Problems with memory are a very common complaint in the elderly and are not synonymous with dementia. Some degree of cognitive decline, manifested as greater difficulty in learning and retrieving new information for instance, develops with normal aging. Thus many older patients do not perform at the same level they did when they were younger but they do perform well when compared to their peers. For many, cognitive change ends at this stage and they proceed to lead normal, healthy, dementia-free lives.
The cohort that has cognitive changes beyond what is expected in normal aging but does not yet meet criteria for dementia concerns clinicians greatly as many of these patients eventually become demented. These patients usually go through a latent stage in which neurodegenerative pathology silently spreads in the brain. Once there is enough pathological burden, cognitive decline beyond what is expected for normal aging can be detected by formal neuropsychological testing. Frequently such patients go through a state called mild cognitive impairment (MCI). In this state patients are still functionally intact and live independently, but show cognitive impairment relative to the age- and education-adjusted norms.
The MCI state in itself is a prominent risk factor for developing dementia. Most patients with amnestic MCI develop Alzheimer’s disease (AD) dementia over time. At six years, as many as 80% progress to AD. Thus, MCI is a very important topic of research and an increasingly important topic of clinical care.