Our analytic strategy sought to minimize the possibility that the observed effects of alcohol on mortality are due to confounding. All analyses were adjusted for age, gender, race, comorbidity, drinking quantity, and binge drinking frequency. In addition, we adjusted for smoking status in the NHIS sample (smoking status was not available in the VA sample). Finally, we repeated the analyses in the NHIS subset of never smokers. Because the findings were robust across analyses, the observed associations are unlikely to be due to these potential confounders. However, other unmeasured confounders may have influenced the results. For example, psychosocial stressors that may disproportionately and adversely affect individuals of low socioeconomic status may negatively affect health outcomes. Therefore, the inability to adjust for these factors may bias the results. In addition, the VA sample had a higher proportion of individuals with comorbidities, and because some of them may have reduced drinking after development of certain illnesses, the inability to differentiate former drinkers from lifetime abstainers is important to note.
