Relative risk of injury from acute alcohol consumption: modeling the dose-response relationship in emergency department data from 18 countries.

AIMS: To update and extend analysis of the dose-response relationship of injury and drinking by demographic and injury subgroups and country-level drinking pattern, and examine the validity and efficiency of the fractional polynomial approach to modeling this relationship.
DESIGN: Pair-matched case-cross-over analysis of drinking prior to injury, using categorical step-function and fractional polynomial analysis.
SETTING: Thirty-seven emergency departments (EDs) across 18 countries. PARTICIPANTS: A total of 13 119 injured drinkers arriving at the ED within 6 hours of the event. MEASUREMENTS: The dose-response relationship was analyzed by gender, age, cause of injury (traffic, violence, fall, other) and country detrimental drinking pattern (DDP).
FINDINGS: Estimated risks were similar between the two analytical methods, with injury risk doubling at one drink [odds ratio (OR) = 2.3-2.7] and peaking at about 30 drinks. Although risk was similar for males and females up to three drinks (OR = 4.6), it appeared to increase more rapidly for females and was significantly higher starting from 20 drinks [female OR = 28.6; confidence interval (CI) = 16.8, 48.9; male OR = 12.8; CI = 10.1, 16.3]. No significant differences were found across age groups. Risk was significantly higher for violence-related injury than for other causes across the volume range. Risk was also higher at all volumes for DDP-3 compared with DDP-2 countries.
CONCLUSIONS: There is an increasing risk relationship between alcohol and injury but risk is not uniform across gender, cause of injury or country drinking pattern. The fractional polynomial approach is a valid and efficient approach for modeling the alcohol injury risk relationship.