset, calculated as the participant's age at assessment minus their parent's age at symptom onset.
What was found
Pathophysiological and clinical changes were detected in a specific chronological sequence: - CSF Aβ42 concentrations declined 25 years before expected symptom onset. - Brain amyloid-beta deposition on PET, increased CSF tau concentrations, and brain atrophy were detected 15 years before expected symptom onset. - Cerebral hypometabolism and impaired episodic memory appeared 10 years before expected symptom onset. - Global cognitive impairment (Mini-Mental State Examination and Clinical Dementia Rating) was detected 5 years before expected symptom onset. - Dementia diagnostic criteria were met at an average of 3 years after expected symptom onset.
Why it matters
This study maps a multi-decade timeline of preclinical biomarker changes in autosomal dominant Alzheimer's disease, showing that pathology begins 25 years before clinical onset and providing a benchmark for the timing of early therapeutic interventions.
Limits
The chronological sequence was modeled cross-sectionally using parental age of onset rather than direct within-individual longitudinal follow-up. The findings are based on a cohort of 128 individuals with rare genetic mutations and may not generalize to sporadic Alzheimer's disease.
Cited by
- supports Neurodegenerative conditions like Alzheimer's begin 20 to 30 years prior to the presentation of clinical symptoms.