A second group of researchers recently demonstrated that cancer patients have a lower risk of Alzheimer's disease, providing data that adds to the puzzling nature of this finding:
[Researchers] found that most types of cancer were associated with a reduced risk of Alzheimer's, which has no cure. Survivors of liver cancer had the most protection, a 51 percent reduced risk. Cancers of the pancreas, esophagus, lung, and kidney, as well as leukemia, also appeared to be "protective," reducing risk between 22 and 44 percent. The study, released just days after publication of a similar report from Italian researchers, is by far the largest to establish such a link.
Notably, the researchers also found that certain cancers apparently conferred no reduced Alzheimer's risk, including melanoma (a cancer of the skin), prostate, and colorectal cancers. Breast cancer was not studied because there were too few cases in the database the researchers analyzed of nearly 3.5 million veterans, 98 percent of them men, who received care between 1996 and 2011.
The scientists said the reduced risk of Alzheimer's was not simply because cancer patients die young, before they can develop the dementia. Cancer survivors lived long enough and even appeared to be at increased risk to develop other typical age-related diseases, including stroke, osteoarthritis, cataracts, and macular degeneration. And they found that most cancer survivors also had an increased risk for non-Alzheimer's dementia. The protective effect of most cancers seemed to extend only to Alzheimer's. [What] surprised the team was the other finding: Cancer patients treated with chemotherapy enjoyed a reduced Alzheimer's risk. They were 20 to 45 percent less likely to develop Alzheimer's than cancer survivors who were not treated with chemotherapy.