Men who have had a vasectomy appear to have a small risk of developing two types of dementia as they age, researchers say. However, the finding is from a small study, and should not discourage men from having the procedure at this time.

The first type of dementia, primary progressive aphasia (PPA), is a neurological disease that causes difficulty with language. Unlike Alzheimer's disease, PPA causes no difficulty with memory, but instead features trouble expressing oneself and understanding others. Additionally, though PPA tends to be diagnosed earlier than Alzheimer's disease, those with PPA are able to perform complex tasks for many years, whereas those with Alzheimer's tend to lose interest in their hobbies and are unable to navigate around their neighborhood.

Though PPA is a relatively rare form of dementia, it seems that having a vasectomy increases one's risk for this disease. In a recent study, researchers from Northwestern University's Feinberg School of Medicine surveyed 47 men who had been diagnosed with PPA and 57 mentally healthy men.

Among those surveyed with PPA, 40 percent had undergone a vasectomy, surgery to permanently block the ejaculation of sperm. In comparison, only 16 percent of the healthy men with no mental illness had undergone this procedure. Additionally, those men who had a vasectomy developed PPA at a younger age, as compared to the men with PPA who did not have the surgery. There was no link found between having a vasectomy and Alzheimer's disease.

"That's a huge difference," said Dr. Sandra Weintraub, lead author of the study, published in Cognitive and Behavioral Neurology. "It doesn't mean having a vasectomy will give you this disease, but it may be a risk factor to increase your chance of getting it."

The study revealed another possible link between vasectomy and a second form of dementia called frontotemporal dementia (FTD). Among 30 men who had undergone a vasectomy, 37 percent had this form of dementia, which causes changes in one's personality, lack of judgment and bizarre behavior.

It is not clear why this link exists, but Weintraub suggests that having a vasectomy raises the risk of semen mixing into the bloodstream. This may trigger an immune response, causing the body to produce warrior cells called antibodies to defend the body against the "foreign" sperm. If these antibodies crossed into the brain, said Weintraub, they could cause damage that would result in both forms of dementia.

More work needs to be done to more conclusively link vasectomies to an increased risk of dementia, as well as to find out the reasons behind a link.

"I don't want to scare anyone away from getting a vasectomy," said Weintraub. "It's obviously a major birth control alternative [and] we need to do more research."