Socioeconomic patterning of vaping by smoking status among UK adults and youth

BMC Public Health

Table 2 Research questions and the samples and variables analysed

	RQ1: Is vaping associated with SEP among youth and does this vary by smoking status?	RQ2: Is vaping associated with SEP among adults and does this vary by smoking status?	RQ3: Are socioeconomic inequalities in ex-smoking smaller for ever-smoking adults who vape than those who do not?
Sample	Youth aged 10–15	Adults aged 16+	Adults aged 16+
Exposure	SEP	SEP	SEP
Outcome	Vaping (overall and by smoking status)	Vaping (overall and by smoking status)	Ex-Smoking (among ever-smokers who do and do not vape)
Primary Confounders	Country Ethnicity Family Structure Interview Date	Gender Age Country Ethnicity Lives with Spouse/Partner Children in Household Interview Date	Gender Age Country Ethnicity Lives with Spouse/Partner Children in Household Interview Date
Intermediate Confounders	Gender^a Age^a Parental Smoking Parental Vaping	Current smoker at 1, 2 & 5 years previous	Current smoker at 1, 2 & 5 years previous

^aThese variables were probably not caused by SEP as indicated in Fig. 1, but for youth these are also unlikely to be common causes of SEP and vaping, so were included here, rather than as primary confounders