Comparing high-risk drinking measures and estimated BAC levels as predictors of negative consequences in a state-wide survey of young adults

Survey research on young adults commonly uses 5 or more drinks at a sitting (or 4 or more drinks at a sitting for women) as an indicator of high risk drinking. For a more precise measure of impairment and presumed risk, it is also possible to compute estimated blood alcohol concentration (BAC) levels achieved in drinking occasions from survey reports using calculations that include time, body characteristics, and other background information about drinking patterns. Data in this study are drawn from two anonymous random sample surveys of 18 to 24 year old Montana adults conducted in 2000-2001 using the same survey measures (combined N=1449). Previous research has identified weight, height, age, and sex to be most significant in determining BAC levels. In addition, alcohol clearance rates vary by drinking history of individuals. The current research constructed several methods of BAC estimation incorporating these variables along with quantity measures and time period measures from the survey of young adults. Each measure estimating BAC level along with more simplified measures of high risk consumption are evaluated in terms of accuracy in predicting negative consequences that respondents also reported in the survey. Thus this study evaluates the added value of using various BAC estimates when attempting to identify risking drinking among young adults with diverse biological and social characteristics. The study also evaluates BAC estimates assuming "front loading" or heavier consumption in the first half of a drinking episode and reports the comparative value of this method in predicting negative consequences.