Study design and participants

The Victorian Smoking and Health Survey is a cross-sectional telephone survey undertaken annually with a representative sample of adults aged 18 years and over, residing in the general population of the Australian state of Victoria. Fieldwork for the 2012 survey occurred between 1 November and 3 December inclusive.

Computer-assisted telephone interviews were conducted using a dual frame survey design incorporating samples generated by Random Digit Dialling (RDD) to landline and mobile phones. In 45% of cases where it was possible to match landline phone numbers to residential addresses, primary approach letters were posted prior to the phone call to give notice of a ‘community survey of health attitudes and behaviours’. As Australian mobile phone numbers have no geographic identifier, it was not possible to send approach letters to potential participants contacted through RDD to mobile phones. A helpline number was provided to all participants as a means of verifying the survey or obtaining further information.

After establishing contact with a verified landline sample number, up to nine call attempts were made to complete an interview. Calls to unanswered mobile phones were limited to four attempts. When calling a landline phone, interviewers asked to speak to the youngest male aged 18 years or over at home at the time of the call. If no men were available, the youngest adult woman in the household was selected to participate. Within the mobile RDD sample, the individual answering a call was considered to be the target for screening. A quota was applied to the landline sample to ensure that approximately 70% of interviews were conducted with metropolitan residents and 30% with rural residents, reflecting the population distribution of Victoria. Given the absence of geographic identifiers for the mobile numbers, no quota was applied to the mobile sample and state of residence was established on contact.

In total, 3126 landline and 878 mobile phone interviews were completed. Interviews were conducted in English only. Verbal consent was obtained from participants at the start of each interview. The overall response rate, defined as completed interviews as a proportion of the sample who could be contacted within the call cycle and who were identified as eligible for the survey, was 63%.

Ethics approval to undertake the survey was obtained from Cancer Council Victoria's Human Research Ethics Committee (HREC: 0018).

Measures

All questions were asked within the context of a broader 12 min population survey of attitudes and behaviours relating to smoking. Smokers were identified as individuals who currently smoked cigarettes, pipes and/or cigars daily, weekly or less than weekly. After being further asked about the types of tobacco currently consumed, current cigarette smokers were those who smoked factory-made cigarettes (FMC) or roll-your-own (RYO) cigarettes daily, weekly or less than weekly. All cigarette smokers were asked to specify their usual brand. Based on price class definitions listed in the grocery trade magazine Retail World,3 brands were classified into three segments (value, mainstream or premium). Where a brand was not listed, price per stick was used to determine the most appropriate classification, based on the thresholds used in Retail World. All RYO cigarette smokers (n=35) were assigned to the value market segment.

To ascertain exposure to the new plain packs, current cigarette smokers who reported smoking their usual FMC or RYO brand were asked: “Is the cigarette/tobacco pack you are currently smoking one of the new dark brown packs which has all of its logos removed and a large picture health warning on the front?”

To assess brand appeal, all current smokers were asked: “I'm going to read some statements about how you rate your current cigarettes compared to a year ago. I'd like you to tell me if you think that now, your cigarettes are higher, lower or about the same in terms of …’ a) ‘Quality?’ b)'Satisfaction?” To assess perceived harm, smokers were asked: “In the last week how often, if at all, did you think about the harm your smoking might be doing to you?” with response options being ‘never’, ‘rarely’, ‘sometimes’, ‘often’ and ‘very often’ (and aggregated for analysis into ‘often or very often’ vs all others) and: “Would you agree or disagree that the dangers of smoking have been exaggerated?” with response options from strongly agree, agree, neither, disagree and strongly disagree.

To examine quitting thoughts and intentions, smokers were asked: “Are you seriously considering quitting smoking in the next 6 months?”; “Are you planning to quit smoking in the next 30 days?” and “On a scale of 1 to 10, where 1 is lowest and 10 is highest, how would you rate quitting as a priority in your life?” Quitting salience was measured with the question: “During the past week, how often have you thought about quitting?” with responses ranging from ‘not at all’ to ‘several times a day’. Responses were aggregated for analysis into ‘once a day or more often’ versus ‘less often or not at all’.

Opinion about the new health warnings was determined by asking: “In order to strengthen the impact of the health messages on packs, the Federal government requires that from December 1 2012, the size of graphic health warnings will be increased to cover 75% of the front of the cigarette pack. Do you support or oppose increasing the size of graphic health warnings to 75% of the front of the cigarette pack?” The responses of smokers who ‘strongly’ or ‘somewhat’ supported the enlarged graphic health warnings were compared with the responses of those who opposed or had no opinion about the size increase. Plain packaging opinions were assessed by asking: “Tobacco companies often use cigarette packaging for promotional purposes. Because of this, the Federal government requires that from December 1 2012, cigarettes will be sold in plain packaging. This will mean that the packs will all look the same with the logos and colours removed. Just the brand in plain text and the graphic health warnings will remain on the packs. Do you approve or disapprove of this?” Respondents who reported that they approved or strongly approved were compared with others.

The average number of cigarettes smoked each day was calculated for daily and weekly smokers based on their self-reported consumption. For the purposes of analyses, less than weekly smokers were classified in the lowest consumption group (< 5 cigarettes/day). Smokers who had never attempted to quit were compared with smokers who had made at least one previous quit attempt, based on responses to the question: “Approximately how many times, if any, have you tried to give up smoking?”

During the fieldwork period, three antismoking advertisements were broadcast on television as part of a national antismoking mass media campaign. Respondents were read a short description of each advertisement and smokers who recalled seeing at least one were compared with those who did not recall any advertisements.

Respondents were classified into three socioeconomic status (SES) groups using the Index of Relative Disadvantage (IRSD),4 which ranks postal areas on a continuum of high-to-low disadvantage, taking into consideration characteristics including income, education, occupation and housing. The low SES (high disadvantage) group comprised people in the bottom 40% of ranked postal areas; the mid SES group included people who lived in areas with an IRSD score between 41% and 80% of ranked postal areas, while the high SES (lowest disadvantage) group lived in areas with an IRSD score between 81% and 100% of ranked postal areas.

Statistical analyses

All data were weighted by age and gender, based on the 2011 Australian census.5 Data weights also accounted for a participant's relative chance of inclusion in the landline or mobile phone sample frame, and their chance of selection based on the number of landlines in each household and number of in-scope people per household.

We first compared the characteristics of those smoking from plain and branded packs using bivariate logistic regression for binary variables and analysis of variance for continuous outcomes. Variables associated with plain or branded pack use at p<0.25 were included as covariates in multivariate logistic regression analyses, following Hosmer and Lemeshow,6 to examine whether current possession of a plain pack compared with a branded pack was associated with brand appeal, perceived harm, quitting thoughts and intentions, and support for packaging legislation and in analysis of covariance to determine if smoking from a plain pack was associated with higher ratings of quitting as a life priority.

A third set of models additionally controlled for the proportion of the sample interviewed during each survey week who reported smoking from a plain pack. We did this to control for the extent to which, as the survey period progressed, smokers would have been increasingly exposed to plain packs in their social networks, even though they may not have been personally smoking from one. Finally, in a sensitivity analysis, we repeated all analyses for brand loyal smokers, defined as those who had been smoking the same brand for a year.