Gao S, et al. - In order to determine shifts in incidence rates of dementia and Alzheimer disease (AD) over time, researchers analyzed published studies that described age-specific incidence rates of dementia and AD. The included studies were identified from PubMed and MEDLINE. A total of 38 articles with 53 cohorts on dementia incidence and 31 articles with 35 cohorts on AD incidence were eligible. Across all three age groups (65-74, 75-84, and 85 years and older), significant links between later birth years and reduced dementia incidence rates were reported, while no significant links between birth year and AD incident rates were evident in any of the three age groups. In all age groups, incidence rates for AD from Western countries remained steady. AD incidence rates increased significantly for the 65- 74 years age group in non-Western countries, but a nonsignificant link was reported for the 75-84 or 85 years and older groups. Overall, a fall in dementia incidence was noted over the past four decades, but no reduction was evident in AD incidence.