The effect of stimulants and their combined use with cigarettes on mortality: the case of betel quid.

Ten percent of the world's population use betel quid, making betel quid the fourth most used substance in the world. In Taiwan, there are an estimated 1.5 million users and the majority of them are also smokers. The number of people who died from oral cancer rose more than five times over the period from 1987 to 2006. In this study, we employ propensity score matching and the Weibull hazard model with instrumental variables to examine the health effects of betel quid chewing, in particular the health effect of its combined use with cigarettes. We show that betel quid chewing and smoking have a significant negative effect on health, and that the 10-year death hazard for joint users of betel quid and cigarettes doubles that for abstainers. Moreover, betel quid chewing is as harmful to health as smoking. We also find that betel quid chewing and smoking significantly increase the odds of dying from oral and oesophagus cancers.