[Risk factors for Alzheimer's disease]

Alzheimer disease (AD) is the most common cause of dementia in elderly patients. Identification of risk factors for AD would contribute to the understanding of AD pathogenesis and thus, help in the development of preventive methods. Early-onset familial AD is associated with mutations of the genes encoding amyloid precursor protein (APP), presenilin 1 (PS-1), or PS-2, resulting in the overproduction of amyloid beta-protein. Epidemiological and case-control studies have led to the identification of several risk factors for sporadic AD. The most concrete genetic risk factor for AD is the epsilon4 allele of apolipoprotein E gene (APOE). In addition, several genes such as CTNNA3, GAB2, PVRL2, TOMM40, and APOC1 are known to be the risk factors that contribute to AD pathogenesis. On the other hand, nongenetic risk factors, such as age, sex, alcohol consumption, smoking, depression, head injury, and nutrition have also been reported. Although aging is the strongest risk factor for AD, the mechanisms underlying the development of AD as a result of ageing remain to be elucidated.