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
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