MARC AGRONIN: The news, it seems, is not good. Health-care costs will be overwhelmed, we are told, by the “silver tsunami” that is on the way. Even a gentler description of the coming “age wave” as opposed to a destructive flood still seems to portend trouble. World War G-for-geriatric is at hand and, lacking any true fountain of youth, we are all counseled by the media to train our brains to be like younger folk–supposedly stronger, smarter and less of a burden to the system.