Occurrence of Cognitive Impairment and Dementia after the Age of 60: A Population-Based Study from Northern Italy

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Abstract
To evaluate the age, gender and education distribution of both cognitive impairment and dementia in the whole old age range of the elderly (from 61 years of age and over). The study population consisted of all subjects born in 1930 or before, living in the municipality of Faenza and Granarolo, Italy (n = 7,930). A two-phase study design was implemented, by using the Mini-Mental State Examination and Global Deterioration Scale as screening instruments. The DSM-III-R diagnostic criteria were used for the clinical diagnosis of dementia. A subject was classified as affected by cognitive impairment, no dementia (CIND) if he/she scored 2 or more standard deviations lower than the corrected mean MMSE score. The prevalences of dementia and CIND were 6.5 per 100 (95% CI 5.9-7.0) and 5.1 per 100 (95% CI 4.6-5.6), respectively. The prevalence of CIND was higher than that of dementia in the youngest old groups (61-74 years), both in men and women, whereas the opposite pattern was present among the older old (75+). In the older age groups, dementia prevalence increased exponentially with age, while CIND prevalence was more stable. There was not a substantial gender difference in CIND prevalence in all ages. Only in the subpopulation of higher educated subjects, women had a higher prevalence of both dementia and CIND than men. Lower educated subjects had a higher prevalence of both dementia and CIND. When compared to higher educated persons, subjects without any schooling had odds ratios of 10.9 (CI 7.0-16.7) and 16.7 (CI 11.2-25.0) for dementia and CIND, respectively. Cognitive impairment is very common in the younger old ages (under 70 years of age), whereas dementia becomes predominant after 75 years of age. Both conditions are strongly related to the educational level.