Memory and aging

Age-related memory loss, sometimes described as "normal aging" is qualitatively different from memory loss associated with dementias such as Alzheimer's disease, and is believed to have a different brain mechanism.

Mild cognitive impairment (MCI) is a condition in which people face memory problems more often than that of the average person their age. These symptoms, however, do not prevent them from carrying out normal activities and are not as severe as the symptoms for Alzheimer's disease. Symptoms often include misplacing items, forgetting events or appointments, and having trouble finding words.

According to recent research, MCI is seen as the transitional state between cognitive changes of normal aging and Alzheimer's disease. Several studies have indicated that individuals with MCI are at an increased risk for developing AD, ranging from 1% to 25% per year; in one study 24% of MCI patients progressed to AD in 2 years and 20% more over 3 years, whereas another study indicated that the progression of MCI subjects was 55% in 4.5 years. Some patients with MCI, however, never progress to AD.

Studies have also indicated patterns that are found in both MCI and AD. Much like patients with Alzheimer's disease, those suffering from mild cognitive impairment have difficulty accurately defining words and using them appropriately in sentences when asked. While MCI patients had a lower performance in this task than the control group, AD patients performed worse overall. The abilities of MCI patients stood out, however, due to the ability to provide examples to make up for their difficulties. AD patients failed to use any compensatory strategies and therefore exhibited the difference in use of episodic memory and executive functioning.

Normal aging is associated with a decline in various memory abilities in many cognitive tasks; the phenomenon is known as age-related memory impairment (AMI) or age-associated memory impairment (AAMI). The ability to encode new memories of events or facts and working memory shows decline in both cross-sectional and longitudinal studies. Studies comparing the effects of aging on episodic memory, semantic memory, short-term memory and priming find that episodic memory is especially impaired in normal aging; some types of short-term memory are also impaired. The deficits may be related to impairments seen in the ability to refresh recently processed information.

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