The characteristics of the samples are given in Table 1. Relative to the NHIS sample, the VA sample had a higher mortality rate, and more individuals with medical comorbidity. This is consistent with what would be expected for the difference between an epidemiological sample (NHIS) and a clinic-based sample (VA). In addition, the VA sample had a shorter follow-up period with less variability, more men, more African Americans, and fewer Hispanics. Of note, the VA sample had a lower proportion of current drinkers, which would be expected for an older sample with increased medical comorbidity.
