Sex differences in acute tolerance to the objective and subjective effects of alcohol.

Alcohol is well known for impairing motor coordination and increasing subjective intoxication. Previous research has found that these effects are exacerbated in women, but such observations were limited to times when blood alcohol concentrations (BACs) were at or near peak. Interestingly, alcohol-induced impairment of motor coordination and subjective intoxication both demonstrate acute tolerance, meaning they recover faster than the decline of BAC as alcohol is eliminated. Consideration of acute tolerance to both measures in tandem is particularly important because if recovery from subjective intoxication outpaces recovery from objective motor impairment, a drinker may develop a false sense of freedom from the impairing effects of alcohol. Such a misjudgment can lead the drinker to engage in risky behavior as BAC declines. The present study examined whether sex differences were present in the acute tolerance to motor impairment and subjective intoxication. Twenty-five women and 25 men participated in a placebo-controlled study of their acute tolerance to motor impairment and subjective intoxication following a moderate dose of alcohol, 0.60 g/kg for women and 0.64 g/kg for men. Repeated assessments of motor coordination with a grooved pegboard and subjective intoxication with a visual analog scale were conducted seven times as BAC declined. While all participants demonstrated acute tolerance to both motor impairment and subjective intoxication, women exhibited significantly faster recovery from subjective intoxication than men. Consequently, women may be more likely than men to engage in risky behavior on the descending limb, such as alcohol-impaired driving.