Alzheimer’s disease is associated with -a) Deleriumb) Delusionc) Dementiad) Depression

**Core Concept**
Alzheimer's disease is a neurodegenerative disorder characterized by progressive cognitive decline, memory loss, and neuronal degeneration. The condition is primarily associated with the accumulation of amyloid beta plaques and tau protein tangles in the brain, leading to neuronal dysfunction and death.

**Why the Correct Answer is Right**
The correct answer is **C) Dementia**. Dementia is a chronic or persistent disorder of the mental processes caused by brain disease or injury and marked by memory disorders, personality changes, and impaired reasoning. Alzheimer's disease is the most common cause of dementia, accounting for 60-80% of cases. The disease leads to a gradual decline in cognitive function, including memory loss, language difficulties, and problems with thinking and judgment.

**Why Each Wrong Option is Incorrect**
**Option A:** Delirium is a sudden and temporary change in mental status, often caused by medical conditions, medications, or environmental factors. While delirium can coexist with dementia, it is not a characteristic feature of Alzheimer's disease.
**Option B:** Delusion is a firm belief in something that is not true, often seen in psychiatric conditions such as schizophrenia. Delusions are not a primary feature of Alzheimer's disease, although some patients may experience psychotic symptoms as the disease progresses.
**Option D:** Depression is a common comorbidity in Alzheimer's disease, but it is not a defining characteristic of the condition. Depressive symptoms can occur in response to the diagnosis, disease progression, or treatment.

**Clinical Pearl / High-Yield Fact**
Alzheimer's disease is a heterogeneous condition, and its clinical presentation can vary widely between individuals. However, the presence of dementia is a hallmark feature of the disease, and its diagnosis is typically made based on a combination of clinical evaluation, laboratory tests, and imaging studies.

**Correct Answer:** C. Dementia