Alzheimer’s disease (AD) is the most common form of dementia, accounting for 60–80% of all cases . It is currently considered incurable and it eventually leads to death. The progression of this disease is mostly one-directional with the average survival times after diagnosis lying around 7 years , and the probability of living longer than 14 years is smaller than 3% .
The recognized main risk factors of AD comprise, but are not limited to, high age, mild cognitive impairment, lack of social engagement, low level of education, family history, APOE allele ε4 genotype, and cardiovascular disease and traumatic brain injury . Although the age has been recognized as the strongest risk factor, alone it is not sufficient to cause the disease. A mild cognitive impairment can also be associated with AD, however, it does not always lead to this neurological disease and individuals can return to a normal condition instead [1,4–6]. Multiple studies have previously suggested that social and cognitive engagement supports brain health and leads to a reduced risk of AD [7–9]. Besides these environmental factors, the polymorphic allele ε4 of APOE, a major cholesterol carrier that supports injury repair in the brain, has been widely associated with AD, while the ε2 allele is considered to decrease the risk [10–12].