Patients with Alzheimer’s disease have a lower risk of developing cancer, while seniors with cancer have lower rates of Alzheimer’s disease compared to cancer-free people of the same age, researchers from the National Research Council of Italy, Milan, reported in the journal Neurology.

Study author, Dr. Massimo Musicco, explained that as the numbers of cancer and Alzheimer’s cases grow more and more rapidly, “people age, understanding the mechanisms behind this relationship may help us better develop new treatments for both diseases.”

Dr. Musicco and colleagues gathered and analyzed data on 204,468 northern Italian citizens over a six-year period (2004-2009); they were all aged 60+ years. Over that period 2,832 of them developed Alzheimer’s disease and 21,451 developed cancer.

However, only 161 developed both Alzheimer’s and cancer; the researchers had expected the number to be much higher. When considering how often cancer and Alzheimer’s occur in the general population, they had expected there to have been 281 cases for cancer and 246 for Alzheimer’s.

The team found that:

  • Alzheimer’s patients were half as likely to develop cancer.
  • Cancer patients were 35% less likely to develop Alzheimer’s.

Dr. Musicco said:

While other studies have noted this relationship before, this is the largest study to date and it has several strengths over previous studies, such as looking for the presence of the second disease both before and after the first disease was diagnosed.

This controls for the possibility that the presence of one disease might obscure the diagnosis of other diseases because any new symptoms might be interpreted as a consequence of the already-diagnosed disease, or in the case of cancer, people might assume that memory problems were a side effect of chemotherapy.”

Figures were proportionally the same for people who died during the six-year study period as those still alive, which ruled out the possibility that lower life-expectancy for the first disease might explain the lower risk of developing the second.

The study was sponsored by the National Research Council of Italy and the Foundation IRCCS “Santa Lucia”, Rome.

In 2009, researchers from Washington University School of Medicine in St Louis, Missouri, USA, reported in the same journal that Alzheimer’s and cancer are much less likely to occur simultaneously. Study leader, Dr Catherine M. Roe, said “If there truly is an inverse association, it gives us one more way of finding out what’s going wrong in both cancer and Alzheimer’s, and that could lead us to new ways to treat either condition.”

Alzheimer’s is not the only neurodegenerative disease that appears to reduce cancer risk. A study conducted at the University of British Columbia and Vancouver Coastal Health found that people with MS (multiple sclerosis) were less likely to develop cancer. The study was published in the journal Brain. Lead author, Elaine Kingwell, said “Because the immune system plays important roles in both cancer and MS, we wanted to know whether the risk of cancer is different for people with MS. Not only did MS patients have a lower overall cancer risk, the risk for colorectal cancer in particular was significantly lower.”

Written by Christian Nordqvist