When a man is diagnosed with prostate cancer, treating the disease is his first priority. But when the treatment can increase risk for Alzheimer’s disease and other forms of dementia, the decision-making becomes much more complicated.

While a variety of treatments are available for prostate cancer, a hormone therapy known as androgen deprivation therapy (ADT) can be particularly lifesaving in men with metastatic prostate cancer that has spread to other parts of the body. But at what cost?

Previous research looking at an association between ADT and dementia has yielded mixed results. So researchers wanted to get a clearer picture of ADT, which slows or halts the progression of prostate cancer by depriving the cancer cells of the fuel (androgen) that stimulates their growth.

Study details: More than 154,000 men (age 66 and older) with localized or advanced prostate cancer were tracked for an average of eight years after their diagnosis—about 62,000 of them got ADT within two years of their prostate cancer diagnosis, and approximately 92,000 did not. Men in both groups may also have received surgery, radiation and/or chemotherapy for their prostate cancer.

Results: Among the men who had been treated with ADT, 13% developed Alzheimer’s disease compared with 9% of the men who did not get ADT, according to the study findings that were published in JAMA Network Open. The numbers were even higher when the researchers looked at how many of these men developed some other form of dementia—22% of those who got ADT versus 16% who had not received the hormone treatment.

Why this research matters: This was the longest and largest study of its kind to find an association between ADT and these cognitive diseases. The researchers note that more studies are needed to uncover the possible biological mechanisms that may explain the link between dementia and ADT.

Takeaway: Even though ADT can save lives, a higher risk for Alzheimer’s disease and dementia can be added to the list of ADT’s other possible side effects, which include diminished libido, thinner bones, loss of muscle mass, hot flashes and an increased risk for cardiovascular disease.

For this reason, the severity of a man’s prostate cancer should be considered when evaluating the use of ADT. For example, men with localized prostate cancer may want to choose a different treatment, such as surgery, radiation and/or chemotherapy…or even an active surveillance protocol, in which the patient is closely monitored and treated only if his cancer progresses. All men with prostate cancer should work closely with their doctors to identify the best treatment options based on the specifics of their disease.