Gender differences in predrinking behavior among nightclubs' patrons

Background<br/>Drinking before entering nightclubs (predrinking) seems to be associated with an increase in alcohol-related harm. This study aims to investigate gender differences in predrinking behavior and to evaluate its association with risk behaviors practiced inside nightclubs.<br/><br/>Methods<br/>Individual-level data were collected by a portal survey of 2,422 patrons at the entrance and 1,833 patrons at the exit of 31 nightclubs located at Sao Paulo, Brazil. The nightclubs were selected by 2-stage sampling with probability proportional to the establishments capacity in the first stage and a systematic sample of patrons in the entrance line in the second stage. Breath alcohol concentration (BrAC) was measured at the entrance and exit. Face-to-face interviews identified predrinking characteristics and risk behaviors. Weighted analyses were stratified by gender.<br/><br/>Results<br/>Predrinking was practiced by 49.2% (95% confidence interval [CI] = 42.7 to 55.8) of the male patrons and 29.0% (95% CI = 20.6 to 38.9) of the female patrons (p < 0.001) on the day of the interview. When considering only predrinkers, men and women showed similar BrAC at entrance and exit and similar proportion of alcoholic intoxication (BrAC = 0.38 mg/l). In both genders, people who practiced predrinking on the day of the interview were more likely to drink inside the nightclub, compared to those who did not practice predrinking (p < 0.001). Among men, the practice of predrinking increased the chance of drinking and driving after leaving the nightclub (odds ratio [OR] = 6.9, 95% CI = 4.1 to 11.5, p < 0.001). Among women, the practice of predrinking increased the chances of experiencing sexual harassment in the nightclub (OR = 2.9, 95% CI = 1.3 to 6.6, p = 0.010).<br/><br/>Conclusions<br/>Predrinking is more prevalent among men; however, men and women who engaged in predrinking have a similar pattern of alcohol consumption and exit BrAC. The fact that risk behaviors and illicit drug use were associated with predrinking but differ between genders suggests that a gender-specific approach should be used in tailored interventions to prevent alcohol-related harm in nightclubs.