The joint association of average volume of alcohol and binge drinking with hazardous driving behaviour and traffic crashes.

Background: Previous studies on alcohol-related road safety have not assessed the joint impact of average volume of alcohol and binge drinking.

Objective: To examine the joint and separate association of average volume of alcohol and binge drinking with hazardous driving behaviour and traffic crashes.

Methods: Data were drawn from telephone interviews conducted in the period 2000-2005, with 12 037 individuals representative of the population aged 18-64 years in the Madrid region, Spain. The threshold between average moderate and heavy volumes was 40 g of alcohol/day in men and 24 g/day in women. Binge drinking was defined as intake of >or= 80 g of alcohol in men and >or= 60 g in women, during any drinking occasion in the preceding 30 days. Individuals were classified into the following categories: (i) non-drinkers; (ii) moderate drinkers with no binge drinking (MDNB); (iii) moderate drinkers with binge drinking (MDB); (iv) heavy drinkers with no binge drinking (HDNB); and (v) heavy drinkers with binge drinking (HDB). Analyses were performed using logistic regression, with adjustment for sex, age and educational level.

Results: Frequency of inadequate seat-belt use increased progressively across categories of alcohol consumption, with odds ratio (OR) 1 in non-drinkers, 1.19 [95% confidence interval (CI) 1.06-1.33] in MDNB, 1.69 (1.41-2.03) in MDB, 1.68 (1.24-2.29) in HDNB and 2.41 (1.83-3.18) in HDB (P for trend <0.001). Compared with MDNB, alcohol-impaired driving was also more frequent in MDB (OR 7.43; 95% CI: 5.52-10.00), HDNB (OR 7.31; 95% CI: 4.37-12.25) and in HDB (OR 15.50; 95% CI: 10.62-22.61). Lastly, compared with non-drinkers, frequency of traffic crashes increased progressively across categories of alcohol consumption (P for trend=0.028), although it only reached statistical significance in HDB (OR 2.01; 95% CI: 1.00-4.09).

Conclusions: Self-reported average volume of alcohol and binge drinking are both associated with self-reported hazardous driving behaviour and traffic crashes. The strength of the association is greater when average heavy consumption and binge drinking occur jointly.