Sleeping more than nine hours a night and not finishing high school are two major signs to look for when it comes to determining dementia risk in senior citizens, according to a new study. Researchers analyzed data from the country’s longest-running study looking at diseases, the Framingham Heart Study, to determine dementia risk factors. More than 2,400 subjects, at least 65 years old, responded to questions about sleep habits; 234 were diagnosed with dementia within 10 years of their original responses.