In this study of a cohort of adults with genetic mutations that cause autosomal dominant Alzheimer's disease, researchers identified abnormalities in cerebrospinal fluid biomarkers and neuroimaging tests that develop decades before the onset of dementia. Alzheimer's disease is the most common cause of dementia and is currently estimated to affect more than 5 million people in the United States, with an expected increase to 13 million by the year 2050. The typical clinical presentation is progressive loss of memory and cognitive function, ultimately leading to a loss of independence and causing a heavy personal toll on the patient and the family. The costs of care of patients with Alzheimer's disease in 2010 were estimated at more than $172 billion in the United States, an annual cost that is predicted to increase to a trillion dollars . . .