I'm making a real-time 2D MMORPG in Java. Currently data all surrounding NPCs' and players' data is sent so frequently that the client crashes—it can't handle the data quickly enough. I'm sending data so frequently to make sure the game state stays up to date.

Is there an alternative? Should I make it send information only when needed, like when health is lost or something moves, instead of updating the whole object every time? How do I do this?