Final answer:
Alzheimer's disease is the most common cause of dementia. It affects a significant portion of the elderly population, leading to cognitive impairments.
Step-by-step explanation:
Alzheimer's disease is the most common cause of dementia in the elderly. It affects roughly one in every eight people age 65 or older and is projected to affect as many as 13 million Americans by 2050. This neurodegenerative disease is characterized by the presence of abnormal clumps called amyloid plaques and tangled brain fibers called neurofibrillary tangles. These hallmarks of the disease lead to the loss of neurons and brain volume, resulting in cognitive impairments.