Smoking can increase nasopharyngeal carcinoma risk by repeatedly reactivating Epstein-Barr Virus: An analysis of a prospective study in southern China

Background The association between smoking and nasopharyngeal carcinoma (NPC) is still uncertain. The aim of this study was to validate smoking effect on NPC and explore if smoking can induce NPC by persistently reactivating EBV in long-term based on a prospective cohort design. Methods A NPC screening cohort with 10 181 eligible residents in Sihui city, southern China was conducted from 2008 to 2015. The smoking habit was investigated through the trained interviewers and EBV antibodies (VCA-IgA, EBNA1-IgA) as screening markers were tested periodically. New NPC cases were identified through local cancer registry. Cox's regression model was used to estimate the adjusted hazard ratios (aHRs) of smoking on NPC incidence. In the non-NPC participants, the associations between smoking and EBV seropositivity in different periods were assessed by logistic regression and generalized estimating equations (GEE). Results With a median of 7.54 years, 71 NPCs were diagnosed >= 1 year after recruitment. Compared with never smokers, the aHRs of developing NPC among ever smokers were 3.00 (95%CI: 1.46-6.16). Stratified by sex, the HRs of ever smoking were 2.59 (95%CI: 1.07-6.23) for male and 3.75 (95%CI: 1.25-11.20) for female, respectively. Among the non-NPC individuals, ever smoking was not only associated with EBV seropositivity at baseline, but also in the 3-5 years of follow up, with adjusted odds ratios (aORs) of 1.68 (95%CI: 1.29-2.18) for VCA-IgA and 1.92 (95%CI: 1.42-2.59) for EBNA1-IgA. Among the smokers who were tested EBV antibodies at least twice, the similar results were obtained using GEE. Conclusion Smoking could significantly increase the long-term risk of NPC in southern China, partly by persistently reactivating EBV.