Quality of life—we all want it. And it’s affected as we age. With medical advances and improvements in the environment, average lifespan is now about 70 years. But as we live longer, it’s become clear that quality of life trumps quantity, or length, of life. Age brings physical changes. As your physical health declines, your muscles get weaker, your memory fades, your vision and hearing dwindle . . . What causes this? And can you change it?