Diagnoses of Alzheimer’s or cancer are never good news, but they may come with a small silver lining.
Scientists have found that having Alzheimer’s reduces the risk for cancer, just as a diagnosis of cancer brings a reduced likelihood of developing the brain disorder.
In a study published online in Neurology Dec. 23, scientists report on results from more than 3,000 people, all at least 65 years old, enrolled in an extended survey of cardiovascular health. Those who entered the survey with Alzheimer’s had a 69 percent reduced chance to be hospitalized due to cancer. Those who had cancer at the outset were 43 percent less likely to develop Alzheimer’s, at least in Caucasians. (In other ethnic groups, the opposite seemed to hold true, although sample sizes were too small to provide reliable data in these populations.)
But no association was found between cancer and vascular dementia, the second most common form of dementia after Alzheimer’s. Unlike Alzheimer’s, which is characterized by abnormal proteins that lead to brain cell death, vascular dementia stems from clogged blood vessels that starve neurons of oxygen.
The reasons for these trends are not clear, since the study looked at overall health trends and was not designed to investigate causes. But the authors speculate that the findings imply that cancer and Alzheimer’s share some common molecular basis that vascular dementia does not.
Previous studies have also found links between cancer risks and neurological disorders. Parkinson’s patients, in particular, have a reduced risk for many cancers; one possible cause, scientists think, is that Parkinson’s causes increased apoptosis—or programmed cell “suicide”—throughout the body, stifling many cancers before they have a chance to establish themselves.