This is a very interesting discussion and observation. Perhaps it might fit better in the ENT group. The link provided by chasmayhear explains a highly scientific piece of unfunded research.

There is interesting information about the Valsalva Maneuver on Google. I did not know what this breathing procedure was called, but realize I have used it often when flying to get my ears to 'pop'.

I wonder if the Hearing Health Foundation, an organization focused on bringing many research bodies together to study hearing loss issues, would have information on research being done on this. http://www.hhf.org NOTE: HHF publishes a quarterly magazine that includes research studies, and personal experiences from people with a variety of hearing loss experiences. You can receive the publication free by signing up on the website.

Carotid Stenosis could be a causative factor in hearing loss for some people, but is likely rather rare. NOTE: It is important for people to understand that this maneuver also has risks related to some extenuating health issues.

Here is a bit of information I found online.

"The Valsalva maneuver is a particular way of breathing that increases pressure in the chest. It causes various effects in the body, including changes in the heart rate and blood pressure.

People may perform the maneuver regularly without knowing it. For example, they may use it when they push to initiate a bowel movement.

However, this technique can also be beneficial when people use it intentionally as it can regulate heart rhythms and help the ears to pop".