The study involved a group of 3,020 people aged 65 and older who were enrolled in the Cardiovascular Health Study.    In the study, researchers at Washington University School of Medicine followed the participants for an average of five years to see whether they developed dementia and an average of eight years to see whether they developed cancer.

At the start of the study, 164 people (5.4 percent) already had Alzheimer's disease and 522 people (17.3 percent) already had a cancer diagnosis. During the study, 478 people developed dementia and 376 people developed invasive cancer.     The findings showed that for people who had Alzheimer's disease at the start of the study, the risk of future cancer hospitalization was reduced by 69 percent compared to those who did not have Alzheimer's disease when the study started. For Caucasian people who had cancer when the study started, their risk of developing Alzheimer's disease was reduced by 43 percent compared to people who did not have cancer at the start of the study, although that finding was not evident in minority groups.

The researchers came to the conclusion that people who have Alzheimer's disease may be less likely to develop cancer, and people who have cancer may be less likely to develop Alzheimer's disease. 

"Discovering the links between these two conditions may help us better understand both diseases and open up avenues for possible treatments," said study author Catherine M. Roe, PhD, of Washington University School of Medicine and a member of the American Academy of Neurology (AAN).

The study findings were published in the December issue of Neurology, the medical journal of the AAN.