The most common cause of dementia in elderly individuals is Alzheimer's disease, accounting for approximately 60-80% of all dementia cases. It is characterized by progressive memory loss and cognitive decline due to the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain. Unlike other types, Alzheimer's disease primarily affects the hippocampus and cerebral cortex, leading to deficits in memory, language, and executive function. Early recognition and diagnosis are crucial for management and care planning.

Reference: Harrison's Principles of Internal Medicine, Kasper et al., 20th Edition.