Familial risks for Alzheimer disease from a population-based series

Area of Science:

• Neuroscience
• Genetics
• Epidemiology

Background:

• Alzheimer disease (AD) is a progressive neurodegenerative disorder.
• Understanding the genetic risk factors for AD is crucial for developing effective interventions.
• Previous studies have suggested a genetic component to AD, but the exact mode of transmission remains debated.

Purpose of the Study:

• To estimate the lifetime risk of developing Alzheimer disease (AD) in first-degree relatives.
• To compare risk estimates between two consecutive cohorts of relatives.
• To evaluate the consistency of case ascertainment over time.

Main Methods:

• Kaplan-Meier survival analysis was used to estimate cumulative risks.
• Two independent series of first-degree relatives of AD patients were analyzed (N1 = 840, N2 = 819).
• Probable and autopsy-confirmed AD diagnoses were included.

Main Results:

• The combined lifetime risk estimate for Alzheimer disease (AD) up to age 88 was 23.4% (± 3.0%).
• Risk estimates were consistent across the two series, indicating reliable case ascertainment over 8 years.
• The observed risk is significantly lower than the 50% risk expected under an autosomal dominant inheritance model.

Conclusions:

• The findings do not support a simple autosomal dominant inheritance model for all Alzheimer disease (AD) cases.
• The results reinforce previous evidence suggesting complex genetic and environmental factors contribute to AD etiology.
• Consistent risk estimates provide confidence in the study's methodology and findings regarding familial AD risk.