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Background and Aim: Helicobacter pylori (H. pylori) infection rates have been changing with different populations and geographic areas. We systematically evaluated the longitudinal trends in H. pylori prevalence in China over the past decades. Methods: We performed a systematic review of literature reporting the prevalence of H. pylori infection in mainland China from 1990 to 2019 in the PubMed and China National Knowledge Infrastructure databases. We conducted a meta‐analysis of qualified studies using a random effects model to estimate the pooled prevalence with a 95% confidence interval (95%CI). Results: A total of 412 eligible studies with 1 377 349 subjects were included. The pooled H. pylori prevalence was 44.2% (95%CI: 43.0–45.5%) in mainland China, with an estimated 589 million individuals infected with H. pylori. The prevalence was relatively high in the Northwest (51.8%, 95%CI: 47.5–56.1%), East (47.7%, 95%CI: 45.4–50.0%), and Southwest China (46.6%, 95%CI: 42.1–51.1%). The prevalence significantly decreased from 58.3% (95%CI: 50.7–65.5%) in the period 1983–1994 to 40.0% (95%CI: 38.2–41.8%) in the period 2015–2019. The prevalence increased with age, ranging from 28.0% (95%CI: 23.9–32.5%) in children and adolescents to 46.1% (95%CI: 44.5–47.6%) in adults. Conclusion: Although the burden of H. pylori infections is still huge in China, the infection rate has been decreasing over the past decades. Targeted H. pylori eradication strategies may be considered in areas or populations with a high incidence of gastric cancer. [ABSTRACT FROM AUTHOR]

Background: Genetic variants and lifestyle factors have been associated with gastric cancer risk, but the extent to which an increased genetic risk can be offset by a healthy lifestyle remains unknown. We aimed to establish a genetic risk model for gastric cancer and assess the benefits of adhering to a healthy lifestyle in individuals with a high genetic risk.Methods: In this meta-analysis and prospective cohort study, we first did a fixed-effects meta-analysis of the association between genetic variants and gastric cancer in six independent genome-wide association studies (GWAS) with a case-control study design. These GWAS comprised 21 168 Han Chinese individuals, of whom 10 254 had gastric cancer and 10 914 geographically matched controls did not. Using summary statistics from the meta-analysis, we constructed five polygenic risk scores in a range of thresholds (p=5 × 10-4 p=5 × 10-5 p=5 × 10-6 p=5 × 10-7, and p=5 × 10-8) for gastric cancer. We then applied these scores to an independent, prospective, nationwide cohort of 100 220 individuals from the China Kadoorie Biobank (CKB), with more than 10 years of follow-up. The relative and absolute risk of incident gastric cancer associated with healthy lifestyle factors (defined as not smoking, never consuming alcohol, the low consumption of preserved foods, and the frequent intake of fresh fruits and vegetables), was assessed and stratified by genetic risk (low [quintile 1 of the polygenic risk score], intermediate [quintile 2-4 of the polygenic risk score], and high [quintile 5 of the polygenic risk score]). Individuals with a favourable lifestyle were considered as those who adopted all four healthy lifestyle factors, those with an intermediate lifestyle adopted two or three factors, and those with an unfavourable lifestyle adopted none or one factor.Findings: The polygenic risk score derived from 112 single-nucleotide polymorphisms (p<5 × 10-5) showed the strongest association with gastric cancer risk (p=7·56 × 10-10). When this polygenic risk score was applied to the CKB cohort, we found that there was a significant increase in the relative risk of incident gastric cancer across the quintiles of the polygenic risk score (ptrend<0·0001). Compared with individuals who had a low genetic risk, those with an intermediate genetic risk (hazard ratio [HR] 1·54 [95% CI 1·22-1·94], p=2·67 × 10-4) and a high genetic risk (2·08 [1·61-2·69], p<0·0001) had a greater risk of gastric cancer. A similar increase in the relative risk of incident gastric cancer was observed across the lifestyle categories (ptrend<0·0001), with a higher risk of gastric cancer in those with an unfavourable lifestyle than those with a favourable lifestyle (2·03 [1·46-2·83], p<0·0001). Participants with a high genetic risk and a favourable lifestyle had a lower risk of gastric cancer than those with a high genetic risk and an unfavourable lifestyle (0·53 [0·29-0·99], p=0·048), with an absolute risk reduction of 1·12% (95% CI 0·62-1·56).Interpretation: Chinese individuals at an increased risk of incident gastric cancer could be identified by use of our newly developed polygenic risk score. Compared with individuals at a high genetic risk who adopt an unhealthy lifestyle, those who adopt a healthy lifestyle could substantially reduce their risk of incident gastric cancer.Funding: National Key R&D Program of China, National Natural Science Foundation of China, 333 High-Level Talents Cultivation Project of Jiangsu Province, and China Postdoctoral Science Foundation. [ABSTRACT FROM AUTHOR]