APOE4 gene

APOE4, a form of the apolipoprotein E gene, is a genetic risk factor for developing dementia, including Alzheimer’s disease. According to the National Institute of Aging (NIA), roughly 25% of the human population carries one copy of APOE4. And ~2-3% of people carry two copies of the gene.

While there is a strong association between carriers and those who develop dementia (APOE4 is carried by almost half of all Alzheimer’s patients), inheriting the gene doesn’t ensure one will certainly develop the disease. However, those with two copies of the gene reportedly have an 8-12 times greater chance of developing the disease.

Genetic Variants

There are three main variants of the gene: APOE2, APOE3, and APOE4. Each person inherits one copy of the APOE gene from each parent, resulting in a combination of two alleles. The APOE4 allele is associated with an increased risk of certain health conditions, particularly in the realm of neurodegenerative diseases.

APOE4 and Alzheimer's Disease

One of the most extensively studied associations of the gene is its link to Alzheimer's disease (AD). Individuals who inherit one copy of the APOE4 allele have an increased risk of developing Alzheimer's, while those with two copies face an even higher risk. Research indicates that APOE4 may contribute to the accumulation of beta-amyloid plaques in the brain, a hallmark of Alzheimer's disease.

Mechanisms of Action

The exact mechanisms through which APOE4 influences Alzheimer's risk are still under investigation. Some studies suggest that APOE4 may impair the clearance of beta-amyloid from the brain, leading to its accumulation. Additionally, the gene may impact inflammatory responses and the overall health of neurons, contributing to cognitive decline.

Cognitive Function

Apart from its association with Alzheimer's disease, APOE4 has also been linked to changes in cognitive function in individuals without dementia. Research has shown that even in healthy individuals, possessing the APOE4 allele may be associated with subtle cognitive differences and alterations in brain structure.

Genetic Testing for APOE4

Given the potential implications on health, some individuals may choose to undergo genetic testing. However, it's important to note that possessing the APOE4 allele does not guarantee the development of Alzheimer's disease, and not having the allele does not ensure immunity. 

Lifestyle Factors

While genetics play a role, lifestyle factors such as diet, exercise, and cognitive engagement also influence the risk of developing Alzheimer's disease. Research suggests that individuals with the APOE4 allele may benefit even more from adopting a healthy lifestyle to mitigate their risk.

Chris Hemsworth, APOE4, and Furture Warnings

Discussions about APOE4 became more mainstream after celebrity Chris Hemsworth discovered he carried the gene. The discovery occured during the filming of the longevity docuseries "Limitless," when Hemsworth received the results of a standardized genetics test. Hemsworth subsequently announced he'd be taking a break from acting to focus on his family and health. 

Current Research and Future Directions

Ongoing research continues to explore the intricacies of the APOE4 gene and its implications for neurological health. Scientists are investigating potential therapeutic interventions that target APOE4-related pathways, with the aim of developing treatments to reduce the risk or slow the progression of Alzheimer's disease.

Conclusion

The APOE4 gene is a key player in the complex landscape of neurodegenerative diseases, particularly Alzheimer's disease. While possessing the APOE4 allele may increase the risk of cognitive decline, it is essential to approach this information with nuance. The interplay between genetics and lifestyle factors underscores the importance of a holistic approach to brain health.