VETSA

VETSA is a longitudinal behavioral genetic study of cognitive and brain aging in men, run from the University of California San Diego with a second site at Boston University. Its participants are twins from the Vietnam Era Twin Registry who were all in their 50s when first assessed, so the cohort follows a narrow age band from midlife into early old age. A companion MRI project scans a subset of the twins at each wave, and the imaging has been used mainly for heritability studies of cortical and subcortical brain structure. Non-imaging data from waves 1 to 3 are archived at NACDA (ICPSR study 38836); other data, including the scans, are requested from the study team.

Composition

Wave 1 ran from 2003 to 2007 with 1,237 twins (349 monozygotic pairs, 265 dizygotic pairs, 9 unpaired). Of these, 526 had structural MRI at wave 1, and in 2012 these twins were getting a second scan at the 5-year follow-up. All participants are men who served in the US military between 1965 and 1975; most were not in combat. The 474 wave 1 MRI participants analysed by Kremen et al. (2010) were 51 to 59 years old (mean 55.8) and included 110 monozygotic and 92 dizygotic complete pairs.

Acquisition

Wave 1 scans were acquired on Siemens 1.5 T scanners at UC San Diego and Massachusetts General Hospital, with two sagittal T1-weighted MPRAGE volumes per session (voxel size 1.3 x 1.0 x 1.3 mm). The two volumes were corrected for gradient nonlinearity and B1 inhomogeneity, averaged and processed with FreeSurfer using a study-specific training atlas. From wave 2 the protocol adds resting-state functional MRI of the default mode network and arterial spin labeling.

Known limitations

• Men only, from a single birth cohort of veterans.
• No public download of the images. Access depends on an approved request and a signed agreement.
• The MRI paper gives 231 Boston participants in one place and 233 in another. Counts and scanner details for later waves are not published on the official pages read for this entry.