Cancer and Alzheimer's: A Less Likely Duo

Alzheimers and cancer at once may not be as big a risk for older people

(RxWiki News) Alzheimer's disease and cancer are big concerns for many aging people. Having one of those conditions can be difficult for patients and families. Having both would likely be an even greater hardship.

According to new research, however, there is an inverse relationship between cancer and Alzheimer's disease.

The study found that older people with cancer are less likely to also have Alzheimer's disease, and people with Alzheimer's disease are less likely to also have cancer.

"Ask your doctor about staying healthy as you age."

Massimo Musicco, MD, PhD, of the National Research Council of Italy in Milan, was the study's lead author.

From 2004 through 2009, Dr. Musicco and his fellow researchers tracked the health of 204,468 northern Italian men and women who were at least 60 years old. 

During those six years of being monitored by researchers, 21,451 of the study participants developed cancer. The number who developed Alzheimer's was 2,832. The number of individuals developing both cancer and Alzheimer's was 161. 

Considering how often the two diseases generally develop among northern Italians aged 60 and older, the researchers had expected more people to have both Alzheimer's and cancer at the same time.

These researchers wrote that they expected 281 people who first were diagnosed with Alzheimer's to later develop cancer. They also expected that 246 people who were first diagnosed with cancer would later develop Alzheimer's.

What they found, instead, was that people with Alzheimer's disease were about half as likely as the overall population of northern Italians to later be diagnosed with cancer. People with cancer were 35 percent less likely to also develop Alzheimer's than the overall population of northern Italians.

The researchers found that these reduced risks held true even in people who died during the six years of the study.

Carla Perissinotto, MD, MHS, a University of California at San Francisco geriatric specialist, gave dailyRX her view of the study: It's "...most important ... to the think about the implications of both of these diagnoses on health. Both affect life expectancy and an individual's function. Also, once an individual has a diagnosis of Alzheimer’s, their life expectancy is limited. Often, it no longer makes sense to screen for cancers [or] pursue aggressive treatments [for] an individual with dementia [who] will have a harder time coping with aggressive treatments and hospitalizations."

To support their findings, this study's researchers wrote that they checked for the presence of the second disease before and after the first disease was diagnosed.

"This [helped eliminate] 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," Dr. Musicco said in a press statement.

He continued, "Since the number of cases of both Alzheimer's disease and cancer increase exponentially as people age, understanding the mechanisms behind this relationship may help us better develop new treatments for both diseases." 

Ninety percent of the study's cancer patients had either prostate, colon, lung or urinary bladder cancers. The remainder had other types of cancer. People with forms of dementia other than Alzheimer's, which is the most common form of dementia, were not included in the study.

While study participants were as young as 60, the average age of Alzheimer's patients in the study was 78.1 years. The average age for cancer patients was 72.4 years. 

Study participants aged 70 through 84 were the least likely to have both Alzheimer's and cancer at the same time. As that group continued to age, their risks for getting both diseases steadily declined.

Risks of having both diseases simultaneously began to rise again for those aged 85 and older. Risks for having both diseases at once were highest among those aged 60 to 69.

This study was published July 10 in Neurology.

Three of the study's eight researchers reported that pharmaceutical companies had paid them for speaking engagements.

Review Date: 
June 30, 2013