A common prostate cancer treatment that lowers testosterone can double the chances of men developing dementia, research has shown.
Androgen Deprivation Therapy (ADT) shuts down the body’s main supply of the male hormone and is a less drastic alternative to physical castration.
It is a standard treatment for men whose cancers have started to spread and cannot be eliminated by surgery or radiotherapy alone.
But a new study suggests there may be a serious hidden danger associated with ADT – an increased risk of Alzheimer’s and other forms of dementia.
Scientists who analysed the health records of more than 9,000 patients found that when men were given ADT their chances of having dementia within five years doubled.
In absolute terms, the risk is still small. Of the 1,829 patients who underwent androgen deprivation, just 7.9% developed dementia. This compared with 3.5% of the group not treated with ADT.
However, lead researcher Dr Nigam Shah, from Stanford University in the US, said: “The risk is real, and depending on the prior dementia history of the patient, we may want to consider alternative treatment.”
Men aged 70 and older, and who had been on ADT for at least 12 months, were most at risk, the study reported in the journal Jama Oncology showed.
The most common form of ADT used in the UK is a drug called goserelin, sold under the brand name Zoladex, which is injected.
It interferes with signals from the brain that instruct the testicles to make testosterone.
The scientists urged prostate cancer patients receiving ADT not to change their treatment without consulting their doctors.
Co-author Dr Kevin Nead, from the University of Pennsylvania, US, said: “I was surprised at how ubiquitous the effects on all types of dementia were, but I would definitely not alter clinical care based on our results.”
He said more research was needed to look at the link between ADT and dementia and identify what kinds of patients might be most at risk.
Male hormones are known to play a role in the health and growth of neurons, which may help explain the association, said the scientists.
Another type of treatment blocks the action of testosterone on tumours rather than cutting off supplies of the hormone.
There is no suggestion that taking these drugs, known as anti-androgens, increases the risk of dementia.