An RCT of a Smartphone-based TID Programme

Experimenteel: TID

Messages will be sent 1-2 times per week containing information that aims to denormalise the tobacco industry.

Ander: Smartphone-based messages

For the TID arm, the messages' contents include the tobacco industry's (TI's) anti-smoking campaigns that made smoking more grown-up and more appealing to youth; the TI's role in smoking in movies; etc.

For the sugar sweetened beverage (SSB) arm, the messages' contents include the disease conditions linked to SSBs, and the interference of sugar industry in scientific research.

Ander: Sugar sweetened beverages

Messages will be sent 1-2 times per week containing information on the adverse health effects of sugar sweetened beverages.

Ander: Smartphone-based messages

For the TID arm, the messages' contents include the tobacco industry's (TI's) anti-smoking campaigns that made smoking more grown-up and more appealing to youth; the TI's role in smoking in movies; etc.

For the sugar sweetened beverage (SSB) arm, the messages' contents include the disease conditions linked to SSBs, and the interference of sugar industry in scientific research.

TID beliefs in parents

Parents will report their opinions towards 4 sentences: 1) Tobacco companies are a respectable industry; 2) the tobacco industry does everything it can to get young people to smoke; 2) the tobacco industry use many tactics to resist tobacco control regulations; 4) the tobacco industry deceived the public for financial interests. All the 4 questions have 5 options from definitely yes to definitely no. The options will be recoded into 0-4 or 4-0, as appropriate, with higher scores indicating more negative attitudes towards the industry. A sum of scores from the 4 questions will be deemed a measurement of TID beliefs.

TID beliefs in children

Students will report their opinions towards 4 sentences: 1) Tobacco companies are a respectable industry; 2) the tobacco industry does everything it can to get young people to smoke; 2) the tobacco industry use many tactics to resist tobacco control regulations; 4) the tobacco industry deceived the public for financial interests. All the 4 questions have 5 options from definitely yes to definitely no. The options will be recoded into 0-4 or 4-0, as appropriate, with higher scores indicating more negative attitudes towards the industry. A sum of scores from the 4 questions will be deemed a measurement of TID beliefs.

Tobacco related communication reported by parents

Parents will report whether they said the following to children in the past 30 days: 1) harm of smoking 2) harm of secondhand smoking 3) criticise smoking behaviour 4) approve tobacco control measures. Each of the messages will be analyse as a binary outcome.

Sugar sweetened beverage (SSB) related communication reported by parents

Parents will report whether they said the following to children in the past 30 days: 1) harm of SSB 2) certain kind of drinks contain sugar 3) don't drink or drink less SSB. Each of the messages will be analyse as a binary outcome.

Tobacco related communication reported by children

Students will report whether they heard the following from parents in the past 30 days: 1) harm of smoking 2) harm of secondhand smoking 3) criticize smoking behaviour 4) approve tobacco control measures. Each of the messages will be analyse as a binary outcome.

SSB related communication reported by children

Students will report whether they heard the following from parents in the past 30 days: 1) harm of SSB 2) certain kind of drinks contain sugar 3) don't drink or drink less SSB. Each of the messages will be analyse as a binary outcome.

Intention to smoke in children

Two questions will be used to assess this outcome: 1) do you think you will smoke in the next 12 months? 2) If one of your good friends offers you a cigarette, will you smoke it? Response options are definitely not/probably not/probably yes/definitely yes. Those choosing options other than "definitely not" for either of the questions will be deemed having intention to smoke; the other students will be deemed having no intention to smoke.

Home exposure to secondhand smoke in children reported by children

One question will be asked: 1) On how many of the past 7 days did someone smoke near you at home? (Options 0 day/1/2/3/4/5/6/7). The responses will dichotomised into a binary indicator of secondhand smoke exposure (no/any) and analysed as an outcome.

Home exposure to secondhand smoke in children reported by parents

One question will be asked: 1) On how many of the past 7 days did someone smoke near your children at home? (Options 0 day/1/2/3/4/5/6/7). The responses will dichotomised into a binary indicator of secondhand smoke exposure (no/any) and analysed as an outcome.

Parents' support for tobacco control

Parents will report their opinions towards 4 sentences: 1) government should adopt plain packaging; 2) government should impose stronger regulation on tobacco; 3) government should strengthen the prevention of the harm of tobacco. The options were strongly support/support/neutral/oppose/strongly oppose. The options will be recoded into 4-0, with higher scores indicating stronger support for tobacco control. A sum of scores from the 4 questions will be deemed a measurement of parents' support for tobacco control.

Negative attitude towards smoking in parents

Parents will be asked "your attitude towards smoking is" with options of very positive/positive/neutral/negative/very negative. The options will be dichotomised as very negative vs others (negative/neutral/positive/very positive) for analysis.

Negative attitude towards smoking in children

Children will be asked "your attitude towards smoking is" with options of very positive/positive/neutral/negative/very negative. The options will be dichotomised as very negative vs others (negative/neutral/positive/very positive) for analysis.

Past 7-day consumption of SSB and water in children reported by children

Children will be asked "On how many of the past 7 days did you drink SSBs?" and "On how many of the past 7 days did you drink water?" For both questions, the options were 0/1/2/3/4/5/6/7 days. These two variables will be analysed as both binary (No (0 day) vs any (1/2/3/4/5/6/7 days)) and continuous variables.

Past 7-day consumption of SSB and water in children reported by parents

Parents will be asked "On how many of the past 7 days did you drink SSBs?" and "On how many of the past 7 days did you drink water?" For both questions, the options were 0/1/2/3/4/5/6/7 days. These two variables will be analysed as both binary (No (0 day) vs any (1/2/3/4/5/6/7 days)) and continuous variables.