Coffee, in excess is traditionally considered to be unhealthy, as it can lead to irritability, dehydration, and a jump in blood pressure. According to a study released in the Journal of Alzheimer's Disease however, drinking three to five cups a day has shown to reduce the risk of contracting Alzheimer's disease by as much as 65%.
The Cardiovascular Risk Factors, Aging and Dementia study, a Finnish study started in 1972, found that of the 1409 people who were available to complete the twenty-one year study, 48 ended up with Alzheimer's disease. Those who regularly drink more coffee (three to five cups), once they were around middle-age, had the most positive results. The researchers believe the promising data may have something to do with the way that caffeine acts on the central nervous system, having an overall stimulatory effect. Although tea contains caffeine as well, not enough subjects drank tea to be able to draw the same conclusions.
The hope is with the results of this study, which ended back in 1998, that there may be new ways to help prevent Alzheimer's disease with the knowledge of the impact of coffee consumption.