People with Alzheimer's disease have a lower risk of cancer
than other elderly adults, a new study suggests. Additionally,
researchers found that seniors who were diagnosed with cancer were also less likely
to develop Alzheimer's.
Researchers said there are a number of genes that affect
both neurology and cancer growth - and pathways by which the two are connected
- that could explain the "unexpected" inverse link between the
diseases. "Cancer and Alzheimer's have been viewed by researchers as
completely separate," said Dr Massimo Musicco, who led the study at the
National Research Council of Italy's Institute of Biomedical Technologies in
"Some of the knowledge that we have on cancer can be
used for a better understanding of what happens when a person has Alzheimer's
disease, and vice versa," he said. There is convincing data that
Parkinson's disease is tied to a lower risk of cancer, said Dr Jane Driver, who
studies aging at Brigham and Women's Hospital in Boston.
More recently, the same pattern has been showing up for
other neurological disorders, including schizophrenia and Alzheimer's, she
But earlier studies haven't been able to rule out whether
Alzheimer's disease might be keeping cancer symptoms from being noticed - or
vice versa - or if people who die from one disease just have less time to be
diagnosed with the other.
What the study found
In their study, Musicco and his colleagues found people who
ultimately were diagnosed with Alzheimer's had a lower risk of cancer both
leading up to and after their diagnosis. Likewise those with cancer were less
likely to get Alzheimer's both before and after the cancer was caught.
"I'm hoping this will then convince all the doubters
that there is a true inverse association between Alzheimer's, Parkinson's and
probably some other neurologic diseases and cancer," Driver said. Musicco and his team tracked new cancer and Alzheimer's diagnoses among
204000 people age 60 and older living in Northern Italy. Between 2004 and
2009, just over 21000 of them were diagnosed with cancer and close to 3000
with Alzheimer's disease.
There were 161 people diagnosed with both diseases. The
researchers calculated that 246 cases of Alzheimer's disease would be expected
in members of the cancer group, based on their age and gender balance, and 281
cancers would be predicted among those with Alzheimer’s.
The lower rates meant
that people with cancer were 35% less likely to develop Alzheimer's disease
than other adults, the researchers wrote in the journal Neurology. And those with
Alzheimer's had a 43% lower risk of cancer.
The link held up when they looked at most cancers
individually. "These two diseases seem intrinsically related to human
aging," Musicco said."Cancer may be conceptualised as
a high tendency of cells to reproduce, which is so high that it is no [longer]
controlled," he said.
disease is exactly the reverse. It's a sort of incapacity of neuron cells to
reproduce."The study doesn't prove one disease is protective against the
other. It also doesn't mean people with Alzheimer's or cancers never have to
worry about getting the other condition, Driver said.
The researchers noted that they couldn't take into account
people's lifestyle and whether some habits might affect the risk of cancer and
Alzheimer's differently. Driver said the inverse link has "prompted
thinking outside the box" regarding ways to treat Alzheimer's disease -
for which good treatment options are scarce
"By further investigating this
decreased risk, there's a good chance we'll be able to find completely new
therapies," Driver said. "Any new lead or any new avenue to go down,
we really need to take it."