The Joint Effect of Education and Alcohol Use on 100% Alcohol-attributable Hospitalization or Death in Canada.

Background: Individuals with low socioeconomic position (SEP) experience disproportionately greater alcohol-attributable harm than individuals with high SEP despite similar or less alcohol use (i.e., the alcohol harm paradox). We examined the sex/gender- specific independent and joint effects of education and heavy drinking or volume of alcohol use on 100% alcohol-attributable hospitalization or death.

Methods: We conducted a cohort study among 199,125 current and former alcohol users aged 15-64 years from population-representative Canadian Community Health Surveys (2000-2008) linked to hospitalization and mortality records through 2017. We estimated the sex/gender-specific associations between education and heavy drinking or volume of alcohol use and incident 100% alcohol-attributable hospitalization or death using multivariable Fine and Gray subdistribution hazard models with competing risk (non-100% alcohol-attributable deaths), assessing additive interactions using the Synergy Index (S).

Results: Overall, heavy drinking prevalence and volume of alcohol use were similar or lower in individuals with lower education compared with higher education. Lower education levels compared with a bachelor's degree or above were associated with increased 100% alcohol-attributable hospitalization or death [e.g., less than high school, men: hazard ratio (HR) = 2.78; 95% CI = 2.17, 3.56; women: HR = 2.98; 95% CI = 2.00, 4.44]. We found superadditive joint effects between low education and heavy drinking (men: S = 1.22; 95% CI = 1.14, 1.30; women: S = 1.34; 95% CI = 0.88, 2.04) and low education and higher volume of alcohol use (e.g., excess volume, men: S = 1.30; 95% CI = 1.05, 1.62; women: S = 1.41; 95% CI = 0.77, 2.58), with larger inequities in women than men with similar alcohol use.

Conclusions: Our study is consistent with the hypothesis that increased vulnerability to alcohol use among individuals with lower education partially explains the alcohol harm paradox in Canada.