Dec. 23, 2009 -- Having Alzheimer’s disease just may convey some protection against cancer, and vice versa, early research suggests.
Elderly whites with cancer at the beginning of the study were less likely to develop Alzheimer’s disease over five years of follow-up, but the lower risk was not seen in other groups.
Several previous studies have shown a lower incidence of cancer in patients with Parkinson’s disease, which, like Alzheimer’s, is a degenerative disorder affecting the brain.
The newly published research suggests a similar link between cancer and Alzheimer’s disease.
“This study adds to the literature suggesting that cancer and neurodegenerative diseases may be related,” lead researcher Catherine M. Roe, PhD, of Washington University School of Medicine in St. Louis, tells WebMD.
Alzheimer’s Patients Get Cancer Later
In an earlier study, Roe and colleagues reported that elderly patients with Alzheimer’s developed cancer later than patients without dementia. Patients with a history of cancer also tended to be diagnosed with dementia later in life.
But it was not clear if the association was because of confounding factors, such as the fact that cancer patients often die before they reach the high-risk age for Alzheimer’s disease and Alzheimer’s patients tend to be screened less aggressively for cancer.
In their newly published study, Roe and colleagues attempted to control for many of these potential confounders.
The study included patients with Alzheimer’s disease, caused by loss of nerve cells within the brain, and vascular dementia, caused by impaired blood flow to the brain as a result of stroke and other cardiovascular causes. Alzheimer’s disease is the most common type of dementia and vascular dementia is the second most common type.
About 3,000 people aged 65 and older enrolled in a large heart health study were included in the analysis.
Alzheimer's Patients Had 69% Lower Cancer Risk
Having vascular dementia at the start of the study appeared to have no impact on hospitalization for cancer over eight years of follow-up.
But compared to people without Alzheimer’s, patients with Alzheimer’s disease at study entry were 69% less likely to be hospitalized with cancer during the same time period.
The risk of developing Alzheimer’s disease was reduced by 43% in white patients with a history of cancer, compared to participants without cancer, but the finding did not hold for other racial and ethnic groups.
The study appears online and in the Jan. 12 issue of the journal Neurology.
Roe says more research is needed to determine if cancer and degenerative brain diseases like Alzheimer’s and Parkinson’s really are related.
“We are in the beginning stages of this research,” she says. “There is a lot to be done before concluding that a link exists.”
Alzheimer’s disease specialist David Knopman, MD, agrees, but says his own clinical experience makes him think something is going on.
Knopman is a professor of neurology and a member of the Alzheimer’s Disease Research Center at the Mayo Clinic in Rochester, Minn.
“I see (Alzheimer’s) patients for four, five, and six years at an age when cancer is common, and they just don’t seem to die of cancer as often as other patients,” he says. “If there are shared genetic factors at work in cancer and Alzheimer’s disease, the Alzheimer’s community may be able to learn from cancer research and the cancer community can learn from Alzheimer’s.”