Risk of injury from acute alcohol consumption and the influence of confounders

Abstract

Aim: To quantify the relationship between acute alcohol consumption and risk of injury, in the context of other potential confounding factors (i.e. usual alcohol intake, risk-taking behaviour and substance use-defined as prescription/over-the-counter medication or illicit substances), using three separate measures of alcohol consumption.

Design: A hospital-based, case-control study.

Setting: The accident and emergency department at a large metropolitan teaching hospital in Queensland, Australia.

Participants: Four hundred and eighty-eight cases were matched to 488 population controls on gender, age group, neighbourhood, day and time of injury.

Measurements: Risk factor and injury information was obtained by questionnaire and medical record review.

Results: After controlling for demographic and situational variables (i.e. activity, location and companions at time of injury), consuming any alcohol in the 6 hours prior to time of injury significantly increased risk of injury [odds ratio (OR) = 2.13, 95% confidence interval (CI): 1.3-3.9]. Drinking at levels above low-risk guidelines for short-term health (i.e. drinking > 40 g alcohol per occasion if female, and drinking > 60 g alcohol if male) increased injury risk by a factor of almost 2.5 (OR = 2.41; 95% CI = 1.1-5.2). Finally, drinking beer (OR = 1.86; 95% CI = 0.9-3.9), spirits (OR = 3.05; 95% CI = 1.1-8.2) or a combination of beverages (OR = 3.16; 95% CI = 1.1-8.8) increased risk of injury. When usual alcohol consumption patterns were adjusted for, substantial increases in the alcohol-injury odds ratios were observed for all measures of alcohol. When risk-taking behaviour and substance use were considered, changes in the effect of alcohol on injury risk were observed, for all measures of alcohol. These data support the hypotheses that some confounding exists in the alcohol-injury relationship due to usual drinking patterns, risk-taking and substance use.

Conclusions: In this study, acute alcohol consumption significantly increased the risk of injury, even when situational and other risk factors were considered. However, the relationship between alcohol and injury appears confounded by usual drinking patterns, risk-taking behaviour and substance use. Therefore, these variables should be considered in any analysis of the alcohol-injury relationship, and also considered when developing public health strategies to reduce alcohol-related injury. Further research is required to elucidate the nature of this relationship, and to identify the effect of risk-taking and substance use on different types of injuries (e.g. mechanism of injury; body region injured) and injury severity. The stability of the models and the consistency of the findings across all measures of alcohol used support claims for the validity of the observed effects.