Indeed, cancer patients appeared more likely to experience stroke, osteoarthritis or eye problems, such as cataracts. The majority of cancer patients also appeared to face a higher risk for forms of dementia other than Alzheimer's.
In terms of cancer treatments, undergoing radiation was not linked to reduced Alzheimer's risk. But undergoing chemotherapy lined up with a drop in Alzheimer's risk ranging from 20 percent to 45 percent.
Frain said the research team is now investigating which chemotherapy drugs are associated with a lower risk of Alzheimer's disease.
[Read: Fight These 4 Causes of Aging.]
"The benefit of investigating this unusual, inverse relationship between cancer and [Alzheimer's] may be a better understanding of both diseases and, importantly, the chance to find novel therapies, if drugs can be designed to specifically target one disease without increasing the risk of the other," Frain said.
The study was hailed by Dr. James Galvin, a professor of neurology, psychiatry, nursing and nutrition at NYU Langone School of Medicine in New York City.
"These findings are very important in light of recent studies of mouse models of [Alzheimer's] that showed possibly significant treatment effects on [Alzheimer's] pathology by a number of chemotherapeutic drugs, particularly those used to treat blood-related cancers [and] lung and liver cancers," Galvin said.
Dr. Catherine Roe, an instructor in neurology at Washington University School of Medicine in St. Louis, seconded the thought.
"If other scientists also find that chemotherapy is associated with a reduced risk of Alzheimer's disease, then it would be a good sign that we may be able to come up with a treatment that is effective in preventing Alzheimer's disease in the future," she said.
The data and conclusions of research presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.
For more on Alzheimer's, visit the U.S. National Institutes of Health.
Copyright © 2012 HealthDay. All rights reserved.