Chapter 243: Dementia

PATIENT STORY

A 70-year-old woman is brought to the physician by her daughter, who is concerned that she is becoming forgetful. She has hypertension but is otherwise healthy and lives independently. A neurologic examination is normal, with the exception of mild cognitive decline on an objective assessment. You recommend testing to evaluate for reversible causes of cognitive decline, including an MRI.

INTRODUCTION

Dementia is present in approximately 6% of adults over the age of 60 and increases with age. Dementia is now called minor or major neurocognitive disorder based on severity and can be due to many different disease processes. Alzheimer disease, vascular dementia, frontotemporal dementia, and dementia with Lewy bodies are the most common types of dementia. Dementia is a clinical diagnosis, although biomarkers can now assist with differentiating types of dementia. Treatments may slow decline, but the course is progressive.

EPIDEMIOLOGY

• In most areas of the world, 5% to 7% of adults over 60 years of age have dementia. The prevalence is slightly higher in Latin America (8.5%) and lower in sub-Saharan Africa (2%–4%).¹

• In 2010, approximately 36 million people were living with dementia, a number that is expected to double every 20 years.¹

• The pooled prevalence of dementia increases with age. Almost 45% of adults age 95 or older have dementia.²

• In 2010, Alzheimer disease (AD) was the 6th leading cause of death in the United States and the leading cause of death in people over the age of 65.³

• In the United States, health care for people age 65 and older with dementia costs an estimated $214 billion each year; unpaid caregivers provide a contribution estimated to be an additional $220 billion.³

ETIOLOGY AND PATHOPHYSIOLOGY

Dementia can be due to a number of different disease processes.

• AD, 50% to 70% of dementia cases—Progressive loss of neurons, buildup of amyloid plaques and neurofibrillary tangles, and decline in presynaptic cholinergic function.

• Vascular dementia, 20% of dementia cases—Cerebrovascular disease in large or small vessels.

• Frontotemporal dementia (FTD), 5% of dementia cases—Atrophy of frontal and temporal lobes, tau or protein TDP-43 accumulation; Pick disease is a subtype with intracellular tau (Pick bodies).

• DLB, 5% of dementia cases—Progressive loss of neurons due to alpha-synuclein misfolding and aggregation within Lewy bodies.

• Less common causes of dementia are Parkinson disease (although dementia is common in patients with Parkinson disease), Huntington disease, prion disease, HIV/AIDS, or multiple sclerosis.

DIAGNOSIS

Criteria for major neurocognitive disorder (dementia) from the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5):

• Significant cognitive decline (observed by a clinician or reliable informant or documented on an objective cognitive assessment).

• Substantial loss of independence in everyday activities.

• Not present only during delirium or better explained by another diagnosis.