The average length of human life is currently 75 to 78 years and may increase to 85 years during the coming two decades, but it is not clear whether these additional years will be satisfying to live. Most data indicate modest gain in the number of healthy years lived but a far greater increase in years of compromised physicaL mental and social function. The number of days of restricted activity and the number of admissions to hospitals and nursing homes sharply increases after age 70. One U.S. health interview survey indicates that. at present, more than 25 million aging people suffer from physical impairment. whereas the number of people requiring assistance in activities of daily living increases from 14% at age 65 to 75 to 45% in those over 85 years old.