A recent Italian study finds that there seems to be an inverse relationship between cancer and Alzheimer’s.

The study—with 25,000 subjects from Milan—found that people diagnosed with cancer had a 35% decreased risk of being diagnosed with Alzheimer’s and that those diagnosed with Alzheimer’s had a 43% decreased risk of being diagnosed with cancer.

Scientists are not yet sure of the reason cancer and Alzheimer’s have an inverse correlation, but speculate that it is a difference in genes and not because, as was a previously-held belief, that having one disease reduced a person’s lifespan and therefore could not develop the other disease.

Dr. Jane A. Driver, an epidemiologist, oncologist, and geriatrician at the VA Boston Health System and Brigham and Women’s Hospital, explains that the diseases are caused by opposing genetic activity. Cancer causes cells to develop, multiply, and not die; whereas Alzheimer’s brain cells die and cannot be replaced.

Dr. Driver is in the stages of developing a drug to work with the gene PIN1, which is believed to be involved in both diseases.

One thing that this study shows scientists they need to be wary of is that if they find a drug to treat one of the diseases, will it then cause the other disease to develop?

This study was published in the journal, Neurology, just ahead of the Alzheimer’s Association International Conference, beginning this weekend in Boston. This is sure to be among the hottest topics at the conference.