A new study in 'Nature Medicine' identifies two copies of the APOE4 gene as a definitive cause of Alzheimer's, not just a risk factor.

Analysis of 3,297 donated brains and 10,039 individuals showed that double APOE4 carriers exhibit more disease biomarkers post-55, have abnormal amyloid levels, and experience earlier symptom onset.

The discovery is pivotal for future Alzheimer's research, diagnosis, and treatment, aligning with emerging drugs like Leqembi and donanemab.

There is a recognized need for therapies targeting the APOE4 protein, which may shift research strategies in Alzheimer's disease.

Despite these findings, APOE4 genetic testing is not currently advocated in Germany, and upcoming EU antibody therapies show increased side effects in APOE4 carriers.

The study advocates for the inclusion of double APOE4 carriers in preventative trials and calls for more diverse research to assess Alzheimer's risk across different ancestries.