July 11, 2013
Are Cancer And Alzheimer’s Disease Mutually Exclusive?
Brett Smith for redOrbit.com - Your Universe Online
The study, which was published in the journal Neurology, found that patients with Alzheimer's had a 43 percent lower risk of developing cancer than those without the neurological condition, and people with cancer had a 35 percent lower risk of developing Alzheimer's.
"Cancer and Alzheimer's have been viewed by researchers as completely separate," said study co-author Dr. Massimo Musicco, from the National Research Council of Italy's Institute of Biomedical Technologies in Milan.
"Some of the knowledge that we have on cancer can be used for a better understanding of what happens when a person has Alzheimer's disease, and vice versa," Musicco told Reuters.
Some previous studies have shown an association between neurological disorders, such as Parkinson's disease and schizophrenia, and lower cancer risk; but these studies haven't established if the cancer simply went unnoticed or undiagnosed.
"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," Musicco said. "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."
In the new study, the researchers tracked new cancer and Alzheimer's diagnoses for over 200,000 people ages 60 and older living in northern Italy. From 2004 to 2009, more than 21,000 of those in the study were diagnosed with cancer and approximately 3,000 with Alzheimer's disease. Over 160 people were diagnosed with both diseases.
The researchers determined that approximately 250 cancer patients should statistically be diagnosed with Alzheimer's and around 280 of those with Alzheimer's should also contract cancer. The lower actual rates suggested an inverse relationship between the two diseases.
"These two diseases seem intrinsically related to human aging," Musicco said.
"Cancer may be conceptualized as a high tendency of cells to reproduce, which is so high that it is no (longer) controlled," he explained. "Alzheimer's disease is exactly the reverse. It's a sort of incapacity of neuron cells to reproduce."
According to Dr. Jane Driver, who studies aging at Brigham and Women's Hospital in Boston and was not involved in the study, the results don't prove that one disease protects against the other and warned against people with one condition discounting the other.
For their part, the researchers said they weren't able to take lifestyle or other factors into account when reaching their findings.
Driver noted that the inverse relationship could prompt some "outside the box" thinking, which could lead to better treatments for both conditions.
"By further investigating this decreased risk, there's a good chance we'll be able to find completely new therapies," Driver told Reuters.