Reducing your risk of Alzheimer’s: what one Greek island shows us

There’s a 50-50 chance a person in America will be diagnosed with Alzheimer’s disease after age 85 – but on a Greek island, the disease is almost non-existent. Is that because of their genes, or the food they eat, or the air they breathe? NBC special anchor Maria Shriver goes to an unlikely place, Cleveland, to find some answers.