What sort of disease is cognitive impairment?

Typically neurodegen: (amnestic) mild cognitive impairment (mcia) is a clinical term used to describe a phase of life that falls between pre symptomatic (have illness but no symptoms at all) and mild dementia due to alzheimer's disease. The person is forgetful and their memory recall tests between normal and frankly abnormal and they remain independent in their activities of daily living. It can progress o 1-9 years.

Not a disease: This is a variation in pattern of function not a disease. Although it is seldom recognized until the person shows signs (later childhood or adulthood), they are either born with it or they acquire it through injury or illness.