Cognitive impairment and dementia are two terms used to refer to problems associated with a decline in the normal use of the mental faculties. The connection between cognitive impairment and dementia stems from the fact that cognitive impairment is usually a precursor to dementia. In other words, cognitive impairment is less serious than dementia.
When talking about the relationship between cognitive impairment and dementia, it is usually in terms of the fact that cognitive abilities are often gradually lost in the process of developing full-blown dementia. Cognitive abilities refer to the ability to use the mental resources to function fully and capably in all areas of daily life, including the use of the memory. As part of the process of losing the cognitive ability, one of the first components to go is the memory, which experiences a decline in its function while the individual with the condition is still able to live his or her life except for the ability to recall events in their entirety. This is different from dementia, a condition that is far more incapacitating due to the fact that it seriously affects the ability of an individual to function in the usual capacity he or she enjoyed prior to the onset of dementia.
The link between cognitive impairment and dementia can be seen in the way some people who have cognitive impairment behave in relation to the way the people who have dementia behave. Some outward manifestation of cognitive impairment consists of losing train of thought, forgetting where items have been placed, and forgetting little details like the reason for deciding to do something, such as walking outside the door. While such impairments are in the nature of nuisances, they do not seriously hamper the ability of the individual to continue with other activities. On the other hand, dementia most commonly affects the individuals in a more profound manner, often manifesting in a total overhaul of his or her usual behavior.
In this connection between cognitive impairment and dementia, the individual who has developed dementia might start behaving in a manner that is different to what was the case previously, before the onset of the condition. For example, the person's personality might change entirely due to the effect of the condition. Someone who was previously considered levelheaded and sweet might become overly aggressive, exhibiting frequent outbursts of aggression as the condition progresses.