A new study suggests that dementia and some types of cancer may have protective effects against one another.
The study, published in the December 23, 2009, online issue of Neurology, the medical journal of the American Academy of Neurology, found white Alzheimer's patients are 69 percent less likely to develop some types of cancer. Cancer patients, on the other hand, had a 43 percent lower tendency to develop alzheimer’s disease. The lower rates, however, did not translate to minority groups.
Among minority study participants, the researchers found an opposite trend, but it was not statistically significant, the researchers noted.
"Discovering the links between these two conditions may help us better understand both diseases and open up avenues for possible treatments," said study author Catherine M. Roe, PhD, of Washington University School of Medicine in St. Louis, MO, and a member of the American Academy of Neurology.
Abnormal cellular behavior is reported to be the main contributor to both conditions. There was no link between alzheimer's and vascular dementia, however, suggesting that the association has to do with neurodegenerative factors. Vascular dementia is attributed to damage to the brain's blood supply.
"In alzheimer's disease, excessive cell death occurs, whereas cancer is characterized by excessive cell growth,” Dr. Roe said.
A number of previous studies have pointed to a similar relationship but were subject to usual limitations of early research. For example, the earlier research could not pin down if the cancer patients in the study were protected against alzheimer’s or if they simply did not live long enough to develop it.
For this study, researchers looked at a group of 3,020 people age 65 and older who were enrolled in the Cardiovascular Health Study and followed them for an average of five years to see whether they developed dementia and an average of eight years to see whether they developed cancer. At the start of the study, 164 people (5.4 percent) already had alzheimer's disease and 522 people (17.3 percent) already had a cancer diagnosis.