The loss or deterioration of intellectual capacity in people suffering from conditions, such as Alzheimer's disease or similar forms of irreversible dementia. Severe cognitive impairment must be measured by clinical evidence and standardized tests that reliably measure impairment in the individual's short-term or long-term memory, orientation as to people, places or time, and deductive or abstract reasoning.
A deterioration or loss in intellectual capacity that results in impairment of some or all of the following: short and long term memory; orientation to people, place, and time; deductive and abstract reasoning (including judgement); and ability to perform activities of daily living.