Early Detection of Cognitive Impairment: Do Screening Tests Help?

摘要

Dementia is defined as an acquired loss of memory that is substantial enough to interfere with everyday functioning. Although many types of dementia exist, most patients with dementia have Alzheimer's disease (AD), vascular dementia, or Lewy body dementia. Age is the greatest risk factor for developing dementia; its incidence and prevalence increase dramatically in persons older than 65 years. Specifically, AD affects approximately 25% to 30% of individuals older than 65 years and doubles in incidence for every 5 years thereafter. As a result, the prevalence of AD approaches 50% among persons older than 85 years. Genetic risk factors have also been related to AD. The most prevalent is the apo-lipoprotein E (APOE) e4 allele. Caselli et al explored the age-related trajectories of memory loss in APOE carriers and noncarriers and found that homozygous carriers have earlier onset of memory impairment than noncarriers in the absence of mild cognitive impairment (MCI) or AD. Patients with AD have an average life expectancy of 8 to 10 years after symptom onset and as the disease progresses a loss in activities of daily living ensues. This entails caregiver burden and with time it becomes so overwhelming that it is a major contributing factor to the decision to institutionalize a patient with dementia. One approach to this highly prevalent disease is its early detection for early treatment and prevention. For this reason recent research has focused on detection of early dementia and the transitional stage of cognitive impairment between normal aging and early dementia, so-called mild cognitive impairment. Figure 1 gives a simple approach to the diagnosis of dementia and MCI. This article intends to point out the ability of current screening tools to detect MCI and dementia, and to summarize 3 aspects of these conditions: prognosis, diagnosis, and treatment, in the community as well as nursing home settings.