Which of the following is NOT a characteristic of delirium?

Delirium is characterized primarily by an acute onset of confusion, disorganized thoughts, fluctuations in consciousness, and disturbances in attention. It typically manifests rapidly and can vary in severity throughout the day.

Severe memory loss, disorganized thoughts, and changes in personality can be symptoms associated with delirium. However, long-term cognitive decline is not characteristic of delirium; rather, it is more closely associated with chronic conditions, such as dementia. Delirium is usually transient; once the underlying cause (such as infection, metabolic disturbance, or medication side effects) is identified and treated, the patient's cognitive function can often return to baseline. In contrast, long-term cognitive decline indicates a progressive deterioration of cognitive abilities over time, which is not a feature of delirium itself. Thus, identifying that long-term cognitive decline does not fall under the acute and reversible nature of delirium helps clarify the correct choice.