Predementia constructs: Mild cognitive impairment or mild neurocognitive disorder? A narrative review

Abstract

Background: Predementia is a heuristic umbrella concept to classify older adults with cognitive impairment who do not suffer dementia. Many diagnostic entities have been proposed to address this concept, but most of them have not had widespread acceptance. Aims: To review clinical definitions, epidemiologic data (prevalence, incidence) and rate of conversion to dementia of the main predementia constructs, with special interest in the two most frequently used: mild cognitive impairment (MCI) and minor neurocognitive disorder (miNCD). Methods: We have selected in three databases (MEDLINE, Web of Science and Google scholar) the references from inception to 31 December 2019 of relevant reviews, population and community-based surveys, and clinical series with >500 participants and >3 years follow-up as the best source of evidence. Main results: The history of predementia constructs shows that MCI is the most referred entity. It is widely recognized as a clinical syndrome harbinger of dementia of several etiologies, mainly MCI due to Alzheimer's disease. The operational definition of MCI has shortcomings: vagueness of its requirement of "preserved independence in functional abilities" and others. The recent miNCD construct presents analogous difficulties. Current data indicate that it is a stricter predementia condition, with lower prevalence than MCI, less sensitivity to cognitive decline and, possibly, higher conversion rate to dementia. Conclusions: MCI is a widely employed research and clinical entity. Preliminary data indicate that the clinical use of miNCD instead of MCI requires more scientific evidence. Both approaches have common limitations that need to be addressed.

Risk Prediction Performance of the Thai Cardiovascular Risk Score for Mild Cognitive Impairment in Adults with Metabolic Risk Factors in Thailand

“…MCI is the condition that lies between normal cognitive aging and dementia. It is defined as evidence of progressive cognitive decline combined with the preservation of functional independence [ 17 ]. MCI in metabolic syndrome is higher when compared to the general population [ 18 ].…”

The effects of the interplay between vitamins, antibiotics, and gut microbiota on the pathogenesis and progression of dementia: A systematic review and meta‐analysis

“…It's called the intermediate stage of dementia as symptoms worsen. The symptom drop rate ranges from 6 to 17 MMSE scores 26 . Social judgment and problem‐solving skills are frequently weakened at this stage of dementia.…”

“…Antibiotics can diminish the variety and richness of the gut microbiota, increasing pathogenic bacteria and decreasing beneficial bacteria 59 . This dysbiosis can modify microbial metabolites including short‐chain fatty acids, which impact gut‐brain communication and neuroinflammation 26 . Antibiotics can also cause allergies, inflammatory bowel disease, metabolic problems, and cognitive impairment 27…”

“…Predementia includes prodromal and preclinical phases. Sensory dysfunction in the preclinical stage causes olfactory loss and appetite loss due to chemosensory receptor cell destruction and blood‐brain barrier interference 26 . Prodromal symptoms include behavioral and cognitive deficits, memory loss, and brain word aggregation and pronunciation issues.…”

“…59 This dysbiosis can modify microbial metabolites including short-chain fatty acids, which impact gut-brain communication and neuroinflammation. 26 Antibiotics can also cause allergies, inflammatory bowel disease, metabolic problems, and cognitive impairment. 27 Antibiotics may affect dementia progression.…”