A new study shows that one of every 10 adults over the age of 65 in this country has dementia. Over one in every five has some cognitive challenges. In the study, published in the journal JAMA Neurology, researchers analyzed the cognitive test results of 3,500 participants 65 and older. Those tests measured aspects such as attention, memory, and comprehension. The rates of dementia proved to be roughly the same for men and women, but dementia clearly increased as participants got older, with 35 percent of those in their nineties having dementia. In terms of race and education, the rates of dementia were higher for Blacks as well as those with no high school diploma.