Uncovering the relation between betel quid chewing and cigarette smoking in Taiwan.

OBJECTIVE To describe the characteristics of betel quid chewers and to investigate the behavioural and mortality relations between betel quid chewing and cigarette smoking. METHOD Prevalence and mortality risks of betel quid chewers by smoking status were calculated, based on the National Health Interview Survey in 2001 and a community based cohort, respectively. Cox's proportional hazards model was used to adjust mortality risks for age, alcohol use, and education. RESULTS Almost all betel quid chewers were smokers, and most started chewing after smoking. Chewers were predominantly male, mostly in their 30s and 40s, more likely being among the lowest educational or income group, and residing in the eastern regions of Taiwan. On average, betel quid chewers who smoked consumed 18 pieces of betel quid a day, and smoked more cigarettes per day. Far more smokers use betel quid than non-smokers (27.5% v 2.5%), but ex-smokers quit betel quid more than smokers (15.1% v 6.8%). The significantly increased mortality of betel quid users who also smoked, for all causes, all cancer, oral cancer, and cancer of the nasopharynx, lung, and liver, was the result of the combined effects of chewing and smoking. Smokers who chewed betel quid nearly tripled their oral cancer risks from a relative risk of 2.1 to 5.9. Increasing the number of cigarettes smoked among betel quid chewers was associated with a synergistic effect, reflective of the significant interaction between the two. CONCLUSION To a large extent, the serious health consequences suffered by betel quid chewers were the result of the combined effects of smoking and chewing. Betel quid chewing should not be considered as an isolated issue, but should be viewed conjointly with cigarette smoking. Reducing cigarette smoking serves as an important first step in reducing betel quid chewing, and incorporating betel quid control into tobacco control may provide a new paradigm to attenuate the explosive increase in betel quid use in Taiwan.