Elderly patients with Alzheimer's less likely to develop cancer -- and vice versa

A new study published in the medical journal of the American Academy of Neurology has found that older people with Alzheimer's disease are less likely to develop cancer.  The same study also showed the reverse to be true, indicating that older people with cancer are less likely to develop Alzheimer's disease.

"Since the number of cases of both Alzheimer's disease and cancer increase exponentially as people age, understanding the mechanisms behind this relationship may help us better develop new treatments for both diseases," said the study author Dr. Massimo Musicco, of the National Research Council in Milan, Italy.

Previous studies have examined the possible relationship between Alzheimer’s and cancer in old age, but Musicco said the studies did not utilize enough research subjects.

“All the papers reported a negative association between the two diseases, but the number of people being studied was quite small,” he said.

Looking to use a larger group of people for observation, Musicco analyzed a population of 204,468 people in northern Italy aged 60 and over during a six-year period. Over the course of that time, 21,451 people developed cancer and 2,832 people developed Alzheimer's disease.

The results showed that a total of 161 people had both cancer and Alzheimer’s disease.

Based on how frequently these diseases develop in the general population, that number would have been expected to be 281 for cancer and 146 for Alzheimer’s disease. Instead, the risk of cancer was significantly reduced by half for people with Alzheimer's disease, while the risk of Alzheimer's disease for people with cancer decreased by 35 percent.

Musicco believes this study will benefit future populations of people by diving further into the genetic diversities between these two prominent diseases.  He hopes future research can potentially explain the protective quality these diseases may have against one another.

“This is a real problem in our society,” Musicco said.  “In Italy, near one-fourth of the population is at 65 or older, so we have further justification to intervene against cancer and Alzheimer’s. This will be key. By balancing the two diseases, this might be sort of a new view about them. No interest like this has existed before.”