The National Institute of Justice has launched a page on the website entitled, “Factors that Affect Officers’ Use of Body Armor.” It is meant to aggregate any studies that they have conducted relative to the use of body armor by law enforcement officers.
Currently, there are two topics with supporting documentation: Agency Policies Promote Use of Body Armor and Comfort of Body Armor. One interesting role NIJ has taken in the improvement of body armor comfort is in the realm of fit. They have worked with the American Society of Testing and Materials to develop standards for fitting armor so that industry and consumers alike will work from a common point of view for sizing.
This is a great resource.