Objective: To estimate the prevalence and examine the course of mild cognitive impairment (MCI), amnestic type, using current criteria, within a representative community sample. Methods: Retroactive application of MCI criteria to data collected during a prospective epidemiologic study was performed. The subjects were drawn from voter registration lists, composing a cohort of 1,248 individuals with mean age of 74.6 (5.3) years, who were nondemented at entry and who were assessed biennially over 10 years of follow-up. The Petersen amnestic MCI criteria were operationalized as 1) impaired memory: Word List Delayed Recall score of <1 SD below mean; 2) normal mental status: Mini-Mental State Examination score of 25+; 3) normal daily functioning: no instrumental impairments; 4) memory complaint: subjective response to standardized question; 5) not demented: Clinical Dementia Rating Scale score of <1. Results: At the five assessments, amnestic MCI criteria were met by 2.9 to 4.0% of the cohort. Of 40 persons with MCI at the first assessment, 11 (27%) developed dementia over the next 10 years. Over each 2-year interval, MCI persons showed increased risk of dementing (odds ratio = 3.9, 95% CI = 2.1 to 7.2); 11.1 to 16.7% progressed to Alzheimer disease and 0 to 5.0% progressed to other dementias. Over the same intervals, 11.1 to 21.2% of those with MCI remained MCI; of 33.3 to 55.6% who no longer had MCI, half had reverted to normal. Conclusions: In this community-based sample, 3 to 4% of nondemented persons met MCI operational criteria; despite increased risk of progressing to dementia, a substantial proportion also remained stable or reverted to normal during follow-up. Amnestic MCI as currently defined is a high-risk but unstable and heterogeneous group.

Research from JAMA Psychiatry — Depressive Symptoms and Cognitive Decline in Late Life — A Prospective Epidemiological Study

Mild cognitive impairment (MCI), the cognitive state intermediate between normal cognition and dementia, is interesting because of the potential for MCI to eventually develop into full-blown dementia. The original Mayo Clinic criteria for amnestic MCI¹ focused on deficits in and complaints about memory. The revised International Working Group (IWG) on Mild Cognitive Impairment criteria² expanded the concept to include objective and subjective impairments in any of several cognitive domains. The Clinical Dementia Rating (CDR)³ approach focuses on decline in cognitively driven everyday function rather than on objective cognitive deficits. Other approaches have used purely neuropsychological definitions of MCI based on objective deficits relative to norms.^4-7 Regardless of the definition used, individuals with MCI progress to dementia in higher proportions than do cognitively normal people; however, the actual proportions vary across definitions^4,5,8-10 and across operational versions of the same definitions.^11-13 Rates of progression from MCI to dementia are consistently lower in community settings than in specialty clinical and research programs where individuals with MCI seek services^11,12 despite using the same criteria.¹⁴ All population-based studies^4,8,10-12 find substantial proportions of individuals with variously defined MCI remaining stable or even reverting to normal during follow-up.

Research from JAMA Neurology — Alzheimer Disease and Mortality — A 15-Year Epidemiological Study