Description

• Mild cognitive impairment (MCI) is defined as significant cognitive impairment in the absence of dementia, as measured by standard memory tests:
  • Concern regarding change in cognition
  • Preservation of independence in functional activities of daily living (ADLs)
  • Impairment in ≥1 cognitive domains (attention, executive dysfunction, memory, learning, visuospatial, language)
  • Other terms used in the literature relating to MCI: cognitive impairment not dementia (CIND); mild cognitive disorder; some of these conditions do not progress to dementia. DSM-5 mentions “mild neurocognitive disorder” (mNCD), which may be a precursor to Alzheimer disease and has many of the same features as MCI.
• Older adults with MCI are 3 times more likely to progress to dementia in 2 to 5 years than age-matched cohorts (1)[A].

Epidemiology

Incidence

• Predominant sex: male > female
• Predominant age:
  • Higher in older persons and in those with less education
  • 12 to 15/1,000 person-years in those aged ≥65 years
  • 50 to 75/1,000 person-years in those aged ≥75 years

Prevalence

• MCI is more prevalent than dementia in the United States.
• 12–18% for those aged ≥60 years; ~25% for ages 80 to 84 years; prevalence increases with age and for those with lower educational level (2).

Etiology and Pathophysiology

• Subtypes of MCI:
  • Single-domain amnestic
  • Multiple-domain amnestic
  • Single-domain nonamnestic
  • Multiple-domain nonamnestic
• The amnestic subtypes are higher risk for progression to Alzheimer disease.
• Vascular, neurodegenerative, traumatic, metabolic, psychiatric, or a combination

Genetics
In certain subsets of MCI where the disease will progress to Alzheimer disease, one must consider apolipoprotein (APO) E4 genotype: Various pathways exist leading to amyloid accumulation and deposition thought to be associated with Alzheimer disease.

Risk Factors

• Diabetes; hypertension; hyperlipidemia; cerebrovascular disease
• Smoking
• Sleep apnea
• APO E4 genotype
• Low educational levels
• Depression
• Sedentary lifestyle

General Prevention

Optimize vascular risk factors and focus on a healthy, active lifestyle.

Commonly Associated Conditions

See “Risk Factors.”