One possible cause of Alzheimer’s disease is a history of head injury causing a loss of consciousness. The link has been established in a study among elderly people.
Alzheimer’s disease was diagnosed in 39 of them, all of whom had suffered head injuries in the previous 30 years.
Researchers reckon that these injuries increase the risk of developing Alzheimer’s by 5.4 times (J Neurology, Neurosurgery and Psychiatry, 1997; 62: 119-24).