Final answer:
Alzheimer's disease is the most common cause of dementia, marked by the presence of amyloid plaques and neurofibrillary tangles in the brain and resulting in cognitive decline.
Step-by-step explanation:
The leading cause of dementia is Alzheimer's disease. Alzheimer's disease is a neurodegenerative condition characterized by the loss of neurons, particularly in the hippocampus, and the presence of amyloid plaques and neurofibrillary tangles. These pathologies cause a significant decline in cognitive abilities, resulting in dementia. It is the most common type of dementia found in the elderly, and the prevalence is increasing due to the aging population. Solomon Carter Fuller was one of the early researchers studying this disease. In 2012, an estimated 5.4 million Americans were affected by Alzheimer's, with substantial costs for their care.