head injury: Studies show that people who have suffered concussions are more likely to develop Alzheimer's later on.
vascular disease: Coexisting small strokes increase the risk and severity of memory problems in Alzheimer's disease.
inflammation: People with arthritis are less likely to get Alzheimer's. It is speculated that the medications used to reduce inflammation in arthritis may have a beneficial effect on an inflammatory process in the brain.
gender: Women are nearly twice as likely as men to suffer from Alzheimer's.
education: Research suggests that better educated people are less prone to Alzheimer's. Those who already have the disease do better if they keep mentally active - an unused brain may deteriorate faster.
toxins (e.g., aluminum): A controversial and unproven theory links aluminum in drinking water to senile plaque formation. Earlier studies hinted at a connection, but not according to recent studies that are larger and better-designed.
prions: Some scientists speculate that prions, tiny infectious particles made of protein, may be involved in Alzheimer's disease by infecting the brain.