The mean AUDIT-C was age adjusted for comparison with the trajectories. To compute the age-adjusted mean AUDIT-C score, we used age 50 as the reference point and created weights to down-weight scores for individuals younger than 50 and up-weight scores for individuals older than 50. To create the weights, we first calculated the mean AUDIT-C score at each age (e.g., average score of all 22-year-olds, average score of all 23-year-olds). The mean score at age 50 was then divided by each age-specific mean to create the weights (e.g., mean at age 50/mean at age 22=weight for age 22). Then, the subject-specific AUDIT-C scores were multiplied by the appropriate weight (e.g., an AUDIT-C score for an individual at age 30 was multiplied by the corresponding weight for age 30). The weighted scores for a participant were summed and divided by the sum of the weights used for that participant to calculate the age-adjusted mean AUDIT-C score. The mean scores were rounded to the nearest whole from 0–12 and higher scores were collapsed due to their relatively small sample sizes. This resulted
