Environmental. Traumatic brain injury increases risk for major or mild NCD due to Alz heimer's disease.
Genetic and physiological. Age is the strongest risk factor for Alzheimer's disease. The genetic susceptibility polymorphism apolipoprotein E4 increases risk and decreases age at onset, pa rticularly in homozygous individuals. There are also extremely rare causative Alzheimer's disease genes. Individuals with Down's syndrome (trisomy 21) develop Alz heimer's disease if they survive to midlife. Multiple vascular risk factors influence risk for Alzheimer's disease and may act by increasing cerebrovascular pa thology or also through direct effects on Alzheimer pathology.