Alzheimer's and Cancer May Protect Against Each Other: A Study

Alzheimer's disease appears to protect against cancer and vice versa, a new paper published in the medical journal of the American Academy of Neurology reports.

As the largest study of its kind, researchers from the National Research Council of Italy in Milan found that people with Alzheimer's disease were 43 percent less likely to develop cancer while people with cancer were 35 percent less likely to develop Alzheimer's disease when compared with the general population.

In all, researchers looked at information from 204,000 people 60 years old and older in Italy over a six year period.

During the study, 21,451 people were diagnosed with cancer and 2,832 were diagnosed with Alzheimer's disease - including 161 people who were diagnosed with both diseases.

Statistically speaking, however, this number was significantly lower than the researchers expected: in all, 246 people with cancer would have developed Alzheimer's disease, and 281 people with Alzheimer's disease would have developed cancer among the same demographics normally given the prevalence of both diseases.

Though, the researchers did note that the study did not take into account lifestyle factors, such as smoking, physical activity and diet, which may influence the risk of these diseases.

Such findings corroborate those of earlier studies, which also demonstrate a lower risk of cancer for people with Alzheimer's disease and the reverse; however, while these studies have found associations, none of them can prove that either disease is responsible for reducing the risk of the other.

One possibility, however, is that the two diseases result from opposite biological mechanisms that consequently reduce the chances of one another. For example, the researchers noted that Alzheimer's disease results from the death of brain cells while cancer results from out-of-control cellular growth as well as cell death.

Should future studies confirm the findings, Catherine Roe of Washington University School of Medicine, St. Louis, is convinced that this relationship could aid researchers in treating the diseases.

"This knowledge may help in gaining a better understanding of and developing new treatments for both diseases," Roe wrote in an editorial accompanying the study.