Gastric Cancer Incidence After Helicobacter pylori Eradication and Lifestyle‐Related Risk Factors: A Population‐Based Cohort Study

Backgrounds Although Helicobacter pylori (Hp) eradication reduces gastric cancer (GC) risk, GC still develops in some patients after successful eradication. Population‐based data on post‐eradication GC incidence and lifestyle‐related risk factors remain limited. This study aimed to assess GC incidence after Hp eradication and to identify associated lifestyle factors in a nationwide cohort. Materials and Methods We conducted a retrospective cohort study using Japanese healthcare insurance claims and medical check‐up data from 2014 to 2023. Patients who have successfully eradicated Hp were included. GC development 1 year or more after eradication was the primary outcome. The follow‐up period extended from 1 year after the initiation of eradication medication until the final insurance record, GC development, or death. GC incidence and risk factors were evaluated using Kaplan–Meier analysis and Cox proportional hazards models adjusted for age and sex. Results Among 59,274 patients (mean age 64.9 years; 44.6% male), 649 (1.44%) developed GC during a mean follow‐up of 3.66 years, with a cumulative incidence of 1.47% at 5 years. Male and older age at the Hp eradication was significantly associated with increased GC incidence ( p < 0.001, 1og‐rank test). Among various lifestyle factors, only smoking was independently associated with GC risk (adjusted hazard ratio (aHR) 1.37, 95% Confidence Intervals (CI) 1.05–1.78). Everyday alcohol consumption in the current smokers is associated with GC risk (aHR 1.80, 95% CI 1.22–2.66), compared with non‐smokers/drinkers. Conclusion GC remains a clinically important outcome even after Hp eradication. Smoking was associated with a higher risk of post‐eradicated GC, and smoking cessation may contribute to risk reduction in this population. These findings suggest that lifestyle factors, together with host characteristics such as age, male sex, and alcohol consumption, may be considered when designing risk‐stratified surveillance strategies.