Effect of restrictions on smoking at home, at school, and in public places on teenage smoking: cross sectional study

British Medical Journal, August 5, 2000 by Melanie A Wakefield, Frank J Chaloupka, Nancy J Kaufman, C Tracy Orleans, Dianne C Barker, Erin E Ruel

Abstract

Objective To determine the relation between extent of restrictions on smoking at home, at school, and in public places and smoking uptake and smoking prevalence among school students.

Design Cross sectional survey with merged records of extent of restrictions on smoking in public places.

Setting United States.

Participants 17 287 high school students.

Main outcome measures Five point scale of smoking uptake; 30 day smoking prevalence.

Results More restrictive arrangements on smoking at home were associated with a greater likelihood of being in an earlier stage of smoking uptake (P [is less than] 0.05) and a lower 30 day prevalence (odds ratio 0.79 (95% confidence interval 0.67 to 0.91), P [is less than] 0.001). These findings applied even when parents were smokers. More pervasive restrictions on smoking in public places were associated with a higher probability of being in a earlier stage of smoking uptake (P [is less than] 0.05) and lower 30 day prevalence (0.91 (0.83 to 0.99), P = 0.03). School smoking bans were related to a greater likelihood of being in an earlier stage of smoking uptake (0.89 (0.85 to 0.99), P [is less than] 0.05) and lower prevalence (0.86 (0.77 to 0.94), P [is less than] 0.001) only when the ban was strongly enforced, as measured by instances when teenagers perceived that most or all students obeyed the rule.

Conclusions These findings suggest that restrictions on smoking at home, more extensive bans on smoking in public places, and enforced bans on smoking at school may reduce teenage smoking.

Introduction

Restrictions on smoking at work and home are associated in adults with reduced daily smoking rate and increased cessation.[1-3] As these types of smoking restrictions become more pervasive,[1 4 5] smoking is likely to be perceived as more socially unacceptable and inconvenient. As yet, there has been little study of how smoking restrictions in public places might influence teenage use of tobacco.[6-9]

Banning smoking in the home, even when parents smoke, gives an unequivocal message to teenagers about the unacceptability of smoking, as do restrictions on smoking in public places. Exposure to environmental tobacco smoke during childhood has been suggested to increase tolerance for tobacco smoke and sensitise children to taking up active smoking in their teenage years by reducing the noxious deterrence of the first cigarette.[10] Thus, children who are exposed more often to parents smoking inside the home might have an increased likelihood of becoming established smokers.

Schools with smoking policies have significantly lower rates of student smoking,[11 12] but although school smoking bans are common, they are poorly complied with, so enforcement is highly important.[13] We sought to determine the relation between smoking restrictions in the home, at school, and in public places and measures of uptake of smoking and smoking prevalence by teenagers.

Participants and methods

The data used for this study were from a survey of United States school students in grades 9 to 12 (aged 14 to 17 years) administered in the spring of 1996. A three stage sampling procedure was used, with the primary sampling units being counties of the mainland United States. Within each selected primary sampling unit, one school was selected with probability proportional to enrolment in grades 9 through 12. Four reserve schools were drawn for each school in the primary sample; they were matched to selected schools by degree of urbanisation, type and size of school, percentage of children from ethnic minorities, and income level. When a selected school declined to participate, one of the matched reserve schools was asked to take part. At each selected school, one class was selected from each grade, and all students in these classes were eligible to participate in the survey. The figure shows that 73% of the schools selected as the primary or reserve sample participated in the survey and 80% of the students in sampled classes completed a survey questionnaire, yielding 17 287 questionnaires. Students were informed in writing that the survey was voluntary and that responses would remain confidential. The study design and questionnaire were approved by a Robert Wood Johnson Foundation advisory panel containing independent researchers with experience in conducting youth surveys about smoking.

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Questionnaire measures

Descriptors of the survey sample included sex; school grade (9-12); race (African American, Hispanic, white, other); whether adults living in the home were smokers (yes or no); and whether the respondent had siblings who smoked (yes or no). We classified respondents by stage of smoking uptake on the basis of specific responses to questions on smoking history and intentions to smoke in future that have been found to predict current smoking at follow up after three to four years.[4 14] "Non-susceptible non-smokers" had never smoked a cigarette, even a puff, and had a strong intention not to do so in future. "Susceptible non-smokers" had never smoked a whole cigarette but had weak intentions to stay non-smokers or they had previously had a puff but had strong intentions to stay non-smokers. "Early experimenters" had puffed on a cigarette more than 30 days before the survey but had weaker intentions not to smoke in future or had smoked a whole cigarette more than 30 days before the survey and had strong intentions not to smoke in future. "Advanced experimenters" had smoked a whole cigarette more than 30 days before the survey and had weak intentions not to smoke in future or had smoked in the past 30 days but had not smoked 100 cigarettes. Irrespective of their future intentions or recent smoking activity, respondents who indicated they had smoked 100 cigarettes in their lifetime were classified as "established smokers" Current smoking was defined by the traditional measure of having smoked in the past 30 days.