The following is an analysis of the publication:

“Vasectomy in Men with Primary Progressive Aphasia”

Reference: Cogn Behav Neurol. 2006 Dec;19(4):190-3.

This study originated from one patient’s belief that the dementia he was suffering from appeared after his vasectomy. This was not a common dementia; it was a relatively new kind of dementia called Primary Progressive Aphasia (PPA). PPA was first described in 1982 by Marsell Mesullam. Its onset is characterized by language impairment (aphasia) rather than the forgetfulness found in Alzheimer’ s disease (AD).

Another reason for the study was the interesting fact that the testis and the brain have similar molecular substances. One of the substances they have in common is a protein called tau. Tau stabilizes the structure of the sperm, and it also stabilizes the structure of the supportive neuronal cells in the brain. Mutations of tau are known to cause frontotemporal dementia (FTD). The authors of this study did not specifically study FTD, but they noted that, in their registry of patients with FTD, 37% had vasectomies.

The authors found that 40% of the men in their study who suffered from PPA had vasectomies. The study had a control group of males who did not have PPA, and 16% of that group had vasectomies.

The conclusion of the article is that vasectomy may constitute a risk for PPA in men.

The explanation of how could this happen is an intellectual exercise. Let’s exercise.

Consider that a typical man produces millions of sperm daily. The area of the body in which sperm are produced is surrounded by a very delicate barrier called the blood testis barrier. Inside the barrier are all the manufacturing components for the sperm. After vasectomy this barrier is disrupted and all these manufacturing components of the sperm are set free in the blood stream. The response of the immune system after a vasectomy is impressive. These manufacturing components now become substances that are attacked by the immune system by way of anti-substances (antibodies). Antibodies to sperm and sperm components are found in 60% to 70% of men after vasectomy and these antibodies may persist for years. The immune system after a vasectomy has the potential to attack important components of the brain tissue because of their molecular similarity with sperm components. The length of time that the body continues its immune response to sperm components seems to be important for development of PPA. The study revealed that PPA subjects had the vasectomy procedure at a younger age— 36 years old on average. In contrast the control group had their vasectomies performed at an average age of 43.56 years. It appears that longer exposure to this sort of immune attack increases the probability of developing PPA.

Based on what we know of immune reactions to sperm and of similarity of brain and sperm proteins, it is reasonable to say that vasectomy may have a role in the development of PPA.