PBA Home > Institutional Research & Analysis > Surveys > Client-Requested > College Alcohol Study > Blood alcohol content

1999 College Alcohol Study
Blood Alcohol Content of Binge Drinkers

Binge drinking has been defined as 4 or more drinks in a row for women, and 5 or more drinks in a row for men (Wechsler, Dowdall, Davenport, Rimm; 1995). Some argue that this is an unfair definition of binge drinking because it does not take into account other variables that affect blood alcohol content levels (e.g., the amount of time in which the drinks were consumed, body weight, and gender), and therefore, could potentially overestimate the number of students engaging in high-risk drinking.

Using the data from the 1999 College Alcohol Study, it is possible to estimate the average blood alcohol content (BAC) for students the last time they binge drank according to this definition. By examining BAC it is possible to obtain a better understanding of the level of intoxication the average binge drinking student reaches.

BAC Levels for Binge Drinkers

The College Alcohol Study survey asks those students who had four or more drinks in a row how many drinks they had had the last time they did so, and how long it took to consume those drinks. Gender and weight are also obtained. We used this information to calculate each student's BAC (see below for method of BAC calculation).

The average BAC for men who binged (those who reported 5 or more drinks) was .15 the last time they binged. For women who binged (those who reported 4 or more drinks) the average BAC was .18 the last time they did so. Of those who binged, 86% of men and 94% of women achieved a BAC of .08 or higher the last time they binged.

Clearly, the majority of students classified as binge drinkers are becoming intoxicated when they drink at that level. However, it should be noted that especially for men, setting 5 or more drinks as the criterion for binge drinking does overestimate intoxication for this group; 14% did not reach the legal BAC level for impairment.

Conclusion

BAC's at these levels are well above the legal limit and are indicative of serious impairment in physical and mental functioning. (It is important to remember that this is not the average BAC of students who drink alcohol in general, but instead the BAC of students who binge drink according to the definition used by the College Alcohol Study.) It is clear from these averages, that the overwhelming majority of students who binge drink are reaching quite high levels of intoxication and are potenitally placing themselves in harms way as a result of their drinking.

BAC Calculation

The College Alcohol Study survey asked those students who had four or more drinks in a row how many drinks they had had the last time they did so, and how long it took to consume those drinks. Gender and weight were also obtained. We used this information to calculate each student's BAC.

Many variables go into the formula for calculating BAC, including several that vary from person to person such as metabolic rate and percent of the body that holds alcohol. Because these factors are extremely individual, constants are often substituted into the formula for BAC which assume the average values for men and women. In this case the following constants were used: percent of body that holds alcohol (68% for men and 55% for women), metabolic rate (.017/hour), fluid ounces of alcohol per drink (.54 fl. oz., which is equivalent to a 12 oz. beer with 4.5% alcohol content), weight of each fluid ounce of alcohol in pounds (.0514lb./fl.oz.), and the specific gravity of blood (1.055g/ml). In addition to the constants, to determine BAC the following information is necessary: number of drinks consumed, gender, weight, and hours since first drink. The formula (after multiplying several of the constants for simplification) is:

(# of drinks x .54) x (8 or 10)^* / Pounds of person - (Hours since first drink x .017)

^* Use 8 for a man, 10 for a woman

Note: The last category on the CAS survey for hours to consume drinks is "6 or more hours." This formula may overestimate BAC for the very few cases that consumed more than 10 drinks, but did so in 6 or more hours if they actually consumed the drinks at a rate of about 1-2 per hour

College Alcohol Study Main Page

Last revision 07/08/05