Alcohol amount, drinking patterns, and gastric cancer risk: a nationwide study using targeted maximum likelihood...

Alcohol is a carcinogen; however, the risk associated with low-level drinking remains uncertain. We aimed to evaluate the associations of alcohol amount and drinking patterns with gastric cancer (GC) risk. We analyzed 6,007,469 Korean adults aged 50-69 who participated in the national health screening program in 2010-2011 and were followed for up to 10 years. Alcohol intake (g/day) was categorized as none, light, moderate, high, or heavy drinking. Targeted maximum likelihood estimation (TMLE) with Super Learner was applied to estimate risk ratios (RRs) for GC, adjusting for confounders selected using a directed acyclic graph. Drinking patterns were assessed based on drinking frequency, independent of total alcohol intake. GC risk increased progressively with higher alcohol intake, from light to heavy drinking, compared with that in non-drinkers, with the highest risk among heavy drinkers (5-year RR: 1.46; 95% CI: 1.41-1.51; 10-year RR: 1.43; 95% CI: 1.39-1.47). Even light drinking was associated with modest, significant increases in risk (5-year RR: 1.08; 95% confidence interval [CI]: 1.05-1.11; 10-year RR: 1.07; 95% CI: 1.04-1.10), although the low-level association was attenuated in a sensitivity analysis using an expanded adjustment set. Analyses incorporating repeated alcohol measurements from three time points yielded consistent results. Among light drinkers, associations were more pronounced among men and among former and current smokers. Consuming ≥ 1 drink per day was associated with higher GC risk than < 1 drink per day (5-year RR: 1.16; 95% CI: 1.12-1.19; 10-year RR: 1.19; 95% CI: 1.16-1.22). Within the same intake categories, individuals who drank more frequently showed higher GC risk than those with binge-type drinking patterns. These findings suggest that alcohol consumption is associated with increased GC risk in a dose-response manner. The association at low-level intake was modest and should be interpreted with caution, but these findings support recommendations to limit alcohol consumption for cancer prevention.