WASHINGTON — The United States suffers far more violent deaths than any other wealthy nation, due in part to the widespread possession of firearms and the practice of storing them at home in a place that is often unlocked, according to a report released Wednesday by two of the nation’s leading health research institutions.

Gun violence is just one of many factors contributing to lower US life expectancy, but the report took on urgency because it comes less than a month after the shooting deaths of 26 people at an elementary school in Newtown, Conn.