The study found an association, but it did not prove that either disease creates a reduced risk of developing the other.
However, it’s possible that the two diseases result from opposite biological mechanisms, which lower the risk of the second disease in a person who already has the first, the researchers said. They noted that Alzheimer’s disease results from the death of brain cells, while cancer results from uncontrolled cellular growth and resistance to cell death.
The researchers analyzed information from more than 204,000 people age 60 and older in Italy. During the six-year study, 21,451 of the participants received diagnoses of cancer and 2,832 were found to have Alzheimer’s disease.
Those numbers include 161 people who were given diagnoses of both diseases. But the researchers calculated that 246 people with cancer ordinarily would have developed Alzheimer’s disease and 281 people with Alzheimer’s disease would have developed cancer, based on the prevalence of both diseases among people of the same age and sex as the study’s participants.
So in both cases, the risk of the second disease was reduced.
People who eventually developed Alzheimer’s disease had a lower risk of cancer both before and after their Alzheimer’s diagnosis, and people with cancer had a lower risk of Alzheimer’s disease both before and after their cancer diagnosis. This means that the diagnosis of the first disease did not appear to interfere with the diagnosis of the second disease, the researchers said.
The study did not take into account lifestyle factors such as smoking, physical activity and diet, which may influence the risk of these diseases.
— Live Science
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