More than a third of adults will have been diagnosed with dementia, the progressive loss of cognitive function, by the time they reach the age of 90. Though the disorder is widespread, it is not an inevitable part of aging. This special edition of Health decodes the subsets of dementia and details the steps you can take throughout your life to keep it at bay and promote healthy aging. Topics include questions to ask your doctor after diagnosis, an overview of Alzheimer's disease, how to prevent falls at home, and tips for loved ones to cope.