People everywhere are living longer than ever. The average global life expectancy has more than doubled since 1900 and now exceeds 70 years. Vaccines and antibiotics have reined in scourges like polio, tuberculosis and pneumonia, which can strike young and old people alike. This helps explain why diseases that have long been more common in the elderly, such as cancer and cardiovascular ailments, are today leading causes of mortality, making up more than 35 percent of all deaths. In the United states, roughly half of all adults suffer from at least one sort of ongoing, incurable illness, including cancer, multiple sclerosis, rheumatoid arthritis and diabetes.
