Delirium and dementia are the most common causes of cognitive impairment. Delirium is acute confusion that mostly affects attention and is usually reversible. It is most common in hospitalized patients, especially when they are elderly. Dementia mostly affects memory and is the most common cause of cognitive impairment, usually due to anatomic changes in the brain. Alzheimer’s disease (AD) is the most common cause of dementia and involves progressive atrophy and death of brain cells. More than 44 million people, globally, live with AD or a related form of dementia. Vascular dementia is usually due to diffuse or focal cerebral infarction from cerebrovascular disease. Parkinson’s disease dementia involves Lewy bodies in the cortex and substantia nigra and develops late in the disease course. Lewy body dementia is chronic cognitive deterioration and is the third most common type of dementia. Frontotemporal dementia basically affects the frontal and temporal lobes, affecting language, personality, and behavior. Chronic traumatic encephalopathy sometimes occurs after repetitive head trauma (such as from playing sports) or blast injuries. Both delirium and dementia lead to increased mortality in older individuals. For dementia patients, a family member, guardian, or attorney usually must be appointed to oversee their affairs once they become cognitively incapacitated.
Clinical Neuroepidemiology of Acute and Chronic Disorders, First Edition, 2023, pp 199-211,