In a bit of good news for people with terrible diagnoses, having cancer appears
to protect against developing Alzheimer's disease, and vice versa.
What began as a hunch by a handful of researchers is confirmed in a study
published Wednesday in the journal Neurology. People diagnosed with Alzheimer's
were found to have a 43% lower risk of developing cancer than those without the
disease, and people with cancer ran a 35% lower chance of developing
Alzheimer's, according to the study of 25,000 residents of the city of Milan.
This inverse relationship between cancer and Alzheimer's will be one of the hot
topics at the Alzheimer's Association International Conference in Boston
beginning this weekend. It is expected to include more than 4,500 researchers
from 66 countries and cover subjects such as Alzheimer's risk factors, early
detection, imaging and treatment.
Alzheimer's is projected to triple over the next generation and become a huge
social and financial burden. People with Alzheimer's suffer loss of memory,
decreased thinking and language skills, and behavioral changes that can make
caregiving challenging. Current treatments do not address underlying symptoms or
stop progression of the fatal disease.
"Alzheimer's is a disease that is going to dwarf every other disease, in terms
of cost, in terms of effect on people's lives, and we're not as far ahead as we
should be," says Jane Driver, an epidemiologist, oncologist and geriatrician at
the VA Boston Healthcare System and Brigham and Women's Hospital.
No one knows why Alzheimer's and cancer are inversely related.
Massimo Musicco, lead author of the new paper, says he believes the two are
simply different facets of aging. If you have one set of genes, you are likely
to take one disease pathway as you age; another set will direct you along a
different route, he says.
Driver, who was not involved in the study but has led similar research, says the
two conditions are probably caused by opposite genetic activity. Cancer is
essentially a disease in which cells reproduce too much and refuse to die; in
Alzheimer's, brain cells die off too quickly. Driver is developing potential
drug candidates that increase or reduce activity of a gene, PIN1, which appears
to be involved in both diseases.
Not all cancers seem to offer the same protection against Alzheimer's. Prostate
cancer isn't protective, the latest study and other research says, though
scientists aren't sure why.
The study answers critics who had thought the relationship could be explained
simply: Someone with cancer or Alzheimer's might not live long enough to get the
other. Yet the cancer rate was lower for people later diagnosed with
Alzheimer's, and vice versa, Musicco says.
Catherine Roe of the Washington University School of Medicine says scientists
laughed at her in 2005 when her research first suggested a link between
Alzheimer's and cancer. Now, she says, more scientists will take the connection
seriously: "It could open avenues of investigation people haven't even thought
of yet. They've been looking at the usual suspects for so long."
Sebastien Bozon, AFP/Getty Images