Etiological factors in nasopharyngeal carcinoma: a hospital-based, retrospective, case-control, questionnaire study.

A total of 379 Singapore Chinese patients with NPC were interviewed by use of a questionnaire covering the following items: occupation, level of education, language medium of education, personal and family history of nasal illnesses, types of medicines used, use of Chinese medicines for the nose and throat, use of soya sauce, Chinese tea, cooling drinks and alcohol, cigarette smoking (number and duration), cooking fuels and use of incense (frequency and duration) and of anti-mosquito coils. The same questionnaire was given to two groups of controls: 595 patients with diseases of the ear, nose and throat other than NPC and 1 044 patients with diseases other than cancer or otorhinolaryngeal disease. NPC patients differed significantly from both groups of controls in that they showed stronger associations with personal history of nasal illnesses, family history of nasal illnesses, use of Chinese medicines for the nose and throat and exposure to smoke from anti-mosquito coils.