In Japan, the ratio of people 65 years old and over against total population is about 22 % and we face a critical problem of aging population. Accumulating evidence in the world suggests that Sirt1, an NAD(+)-dependent protein deacetylase, plays an important role in modulation of aging. We discuss a potential therapeutic target, Sirt1 and challenge for prevention of age-related diseases (Alzheimer's dementia, osteoporosis, sarcopenia, arteriosclerosis and cancer).