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What is Mild cognitive impairment and explain in detail?
Mild cognitive impairment (MCI) is a neurocognitive disorder which involves cognitive impairments beyond those expected based on an individuals age and education but which are not significant enough to interfere with instrumental activities of daily living. MCI may occur as a transitional stage between normal aging and dementia, especially Alzheimers disease. It includes both memory and non-memory impairments. The cause of the disorder remains unclear, as well as both its prevention and treatment, with some 50 percent of people diagnosed with it going on to develop Alzheimers disease within five years.  The diagnosis can also serve as an early indicator for other types of dementia, although MCI may remain stable or even remit.Mild cognitive impairment has been relisted as mild neurocognitive disorder in DSM-5, and in ICD-11, the latter effective on the 1st of January 2022.

Classification
MCI can present with a variety of symptoms, but is divided generally into two types.Amnestic MCI (aMCI) is mild cognitive impairment with memory loss as the predominant symptom; aMCI is frequently seen as a prodromal stage of Alzheimers disease. Studies suggest that these individuals tend to progress to probable Alzheimers disease at a rate of approximately 10% to 15% per year. It is possible that being diagnosed with cognitive decline may serve as an indicator of MCI.Nonamnestic MCI (naMCI) is mild cognitive impairment in which impairments in domains other than memory (for example, language, visuospatial, executive) are more prominent. It may be further divided as nonamnestic single- or multiple-domain MCI, and these individuals are believed to be more likely to convert to other dementias (for example, dementia with Lewy bodies).The International Classification of Diseases classifies MCI as a "mental and behavioural disorder."

Causes
Mild cognitive impairment (MCI) may be caused due to alteration in the brain triggered during early stages of Alzheimers disease or other forms of dementia. Exact causes of MCI are unknown. It is controversial whether MCI even should be identified as a disorder.Risk factors of both dementia and MCI are considered to be the same: these are aging, genetic (heredity) cause of Alzheimers or other dementia, and cardiovascular disease.Individuals with MCI have increased oxidative damage in their nuclear and mitochondrial brain DNA.

Diagnosis
The diagnosis of MCI requires considerable clinical judgement, and as such a comprehensive clinical assessment including clinical observation, neuroimaging, blood tests and neuropsychological testing are best in order to rule out an alternate diagnosis. 
MCI is diagnosed when there is:
Evidence of memory impairment
Preservation of general cognitive and functional abilities
Absence of diagnosed dementia

Neuropathology
Although amnestic MCI patients may not meet criteria for Alzheimers disease, patients may be in a transitional stage of evolving Alzheimers disease.Magnetic resonance imaging can observe deterioration, including progressive loss of gray matter in the brain, from mild cognitive impairment to full-blown Alzheimer disease.  A technique known as PiB PET imaging is used to show the sites and shapes of beta amyloid deposits in living subjects using a 11C tracer that binds selectively to such deposits.

Treatment
As of January 2018, there are no USFDA-approved medications for the treatment of mild cognitive impairment.  Moreover, as of January 2018, there is no high-quality evidence that supports the efficacy of any pharmaceutical drugs or dietary supplements for improving cognitive symptoms in individuals with mild cognitive impairment. A moderate amount of high-quality evidence supports the efficacy of regular physical exercise for improving cognitive symptoms in individuals with MCI. The clinical trials that established the efficacy of exercise therapy for MCI involved twice weekly exercise over a period of six months. A small amount of high-quality evidence supports the efficacy of cognitive training for improving some measures of cognitive function in individuals with mild cognitive impairment.  Due to the heterogeneity among studies which assessed the effect of cognitive training in individuals with MCI, there are no particular cognitive training interventions that have been found to provide greater symptomatic benefits for MCI relative to other forms of cognitive training.The American Academy of Neurologys (AAN) clinical practice guideline on mild cognitive impairment from January 2018 stated that clinicians should identify modifiable risk factors in individuals with MCI, assess functional impairments, provide treatment for any behavioral or neuropsychiatric symptoms, and monitor the individuals cognitive status over time. It also stated that medications which cause cognitive impairment should be discontinued or avoided if possible