Dementia is a serious brain disorder that interferes with a person's ability to carry out everyday tasks. Because dementia is usually progressive, early signs may be vague and subtle.
The key feature of dementia is a decline in cognitive functions. These are mental processes such as thinking, reasoning, learning, problem solving, memory, language, and speech.
Other features that occur frequently in dementia include changes in personality and behavior.
Generally, these symptoms are not considered dementia unless they have continued continuously for at least six months.
Dementia has many different causes. Some may be reversible, such as certain infections, drug interactions, and liver diseases. Of the irreversible causes, the most common in older adults is Alzheimer's disease.
Although dementia is frequently linked to old age ("getting senile"), it is not a normal part of aging. Even children with certain degenerative brain disorders can develop dementia.
Causes of Memory Loss and Early Dementia
Many older people fear that they have Alzheimer's disease because they can't find their eyeglasses or remember someone's name. These very common problems are most often due to slowing of mental processes with age. While it is a nuisance, it does not significantly impair a person's ability to learn new information, solve problems, or carry out everyday activities, as Alzheimer's disease does.
Memory loss follows a specific pattern in Alzheimer's disease. The losses are mainly in short-term memory. This means that the person has problems remembering recent events, such as what he or she did last week or instructions the doctor gave this morning for taking a new medicine. The inability to recall recent events contrasts sharply with the person's ability to remember minor details and events from years earlier.
The memory loss characteristic of Alzheimer's disease is followed by many other cognitive and behavioral symptoms. Eventually, over many years, the person loses many mental and physical abilities and requires round-the-clock care.
Mild cognitive impairment (MCI) is the term used by medical professionals when memory loss is greater than what "normally" occurs with aging, but a person is still able to perform normal daily activities. MCI is generally considered to be an early form of Alzheimer's disease.
MCI is a transitional zone between age-related memory loss and early Alzheimer's disease. A person is often said to have MCI when he or she has Alzheimer's-like memory loss while overall thinking and reasoning skills are maintained.
Memory loss in MCI is more severe than purely age-related memory loss.
There are other types of MCI, but the type involving short-term memory loss is the most common. Medical professionals call this type "amnestic" MCI. Amnestic has the same root as the word amnesia, meaning memory loss.
From studies in the brains of people with Alzheimer's disease or amnestic MCI, we know that the changes are similar. Therefore, amnestic develops full dementia. However, people with MCI are more likely than other elderly people to develop Alzheimer's disease.
It's unclear how many people have MCI, nor which factors contribute to the progression from MCI to Alzheimer's disease.
A large, three-year study reported last year demonstrated that treatment with the medication Aricept could slightly delay, but not prevent, the transition from MCI to Alzheimer's.