BLOG | Genetics and environment: a key combination in aging and Alzheimer’s disease

If my parents had Alzheimer’s, will I also have Alzheimer’s? That is the question many people ask their trusted doctors. And the answer is: not necessarily.

Leaving aside the 1% of cases in which Alzheimer’s is due to mutations in one of the three key genes for this disease (APP, PSEN1, and PSEN2), 95% of Alzheimer’s cases are what are known as sporadic. In these cases, genetics still plays an essential role, as 65% of this disease is due to the genes we inherited at birth.

To date, 80 genes have been identified that contribute to the risk of dementia. These include genes such as ABCA7, TREM2, and SORL1. Carrying variants in these genes increases our chances of developing the disease by 2 to 3 times, or up to 8 times if we carry two copies of the well-known APOE gene in its E4 isoform (different forms of the same protein).

But even if you carry variants in the 80 known genes, 35% of the disease is still due to a complex interaction between our genes and our environment. In fact, there is great interest in studying these individuals with a high genetic burden who reach advanced ages with their cognitive abilities intact.

Thus, it is estimated that up to 45% of dementia cases could be prevented or delayed by modifying habits, even in people with a genetic predisposition. These good habits start at an early age, promoting a well-rounded education, as it has been found that a low level of education in childhood leads to lower “cognitive reserve,” which increases vulnerability to brain deterioration.

Keeping an active mind and an active social life are essential for delaying cognitive decline and avoiding depressive disorders, which contribute 3% to the risk of dementia. Likewise, maintaining a balanced diet and exercising regularly to control obesity, cholesterol, hypertension, and diabetes are key to maintaining good neuronal health. It is estimated that high cholesterol levels contribute 7% to the risk of dementia.

Another 7% of the risk comes from a combination of excessive alcohol consumption (more than two glasses of wine a day, approximately), smoking, or exposure to environmental pollution. Finally, it is essential to treat hearing and vision loss, which contribute 7% and 2% respectively to the risk of dementia.

Therefore, although we cannot change our genes, we can influence how our brain ages through our environment and habits. Prevention begins long before the first symptoms appear and can make a difference in cognitive health throughout life.

Head of the Genomics Unit at Ace Alzheimer Center Barcelona