Longitudinal observation of a general population sample with subclinical cognitive deficits has demonstrated multiple patterns of cognitive change with variable clinical outcomes including dementia, depression, cardiovascular disease, and respiratory disorders.1 However, the identification of those cases likely to evolve towards dementia has been given priority, especially Inhibitors,research,lifescience,medical given the development of treatments that may delay dementia onset. The potential treatment window for

dementia is large, with twin studies indicating that insidious changes in cognitive performance may occur up to 20 years before VX-689 in vivo disease onset.2 Population studies allow us to develop models of disease etiology within this more complex multifactor setting. Figure 1. Mild cognitive impairment has multiple interacting causes. CNS, central nervous system. Epidemiology Inhibitors,research,lifescience,medical has a triple role in terms of public health: Descriptive epidemiology: the monitoring of disease prevalence and incidence across time. Analytical epidemiology: Inhibitors,research,lifescience,medical the determination of risk factors and their patterns of interaction, permitting the construction of hypothetical etiological models

of disease processes. Interventional epidemiology: the designation of potential intervention points for the reduction of morbidity and mortality, which may guide more targeted clinical research. MCI will be discussed here in relation to these three functions. Descriptive epidemiology of MCI The emergence of MCI as a health problem and the expansion of cognitive morbidity at a population level are clearly related to the general phenomenon of population aging. As Gruenberg3 pointed out in

1977, it is one of Inhibitors,research,lifescience,medical the “failures of success” that, while medical research has reduced the mortality of disease, it has concurrently extended life expectancy and increased the proportion of persons in the Inhibitors,research,lifescience,medical community with chronic pathologies. Analyses of longitudinal health survey data from the USA by Kramer4 in the early 1980s provided early empirical evidence of the rapid expansion of dependency due to cognitive disorders arising from increases in disease incidence, better management of its physiological consequences, and thus decreased direct mortality This public health dilemma was, in fact, predicted by Jonathan CYTH4 Swift in the early 18th century In Gulliver’s Travels,5 he described the cognitive consequences of extended longevity in eternal beings, who, on reaching the age of 80 and in the absence of degenerative disease, continue to perform daily activities but have difficulty in recalling the names of common objects and recently read material, forget the name of friends, and consequently have diminished pleasure in life. It is a description that comes quite close to current definitions of MCI, and distinguishes MCI from normal aging and dementia.