Men taking androgen deprivation therapy (ADT) for prostate cancer were almost twice as likely to be diagnosed with Alzheimer’s disease in the years that followed than those who didn’t undergo the therapy, an analysis of medical records from two large hospital systems by Penn Medicine and Stanford University researchers has shown. Men with the longest durations of ADT were even more likely to be diagnosed with Alzheimer’s disease.

The findings, published in the December 7 issue of the Journal of Clinical Oncology, do not prove that ADT increases the risk of Alzheimer’s disease. But the authors say they clearly point to that possibility, and are consistent with other evidence that low levels of testosterone may weaken the aging brain’s resistance to Alzheimer’s.

“We wanted to contribute to the discussion regarding the relative risks and benefits of ADT, and no one had yet looked at the association between ADT and Alzheimer’s disease,” said lead author Kevin T. Nead, MD, MPhil, a resident in the department of Radiation Oncology at the Perelman School of Medicine at the University of Pennsylvania, and a fellow at Penn’s Leonard Davis Institute of Health Economics. “Based on the results of our study, an increased risk of Alzheimer’s disease is a potential adverse effect of ADT, but further research is needed before considering changes to clinical practice.” 

Nigam Shah, MBBS, PhD, associate professor of biomedical informatics research at Stanford, served as senior author. Samuel Swisher-McClure, MD, MSHP, an assistant professor of Radiation Oncology at Penn Medicine, served as a co-author.

Androgens (male hormones) normally play a key role in stimulating prostate cell growth. Thus, therapies that suppress androgen production or activity are often used in treating prostate tumors. In the U.S. alone, about half a million men are taking ADT at any given time.

Drastically reducing androgen activity can have adverse side-effects, however. Studies have found associations between low androgen levels (chiefly low testosterone levels) and impotence, obesity, diabetes, high blood pressure, heart disease, and depression. Research in recent years also has linked low testosterone to cognitive deficits, and has shown that men with Alzheimer’s tend to have lower testosterone levels, compared to men of the same age who don’t have the disease.

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