Abstract
BACKGROUND: Differential vulnerability to alcohol contributes to socioeconomic inequities in alcohol-attributable harm. This study aimed to estimate the sex-/gender-specific joint effects of socioeconomic position (SEP) and heavy episodic drinking or volume of alcohol use on 100% alcohol-attributable emergency department (ED) visits. METHODS: We conducted a cohort study among 36 900 men and 39 700 women current and former alcohol consumers aged 15-64 from population-representative Canadian Community Health Surveys (2003-2008) linked to administrative ED visit data through 2017 in Ontario and Alberta. We estimated sex-/gender-specific associations between SEP (both education and income) and heavy episodic drinking (≥5 standard drinks on one occasion, at least monthly) or volume of alcohol use (standard drinks per week) on incident alcohol-attributable ED visits and assessed additive interactions using the Synergy Index (S). RESULTS: Lower levels of education (eg, less than high school vs Bachelor's degree or above: men: adjusted HR (aHR)=3.71, 95% CI 2.47 to 5.58; women: aHR=1.75, 95% CI 1.15 to 2.68) and income (eg, quintile (Q)1 vs Q5, men: aHR=2.07, 95% CI 1.35 to 3.17; women: aHR=1.84, 95% CI 0.91 to 3.71) were associated with increased rates of alcohol-attributable ED visits. Among men and women, superadditive joint effects (ie, greater than the sum of both exposures experienced independently) were observed between low SEP (education and income) and heavy episodic drinking and higher volume of alcohol use on alcohol-attributable ED visits. INTERPRETATION: Our results indicate that individuals with lower SEP experience increased vulnerability to alcohol use and related harms. These findings highlight the urgent need for population-level interventions that reduce both the high burden and socioeconomic inequities in alcohol-attributable harm.