communities (N=5,888 including 4,925 whites). The baseline examination was either in 1989–90 or 1992–93.13 The FHS is a U.S.-based single-site study that comprises 3 generations of participants. Members of the Original cohort followed since 1948 (N=5,209)14,15 and the Offspring cohort followed since 1971 (N=5,124),14 were invited to undergo an initial brain MRI in 1999–2005. The Rotterdam Study enrolled inhabitants from a district of Rotterdam (Ommoord), The Netherlands, aged 55 years or older (N=7,983) at the baseline examination in 1990–93 (Rotterdam Study I).16 In 2001, the Rotterdam Study cohort was expanded by 3,011 newly eligible persons (Rotterdam Study II).
