Mohammed T. Abou-Saleh

CASE-CONTROL STUDIES 201528 incident dementia cases and 28 768 person-years of follow-up.As a common core, each study included a population-basedcohort of persons aged 65 years and older living in the communityand nursing homes. Samples were drawn from defined geographicareas and either include all eligible individuals or individualsrandomly selected within predefined strata. All studies contributedto the pooled analyses baseline data and one follow-up panelconducted after a fixed interval of about 3 years. The cohortsexclude the prevalent cases identified at baseline.Dementia cases were identified in a two-stage procedure,whereby the total cohort was screened and screen-positive subjectsunderwent a detailed diagnostic assessment that included aclinical exam, neuropsychological testing and an informantinterview. Dementia and vascular dementia were diagnosedaccording to DSM-III-R criteria 8 , Alzheimer’s disease (AD) wasdiagnosed according to NINCDS–ADRDA criteria 9 .RESULTSAD comprised approximately 70% of all cases. Incident rates fordementia and AD were similar across studies. There was anincrease with age in the incidence of all dementia and in particularAD. At 90 years of age and older the incidence of AD was 63.5(95% CI, 49.7–81.0) per 1000 person-years. However, comparedto men, women had significantly higher rates of AD after age 85years. At 90 years of age, the rate of AD per 1000 person-yearswas 81.7 (63.8–104.7) in women and 24.0 (10.3–55.6) in men(Figure 1a,b) 10 . This translated into a cumulative risk for 65 yearoldwomen to develop AD at the age of 95 years of 0.22 comparedto 0.09 for men. These sex differences were not found in vascularAPerson-yearsBPerson-years10090807060504030201001009080706050403020100MenWomenDementiaADVDDementiaFigure 1 Incidence of dementia and major sub-types, Alzheimer’s disease(AD) and vascular dementia (VD): EURODEM Studies. (A) men; (B)womenADVDdementia: at 90 years of age, the incidence of vascular dementiawas 15.9 (6.6–38.5) and 9.2 (4.3–19.6) per 1000 person-years inmen and women, respectively.In addition to sex and age, we investigated the association ofAD to four risk factors that had been previously investigated incase-control studies 1,2 . These risk factors were ascertained in asimilar manner across studies. We found that low educationincreased the risk for dementia, specifically AD. However, theincreased risk was detectable only in women: compared to thosewith high education, those with low education had a 4.3 (95% CI,1.5–11.9) times, and those with middle education had a 2.6 (95%CI, 1.0–7.1) times increased risk for AD. There was no associationof educational level to dementia among men 11 . Contrary to aprevious EURODEM analysis based on case-control studies 2 ,wedid not find an increased risk for AD associated with headtrauma. Previous reports based on prevalent cases suggested aninverse association of smoking with the risk for AD 2 . In thesecurrent analyses based on incident cases, we found currentsmoking significantly increased the risk of AD. The risk associatedwith smoking was higher in men than women 1 . Finally, we foundthat the association of AD to family history in two or more familymembers was weaker (OR 1.59 95% CI, 0.78–3.26) thanpreviously estimated on the basis of case-control studies 2 .SUMMARYBecause we had a large sample, we were able to investigatewhether gender modified the risk for AD, the most common formof late-life dementia. 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