We are growing older. In ancient Greece, the expected life span was 20 years. In Medieval Europe, it went up to 30 years. In 1900, people reasonably could expect to live to the ripe old age of 47 years, and 39% of those born at that time survived to age 65 years in the United States. Currently, the average life span in the United States is 78 years, and 86% of those born will survive to age 65 years. The very old—people older than 85 years—are the fastest-growing population group in the country, and there are 120,000 Americans over the age of 100 years. And the trend continues.