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Prostate cancer: hormone therapy may raise risk of Alzheimer's, dementia

For patients with prostate cancer, treating the disease with androgen deprivation therapy ( ADT ) is linked to a higher likelihood of being diagnosed with Alzheimer's disease or dementia, compared to patients who do not receive the therapy, according to a study from researchers in the Perelman School of Medicine at the University of Pennsylvania.
The results were published in JAMA ( Journal of the American Medical Association ).

Of the 154,089 men sampled in the study, 62,330 received androgen deprivation therapy within two years of their prostate cancer diagnosis and 91,759 did not.
Of the patients with prostate cancer who received the hormone therapy, 13% were later diagnosed with Alzheimer's disease, compared to 9% who did not receive ADT.
For dementia, those numbers widened: 22% of prostate cancer patients who received androgen deprivation therapy were diagnosed with dementia, compared to 16% who did not receive the therapy.

This research builds on previous, smaller studies which showed similar correlations between hormone therapy and cognitive risks in patients with prostate cancer.
The lifetime risk for Alzheimer's dementia for men overall is 12%, according to data from the Framingham Heart Study.

Prostate cancer is the most commonly diagnosed non-skin cancer in the United States and the second leading cause of cancer death in American men.
Androgen deprivation therapy, or hormone therapy, has been shown to dramatically reduce the spread and progression of the disease.
The treatment works by reducing levels of male hormones in the body, called androgens, to stop them from stimulating prostate cancer cells to grow.
It is typically used in patients who have an advanced state of the disease, when the cancer has metastasized, or in those with a high risk of recurrence after their initial treatment.

Despite the benefits of androgen deprivation therapy, its use has faced controversy, as some evidence suggests that decreasing androgen levels may increase risk factors for Alzheimer's and dementia, including loss of lean body mass, diabetes mellitus, cardiovascular disease, and depression.
Hormone therapy may also affect cognitive function by impairing neuron growth and the regeneration of axons.

After controlling for several factors, such as other medical conditions, disease severity and sociodemographic characteristics ( like age and marital status ) the Penn researchers determined the hazard ratio ( HR ) for prostate cancer patients who receive hormone therapy.
A hazard ratio measures the effect of an intervention over time.
With all other factors remaining equal, the research team determined that patients with prostate cancer who receive hormone therapy face a hazard ratio that translate to a 14% increased risk of developing Alzheimer's and a 20% increased risk of dementia, when compared to other prostate cancer patients who are not exposed to androgen deprivation therapy.

The Penn study contrasts with results from several recent papers that have examined the association ( or lack thereof ) between androgen deprivation therapy and dementia.
These past studies relied on data from a single institution, while others fail to adjust for cancer stage, ADT dose, and duration.
Many examined a small cohort of patients and only for a short amount of time following their treatment.

By contrast, the Penn study used data from the Surveillance, Epidemiology, and End Results ( SEER ) - Medicare linked database of the National Cancer Institute ( NCI ), which brings together Medicare administrative claims data and clinical tumor registry data from 18 different sites, encompassing 28% of the U.S. population.
For their retrospective study, the Penn researchers collected data from a sample of men ages 66 years and older with localized or advanced prostate cancer who were diagnosed between 1996 and 2003.

The team noted more research is necessary to understand the possible biological mechanisms that underlie the link between dementia and androgen deprivation therapy.

Source: Perelman School of Medicine at University of Pennsylvania, 2019