Objective: To compare the prevalence of dementia in two different time periods and two different studies.
Method: Representative, random samples of the elderly (>65 years) in the Zaragoza Study or ZARADEMP-0 (n = 1080) completed the previous decade, and now in Wave I of the ZARADEMP Project or ZARADEMP-I (n = 3715) were interviewed. Standardized measures included the Geriatric Mental State and the History and Aetiology schedule. Cases of dementia were diagnosed according to DSM-IV criteria.
Results: Adjusted, global prevalence of dementia has not varied significantly: it was 5.2% (95% CI = 3.9-6.6) in ZARADEMP-0 and 3.9% (95% CI = 3.3-4.5) in ZARADEMP-I (prevalence ratio = 0.75; 95% CI = 0.56-1.02). However, the prevalence in ZARADEMP-I was significantly lower among men, particularly in all age groups between 70 and 84 years.
Conclusion: Stability of the global prevalence of dementia in the elderly population has been documented. However, the decreased prevalence found in elderly men stimulated environmental hypotheses.