Researchers in the United States have linked male sterilization surgery to a certain form of dementia.
A team at Northwestern University in Illinois say men who have had a vasectomy may have an increased risk of developing a neurological condition called primary progressive aphasia, or PPA.
This rare type of dementia is characterised by a steady loss of language skills.
The researchers surveyed 47 men with the condition being treated at Northwestern's Cognitive Neurology and Alzheimer's Disease Center, as well as 57 men who did not have PPA, with an age range of 55 to 80.
They found that of those with primary progressive aphasia, 40 percent had undergone a vasectomy, compared to 16 percent of the others.
Those with PPA had developed the condition an average of four years earlier than the others.
The researchers say preliminary data also linked vasectomies to another form of dementia involving behavioural changes, where it was found that among 30 men with frontotemporal dementia, more than a third had undergone a vasectomy.
Lead study author Sandra Weintraub recognises that the research involved a small number of people but says a larger national study is planned in order to establish whether the findings hold up.
Weintraub says the findings should not stop men from getting vasectomies as the the study is a clinical observation originating from patients first noticing the onset of symptoms a few years after the vasectomy.
Primary progressive aphasia, which affects people usually after age 50, can be mistaken for Alzheimer's disease since initial symptoms are similar.
The disorder is incurable as nerve cells die in the brain region responsible for language skills.
The condition causes language capabilities to decline steadily, along with faulty recollection of names of people and things, difficulties in speech, reading and writing, and poor comprehension.
In a vasectomy the tubes through which sperm travels are cut, leaving sperm unable to reach the testes and making a man unable to impregnate a woman.
Weintraub suggests the surgery allows sperm to leak into the blood and antibodies produced by the immune system in response to the sperm, possibly trigger the damage that causes dementia.
Antisperm antibodies can also develop in women and become risk factors for PPA.