Risk factors for nasopharyngeal carcinoma.

In an effort to assess the relative importance of various risk factors of nasopharyngeal carcinoma (NPC), which includes antibodies to Epstein-Barr virus capsid antigen (anti-VCA) and early antigen (anti-EA) as well as other environmental factors, a multivariate logistic regression method was applied to analyze previously collected data from an epidemiologic study on 343 cases with NPC and 1017 neighborhood controls. Anti-VCA and anti-EA titers were found significantly associated with NPC. The relative risk increased with the increase of antibody titers. Individuals who smoked 30 or more cigarettes per day had more than 3.4 times higher risk than those who never smoked, while no increase in the risk was observed for those smoking less than 20 cigarettes per day and ex-smokers. Use of herb drugs, working under poor ventilation and nativity were also found to increase the NPC risk. In cases other than smoking 20 or more cigarettes per day and the frequent use of herb drugs, the synergistic interaction was not observed. In addition, male NPC individuals and Mainland Chinese were found to have relatively lower antibody titers as compared with female individuals or native Taiwanese.