The absolute numbers of older Americans with dementia are sure to grow as the population ages in the coming decades, but new data suggest that the overall proportion with the condition is mysteriously declining. That positive news emerged yesterday in a study in JAMA Internal Medicine showing that in percentage terms, the number of demented people 65 and older fell by 25% between 2000 and 2012. As this article in STAT points out, the decline, from 11.6% of over-64-year-olds in 2000 to 8.8% in 2012, translated to more than 1 million fewer elderly people with dementia in 2012 than would have resulted had the 2000 prevalence remained unchanged. The decrease may be tied to better education; the 2012 cohort had about a year more formal education than the 2000 group. But that doesn’t completely explain the fall off, the authors say. Figuring out what else contributed could be a big help in battling dementia in a graying United States.