The longest study of Alzheimer's disease and dementia in the U.S. found that the rates of these disorders are dropping. A person over 60 in the U.S. is 44 percent less likely to develop dementia today than his counterpart 30 years ago. Other wealthy countries, including Sweden, England, Germany, and the Netherlands, are also experiencing declines. "The results bring some hope that perhaps dementia cases might be preventable, or at least delayed," said Claudia Satizabal of Boston University, the leader of the longitudinal study on U.S. cases. However, rates appear to be rising in East Asian and Sub-Saharan Africa, suggesting knowledge of risk factors and better health care may contribute to combatting these memory disorders.