Exposure to toxins is one of the four “threats” that individuals need to avoid if they want to protect brain function. In terms of brain health, current wisdom is that if you don’t smoke, never start and if you do smoke, stop. This has been validated by a study sponsored by Kaiser Permanente and published in the Archives of Internal Medicine. It found that smoking elevates the risk of both Alzheimer's disease and vascular dementia. The study involved more than 20,000 ethnically diverse men and women. Results showed: a 157 percent heightened risk of Alzheimer's disease in people who had smoked more than two packs of cigarettes a day; and a 172 percent increased risk for vascular dementia, the second most common form of dementia. Researchers say the association between smoking and various forms of dementia is strong, but they do not know the exact reason. It has been shown before that people who smoke are more likely to have hypertension high blood pressure) and cerebral vascular disease, as well as inflammation, and may contribute to the damage of brain blood vessels and cells.