What is the prognosis of mild cognitive impairment (MCI)?

Updated: Apr 22, 2019
  • Author: Sonal Mehta, MD; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Answer

Many patients with mild cognitive impairment (MCI) eventually experience progressive deterioration in their abilities to perform activities of daily living, cognition, and behavior.

Subtypes of MCI progress to Alzheimer disease (AD) at different rates. A study by Rountree et al showed that the conversion rate to AD was 56% for amnestic MCI, 50% for amnestic-subthreshold MCI, and 52% for nonamnestic MCI. [40] For all MCI subtypes, the 4-year conversion rate to dementia was 56% (14% annually), and that to Alzheimer disease was 46% (11% annually).In comparison, healthy elderly individuals develop AD at a rate of 1-2% per year.

Boyle et al reported that patients with MCI are almost 7 times more likely to develop AD than are older individuals without cognitive impairment. [41] Of patients with MCI, 80% are said to progress to dementia after approximately 6 years. This is a significant finding, given that AD is often cited as the fourth leading cause of death in the United States.

At least one well-designed study has shown MCI, as identified by the Short Portable Mental Status Questionnaire, to be an independent predictor of mortality. [42] Wilson et al reported that in both African American and white patients, the risk of death was increased by about 50% among individuals with MCI and was nearly 3 times higher among those with AD. [43]

Ultimately, long-term follow-up and eventual autopsy are necessary to distinguish between patients experiencing MCI due to preclinical AD and patients experiencing MCI due to less frequently occurring conditions. However, there are some factors that can be helpful in predicting the likelihood of progression.

The severity of memory impairment is predictive of progression to AD: patients with more severe memory impairment are more likely to progress. There are certain neuroradiologic features that predict progression of MCI. These include MRI findings of atrophy and volume loss in the medial temporal lobe as well as a hypometabolic pattern on FDG-PET scan. [44, 45, 3] In addition, APOE4 genotype carriers are at higher risk of progression, but APoE4 testing is not recommended for routine use. [46] A new modality that might prove useful in predicting and monitoring progression of MCI is a new PET tracer focusing on the role of tau. Early data suggests that spread of tau laterally, outside the medial temporal lobe, may predict a poor prognosis and a more rapid progression. [47]


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