They found grade 1 level evidence in favour of a protective effect for the female hormone oestrogen,cholesterol lowering drugs (statins), drugs to lower high blood pressure, and anti-inflammatory drugs (NSAIDs).
They found the same level of evidence for folate, vitamins C and E, and coffee, all of which were associated with helping to stave off the disease.
Similarly, the pooled data indicated a strong association between high levels of homocysteine - an amino acid manufactured in the body - and depression and a significantly heightened risk of developing Alzheimer's disease.
The evidence also strongly pointed to the complex roles of pre-existing conditions as either heightening or lowering the risk.
The factors associated with a heightened risk included frailty, carotid artery narrowing, high and low blood pressure, and type 2 diabetes (in the Asian population). Those associated with a lowered risk included a history of arthritis, heart disease, metabolic syndrome, and cancer.