Retention rates were very high in this study, with 1506 of a possible 1520 quarterly follow-ups (99.1%) completed. One male LD withdrew from the study without specifying the reason during the second year of follow-up. No other participants withdrew or were lost to contact during the 2-year interval. We imputed missing data (0.9%) by taking the average of values from the 2 surrounding follow-ups or the last observation carried forward, as warranted. During the 2 years of follow-up, drinking rates remained significantly different between the groups: LD consumed alcohol on 23% (range, 2%–62%) of days, whereas the HD consumed alcohol on 46% (range, 9%–89%) of days (P<.001), and LD engaged in binge drinking on 1.4% (range, 0%–8%) of days compared with 26% (range, 3%–54%) of days for HD (P<.001).
