They 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. Their ages ranged from 55 to 80.
Of those with primary progressive aphasia, 40 percent had undergone a vasectomy, compared to 16 percent of the others. Those with PPA also suffered the ailment an average of four years earlier than the others.
Preliminary data also linked vasectomies to another form of dementia involving behavioral changes. Among 30 men with frontotemporal dementia, more than a third had undergone a vasectomy, the researchers said
(...)The study did not look at the mechanism behind any link between PPA and vasectomies, but Weintraub said it may be because the surgery allows sperm to leak into the blood. Antibodies produced by the immune system in response to the sperm might trigger damage that causes dementia, she said.
source.
There's a joke in there, somewhere.
