Factors associated with waterpipe tobacco and cigarette smoking among current users in India, Russia, Egypt and Vietnam.

Note: AOR: adjusted odds ratios, CI: confidence interval; Current waterpipe/cigarettes: daily or weekly use.Russia education: 1) Completed secondary or less; 2) Completed higher than secondary; Russia occupation: omitted due to very low/no respondents in other categories.Female population were dropped when analysing dual waterpipe and cigarette smoking in Vietnam, as none of the female respondents were dual users of both products.