Prevalence of Aging-Associated Cognitive Decline - AACD in an Italian elderly population: results from the cross sectional phase of the Italian PRoject on the Epidemiology of Alzheimer's disease (I.PR.E.A.).

Background and aims: The prevalence of the preclinical phase of dementia varies greatly according to different diagnostic criteria and assessment procedures applied. The purpose of this study was to estimate the prevalence of cognitive impairment according to the Aging-Associated Cognitive Decline (AACD) diagnostic criteria in an Italian elderly population. Methods: In a multicenter community-based prospective study, 4785 Italian subjects aged 65-84 years, randomly selected from the registries of 12 Italian municipalities, were assessed by personal and informant interviews, physical and neurological examinations and an extensive neuropsychological battery. Results: Of these older subjects, 274 (9.2%) fulfilled all the AACD criteria, while 561 (18.8%) fulfilled only 3 of the 5 AACD criteria (AACD-3). When merging the two groups diagnosed according to the AACD criteria (AACD and AACD-3), the prevalence was 28.0% (28.3% for men and 27.6% for women). Furthermore, during analysis, other two groups of subjects were identified: a) Subjects with Objective evidence of Cognitive Decline without cognitive complaints (OCD), 508 (17.0%), i.e. subjects with documented neuropsychological deficits, but neither the subjects nor the informants reported cognitive complaints; and b) Subjects with Cognitive Complaints without objective demonstrable cognitive deficits (CC), 44 (1.5%), i.e. subjects and/or the informants reported cognitive complaints without evidence of neuropsychological deficits. Thus, taking into consideration the additional OCD group, a total of 1,343 persons with cognitive impairment without dementia (45.0%) was identified. Conclusions: On the basis of our results, we estimated that 45% of our population-based Italian sample aged 65-84 years had some kind of cognitive deficits without dementia.