Many of the environmental risk factors associated with Alzheimer's disease, including infectious agents (herpes simplex, chlamydia pneumonia, and Borrelia burgdorferi) as well as Vitamin A deficiency, hypercholesterolaemia, hyperhomocysteinaemia or folate deficiency, oestrogen depletion, cerebral nerve growth factor (NGF) deprivation, diabetes, cerebral hypoperfusion (leading to hypoxia and hypoglycaemia) or are able to promote cerebral beta-amyloid deposition (in the absence of any particular gene variant) in animal models [1]. Here, NGF is linked to Alzheimer disease.