Bartender Matt Carucci says he rarely feels safe biking in the city but often rides without a helmet anyway. "There are a lot of other ways to hurt yourself," he says. John Rose/NPR hide caption

itoggle caption John Rose/NPR

The most common cause of brain injury in premature infants is a lack of oxygen in the days and weeks after birth, researchers say. Ibrahim Usta/AP hide caption

itoggle caption Ibrahim Usta/AP