Prevalence and natural course of aging-associated cognitive decline in a population-based sample of young-old subjects

Objective: "Mild cognitive impairment" refers to cognitive deficits in older age that exceed age-related cognitive decline but do not fulfill criteria for dementia. Affected subjects are assumed to be at higher risk for the development of dementia, such as Alzheimer's disease. However, little is known about the group of young-old subjects with respect to the prevalence and natural course of cognitive decline. Method: Within the population-based Interdisciplinary Longitudinal Study on Adult Development and Aging, neuropsychological functioning was assessed in 500 community-dwelling young-old subjects of two German urban regions who were born during 1930-1932. The participants were carefully screened for physical and mental health and reexamined 4 years later. The concept of "aging- associated cognitive decline" was applied. Results: At baseline, 13.4% of the subjects fulfilled criteria for aging-associated cognitive decline. Four years later, the prevalence rates for rose to 23.6%; 52.3% of the subjects initially classified as having aging-associated cognitive decline retained the diagnosis at follow-up. Although subjects with aging-associated cognitive decline showed a reduced performance in all neuropsychological domains addressed, a significant decline was confined to delayed verbal memory test performance during the 4-year follow-up period in relation to comparison subjects. Aging-associated cognitive decline did not predict conversion to dementia during the follow-up interval. Conclusions: In young-old community-dwelling individuals, aging-associated cognitive decline is a frequent condition with a high temporal stability. During a 4-year follow-up, subjects with aging-associated cognitive decline deteriorated specifically in measures of episodic memory, underscoring the value of the respective deficits in characterizing "mild cognitive impairment."