After the birth of his first child, Dr. Peter Attia became his own first patient in a new speciality: longevity medicine.  Today, the Stanford-trained doctor is prescribing a radical change in how Americans think about their own health care. His patient-driven, prevention-focused "Medicine 3.0" concept is designed to help people thrive in the last decade of their lives, a period typically plagued by sickness and immobility. "The marginal decade's not going anywhere. We will all have a final