Mild Cognitive Impairment

BASICS

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 age ≥65 years
    • 50 to 75/1,000 person-years in those age ≥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
    • Nonamnestic single domain
    • Nonamnestic multiple domain
  • 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.”

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