A Slight Comfort for Former Cancer Patients

In February I posted a blog about three conditions where a particular disease or condition was associated with a reduced risk of another specific disease developing. Now here’s another example.  A history of cancer is associated with a reduced risk of Alzheimer’s.  (But remember ‘associated with’ is not a cause-and-effect relationship!) There have been previous reports of an association.  Thus people with Alzheimer’s have been shown to have half the risk of developing cancer as those without Alzheimer’s, and those with Alzheimer’s have a reduced risk of getting cancer.  A report just given at the American Academy of Neurology meeting consisted of an analysis of data from the Framingham Heart Study on survivors of cancer who survived at least 10 years, ruling out a ‘survivor bias’ problem that devilled the earlier study.

This analysis covered 655 Framingham subjects who were over 75 and free of dementia between 1986 and 1990. There were 130 verified cases of cancer among them.  All participants had Mini-Mental state exam tests for Alzheimer’s every 2 years since 1981. 

Over an average follow-up of 8 years, 175 cases of dementia (136 of them Alzheimer’s) were found among the cancer survivors.  The number of non-skin cancers in probable-plus-possible Alzheimer’s patients was about half that in non-Alzheimer’s subjects.  There was no such associated reduction for skin cancers. 

In the reverse analysis, the researchers found the same result as in the earlier study: subjects were less than half as likely to develop cancer if they had been diagnosed with Alzheimer’s disease. 

These results are rather similar to those reported for Parkinson’s disease, where patients also had a decreased risk of developing any cancer except melanoma, which was increased. In these cases, there seems to be involvement of melanin-producing cells, which are found, of course, in melanoma, but also in the affected area of the brain of Parkinson patients.  It’s from such clues as these that progress may be expected in discovering the causation of Alzheimer’s, cancers, melanoma, and Parkinson’s disease.  For the patients, there’s just the consolation of a reduced risk of another serious condition developing . . .