The Interactive Effect of Location, Alcohol Consumption and Non-Traffic Injury.

Aim This study aimed to assess the extent to which the association between recent alcohol consumption and risk of non-traffic injury varies according to location at the time of the injury. Design Case-cross-over design. Setting and participants A total of 15 625 injury patients from 49 emergency departments (EDs) in 22 countries. Measurements Recent alcohol consumption and location at the time of the injury were assessed for when the injury occurred and for the same time 1 week prior to this. The confounding and interactive effects of location were examined by estimating the adjusted odds ratio (OR) of injury from alcohol consumption adjusting for location and then by examining the alcohol consumption x location interaction. Findings There were significant interactive effects of location and alcohol consumption on injury risk. For example, the ORs for volume 0.1-3.0 drinks and street/public place each were 3.0 and 14.2, respectively, whereas the OR for their joint effect was 44.1, suggesting a positive additive interaction [relative excess risk due to interaction (RERI) = 27.9, P < 0.05] and zero multiplicative interaction (OR = 1.0, P = 0.895). The interactions of alcohol consumption with drinking establishment location, work-place and other locations were mostly additive and negative on the multiplicative scale (e.g. for interaction between volume 0.1-3.0 drinks and drinking establishment location: RERI = 1.19, P = 0.529; multiplicative interaction OR = 0.54, P < 0.05). Conclusions Location appears to influence the relationship between alcohol consumption and risk of injury. The association between alcohol consumption and injury appears to be greater in locations such as streets and public places compared with private residences.