Alzheimer Disease l: Introduction

Alzheimer disease is a chronic, progressive, and irreversible neurodegenerative disorder and the most common cause of dementia in older adults. It leads to gradual neuronal loss, causing cognitive decline, behavioral changes, and loss of functional independence.

Risk Factors and Etiology

The disease is multifactorial. Age is the strongest risk factor, with prevalence doubling every 5 years after age 65. Genetic factors include mutations in genes such as APP, PSEN1, and PSEN2, which are associated with early-onset, while mutations in the APOE ε4 allele increase risk of late-onset disease. Individuals with Down syndrome develop early Alzheimer-related changes due to an extra APP gene copy. Females are at higher risk, partly because of their longer lifespan.

Modifiable factors include hypertension, stroke, and obesity, which impair cerebral blood flow. Type 2 diabetes promotes inflammation, vascular damage, and accelerates neurodegeneration. Head trauma increases abnormal protein accumulation in the brain. While smoking adds to the oxidative stress, elevated homocysteine levels due to depression are linked to cognitive decline. Family history also raises risk due to shared genetic and environmental factors.

Clinical Manifestations

Early symptoms include difficulty learning new information and short-term memory loss. Progression leads to impaired memory formation, repeated forgetting, and inability to retain new information. Language deficits (aphasia), difficulty with calculations (acalculia), and naming objects (anomia) develop. Patients struggle with daily tasks, judgment, and orientation. Advanced stages include failure to recognize familiar people, psychiatric symptoms (paranoia, hallucinations), and motor changes such as slowed movement and gait disturbances.