Substance Use & Misuse, 50:387–393, 2015 C 2015 Informa Healthcare USA, Inc. Copyright ISSN: 1082-6084 print / 1532-2491 online DOI: 10.3109/10826084.2014.984848
ORIGINAL ARTICLE
The Relationship Between Secondhand Smoke Exposure, Pro-Tobacco Social Influences, and Smoking Susceptibility Among Nonsmoking Zambian Adolescents Israel Terungwa Agaku1 , Tino Maliselo2 and Olalekan A. Ayo-Yusuf2,3 1
Center for Global Tobacco Control, Harvard School of Public Health, Boston, Massachusetts, USA; 2 School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa; 3 Sefako Makgatho Health Sciences University, Medunsa, Pretoria ing laws (World Health Organization, 2003, 2013). For example, even though a national smoke-free law exists prohibiting smoking in public places—including healthcare facilities, public transit, universities, and government facilities—compliance is generally only moderate although some success has been reported recently in the capital city (Lusaka) regarding enforcement of the smokefree law (Drope 2010; World Health Organization, 2013). Protecting nonsmokers from secondhand smoke (SHS) is a public health priority because SHS is a potent health hazard that has been causally linked to a plethora of disease conditions, including lung cancer and stroke among adults, as well as middle ear disease and sudden infant death syndrome among children (US Department of Health and Human Services, 2006, 2014). Children and adolescents are particularly susceptible to SHS exposure because of their having less control over environments where smoking may be occurring such as in the family car or at home, and also being less likely to be aware of the dangers of SHS exposure compared to adults. Adolescents may be susceptible to being exposed to SHS from several sources, including at school, in private cars, and at home, especially in the absence of smokefree rules (Cartmell et al., 2011; King, Dube, & Tynan, 2012; Olufajo & Agaku, 2014). The degree of overall SHS exposure among nonsmoking adolescents could reflect underlying exposure to different behavioral, environmental, and social pro-tobacco influences, such as living with a smoker or having smoking friends—factors which have been shown to predict smoking among youths (US Department of Health and Human Services, 2012). Hence, we hypothesized that the frequency or extent of self-reported SHS exposure among adolescents would be associated with their overall exposure to pro-tobacco social influences and, in turn, with their susceptibility to
Background: We tested the hypothesis that the extent of secondhand smoke (SHS) exposure among nonsmoking adolescents would be associated with their overall exposure to pro-tobacco social influences. Methods: Data were analyzed using descriptive and multivariate methods from the 2011 Zambia Global Youth Tobacco Survey. Results: The odds of SHS exposure increased with increasing exposure to pro-tobacco advertisements. About 39.5% of the gap in SHS exposure between nonsmokers with low versus high smoking susceptibility was attributable to differences in parental or peer smoking. Conclusions: Sustained efforts are needed to denormalize tobacco use in order to reduce youth susceptibility to tobacco use. Keywords secondhand smoke, adolescents, cigarettes, tobacco, smoking, susceptibility
INTRODUCTION
Zambia—a lower middle-income country in the World Health Organization (WHO) African region with a population of approximately 13 million people—is fast becoming a major tobacco leaf producer in the region (Central Statistical Office, Republic of Zambia, 2011; Drope, 2010; World Bank, 2011). Tobacco use is a significant public health problem in the country; the prevalence of daily cigarette smoking among adults was 11% during 2011, while the prevalence of current cigarette smoking among adolescents aged 13–15 years was 6.2% during the same year (World Health Organization, 2011, 2013). Although Zambia became a party to the WHO Framework Convention on Tobacco Control on May 23, 2008, the tobacco control legislative environment is still relatively weak, with little enforcement of exist-
Address correspondence to Dr Israel Terungwa Agaku, Harvard School of Public Health, Center for Global Tobacco Control, 677 Huntington Avenue, Boston, MA 02125, USA. Email: [email protected]
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smoking. To test this hypothesis, we analyzed data from the Global Youth Tobacco Survey (GYTS) for Zambia during 2011 to measure the relationship between SHS exposure, pro-tobacco social influences, and smoking susceptibility among Zambian adolescents. METHODS Data Source
Data were obtained from the 2011 National Zambia GYTS. A two-stage cluster sample design was used to produce representative data for the country. At the first stage, schools were selected with probability proportional to enrollment size. At the second stage, classes were randomly selected and all students in selected classes were eligible to participate. A total of 3,377 male and female students in grades 7, 8, and 9 (ages ranging from 11 to 16 years or older) completed the self-administered questionnaires in classrooms, yielding an overall response rate of 55.7%. Measures
Secondhand Smoke Exposure Secondhand smoke exposure was assessed with the following three questions: “During the past 7 days, on how many days have people smoked in your home or in your presence?”; “During the past 7 days, on how many days have people smoked in your presence, in enclosed public places?”; and “During the past 7 days, on how many days have people smoked in your presence, in outdoor public places?” For all the three questions, categorical response options were: “0” days; “1 to 2” days; “3 to 4” days; “5 to 6” days; or “7” days. Any response other than “0” days was categorized as being exposed to SHS in the respective environment assessed. For our analyses, we categorized respondents as having any SHS exposure if they reported being exposed to SHS from at least one of the three environments assessed (i.e., home; enclosed public places; or outdoor public places). Respondents with missing observations for any of the three environments (4.0%) were excluded from the analyses. Cigarette Smoking Status and Smoking Susceptibility Ever cigarette smokers were students who reported that they had experimented with cigarette smoking, even one or two puffs during their lifetime. Those who had never experimented with cigarette smoking were categorized as never smokers. Current cigarette smokers were students who reported smoking cigarettes on at least one day within the past 30 days. Former cigarette smokers were students who reported ever smoking cigarettes during their lifetime but did not report smoking a cigarette within the past 30 days. Both never and former smokers were categorized as current nonsmokers. Respondents were asked two questions to assess their smoking intentions: “At any time during the next 12 months, do you think you will smoke a cigarette?” and “If one of your best friends offered you a cigarette, would you smoke it?” Categorical response options to both questions were: “definitely not,” “probably not,” “probably yes,” or “definitely yes.” Nonsmokers were classified as
being highly susceptible to cigarette smoking if they responded in any way other than “definitely not” to either question. On the other hand, nonsmokers who expressed a firm conviction not to smoke cigarettes (i.e., a response of “definitely not” to both questions) were categorized as having low susceptibility to cigarette smoking. Perception about the social acceptability of cigarette smoking was assessed with the following question: “Does smoking cigarettes help people feel more or less comfortable at celebrations, parties, or in social gatherings?” Categorical responses included the following: “More comfortable,” “less comfortable,” or “no difference from nonsmokers.” Pro-tobacco Social Influences In line with the socio-ecological model (McLeroy, Bibeau, Steckler, & Glanz, 1988), we measured several levels of pro-tobacco social influences, including proximal or inter-personal factors, as well as more distal or environmental factors. Proximal pro-tobacco influences assessed included parental and peer smoking, both categorized as having at least one parent or close friend that smoked cigarettes, versus none that smoked. Environmental pro-tobacco influences assessed included exposure to tobacco advertisements from six different media, namely: movies; television programs; retail stores; billboards; newspapers/magazines; and outdoor community events such as fairs, concerts, or sporting events. Within the survey, respondents could select one of the three response options that best described their frequency of exposure to each of the six media assessed. The response options were: (1) “a lot,” (2) “sometimes”/“a few,” or (3) “none”/“never.” Within our analyses, students were categorized as being exposed to a particular advertisement medium if they selected a response option of “sometimes”/“a few,” or “a lot.” On the other hand, students were categorized as being unexposed if they selected a response option of “none”/“never,” or if they reported that they did not use or access the medium of interest at all. Receptivity to pro-tobacco advertisements was defined as a “Yes” response to the following question: “Do you have something (t-shirt, pen, backpack, etc.) with a cigarette brand logo on it?” Statistical Analyses
Data were summarized using descriptive statistics (percentage values) and further analyzed using multivariate logistic regression. Prevalence estimates with relative standard errors of ≥35% were considered statistically unreliable. Comparison of prevalence estimates was performed with the chi-squared statistic (p < .05). The total number of distinct sources of pro-tobacco advertisements that respondents reported being exposed to was added for each student (range: 0 to 6) and included as a variable in the multivariate analyses to assess for a dose-response relationship between environmental pro-tobacco social influences and SHS exposure. In a separate model, a composite variable denoting the total number of distinct environments where respondents were exposed to SHS within the past 7 days (i.e., 0, 1, or ≥2 environments based on
SECONDHAND SMOKE AND PRO-TOBACCO SOCIAL INFLUENCES
exposures from home; enclosed public places; or outdoor public places) was included as an independent variable to assess the relationship with smoking susceptibility among nonsmokers. All multivariate analyses controlled for age, sex, and ever smoking status. Differences in SHS exposure by smoking susceptibility status among nonsmokers were further explored using the Blinder–Oaxaca decomposition analysis. All analyses were weighted and performed with Stata version 11 (Stata Corp. 2009, College Station, TX). RESULTS
In total, 50.8% of study participants were girls and age distribution among all respondents was as follows: 11–13 years (25.8%); 14–15 years (42.8%); and ≥16 years (31.5%). Overall smoking prevalence was 7.0%, while prevalence of smoking susceptibility among nonsmokers was 26.7%. Prevalence of SHS Exposure
Approximately 59.5% of all students were exposed to SHS from at least one source. By specific sources of SHS exposure, 33.1% were exposed at home, 42.6% were exposed in enclosed public places, while 45.0% were exposed in outdoor public places. By cigarette smoking status, SHS exposure prevalence was as follows: current cigarette smokers (87.9%), former cigarette smokers (69.6%), never cigarette smokers with high smoking susceptibility (56.3%), and never cigarette smokers with low smoking susceptibility (51.2%). SHS exposure prevalence increased with increasing age, and was lowest among students aged 11–13 years (55.4%) and highest among students aged ≥16 years (61.4%) (Table 1). Students who perceived that smoking made one more comfortable at social events had higher prevalence of any SHS exposure (63.4%) compared with those who believed that smoking made one less comfortable at social events (58.7%) (p < .05). Students who had at least one parent that smoked had a significantly higher prevalence of any SHS exposure (76.5%) compared with those that had no smoking parent (54.8%). Similarly, students with one or more close friends that smoked had a significantly higher prevalence of any SHS exposure (71.6%) compared with those with no close friend that smoked (52.8%). The prevalence of any SHS exposure increased with the number of different pro-tobacco advertisements that students were exposed to, from 30.9% among students who reported not being exposed to any source of pro-tobacco advertisement to 70.1% among students who reported being exposed to all six sources of pro-tobacco advertisements (p < .05). Students who owned a tobacco-branded item had a significantly higher prevalence of any SHS exposure (69.5%) compared with those with no tobacco-branded item (56.0%). Relationship Between SHS Exposure and Exposure to Pro-Tobacco Social Influences
Within adjusted analyses, nonsmokers with high smoking susceptibility had higher odds of any SHS exposure
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compared with those with low smoking susceptibility (adjusted odds ratio [aOR] = 1.26; 95% confidence interval [CI]: 1.04–1.53). Nonsmokers who had one or both parents as smokers (aOR = 2.02; 95% CI: 1.59–2.57), or one or more close friends as smokers (aOR = 1.68; 95% CI: 1.39–2.03), had higher odds of being exposed to SHS compared with those that had no smoking parents or close friends respectively. As shown in Table 2, a dose-response gradient was observed in the adjusted relationship between exposure to pro-tobacco advertisements, and the odds of exposure to any SHS among nonsmokers. Compared with nonsmokers who were not exposed to any pro-tobacco advertisements, increased odds of any SHS exposure were observed among nonsmokers who were exposed to one (aOR = 1.32), two (aOR = 2.47), three (aOR = 3.27), four (aOR = 4.12), five (aOR = 5.37), or all six sources of protobacco advertisements (aOR = 5.76) (all p-values < .05). Similarly, nonsmokers that owned a tobacco-branded item had higher odds of being exposed to any SHS compared with those with none (aOR = 1.39; 95% CI: 1.10–1.76). Nonsmokers who were exposed to SHS from ≥2 distinct environments had higher odds of being highly susceptible to cigarette smoking compared with those not exposed to SHS from any environment (aOR = 1.43; 95% CI: 1.16–1.77). Similarly, nonsmokers who reported being daily exposed to SHS in home (aOR = 1.57; 95% CI: 1.10–2.25) or at enclosed public areas (aOR = 1.68; 95% CI: 1.22–2.32) had higher odds of being highly susceptible to cigarette smoking compared with those not exposed to SHS on any day in the respective environments (Table 3). In total, 39.5% (95% CI: 25.6–53.5) of the explainable gap in SHS exposure between nonsmokers with low versus high smoking susceptibility was attributable to higher proportions of parental or peer smoking among highly susceptible nonsmokers. Differences in exposure to protobacco advertisements between nonsmokers with low versus high smoking susceptibility (with higher exposure noted among highly susceptible nonsmokers) further accounted for 9.0% (95% CI: 4.0–14.0) of the explainable differences in any SHS exposure In contrast, differences in socio-demographic characteristics, such as age and sex, accounted for only 1.3% (95% CI: 0.1–3.0) of the explainable differences in SHS exposure by smoking susceptibility status among nonsmokers. DISCUSSION
We found a significant association between increasing levels of exposure to pro-tobacco social influences and increased odds of SHS exposure among nonsmokers. Nonsmokers who were exposed to SHS from multiple environments, as well as those who were exposed to SHS on a daily basis at home or in enclosed public places, all had higher odds of being susceptible to cigarette smoking when compared with those unexposed to SHS. While the relationship between SHS exposure and smoking susceptibility among nonsmokers may be partly explained by increased sensitivity to nicotine following continuous
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TABLE 1. Prevalence of any secondhand smoke exposure by smoking status and other selected characteristics, GYTS, Zambia, 2011
Characteristics Total Age (years) 11–13 14–15 ≥16 Sex Boy Girl Perceived social acceptability of smoking at social events Smoking makes one more comfortable Smoking makes one less comfortable No difference between smokers and nonsmokers Parental smoking None smokes One or both smoke Peer smoking None smokes One or all smoke Total number of distinct sources of pro-tobacco advertisement exposures reporteda None One Two Three Four Five Six Receptivity to tobacco advertisements (owning a tobacco-branded item) None One or more
Never cigarette Never cigarette smokers with low smokers with high smoking smoking susceptibility, susceptibility, n = n = 533 % (95% CI) 1,604 % (95% CI)
Overall N = 3,315 % (95% CI)
Current cigarette smokers n = 186 % (95% CI)
Former cigarette smokers n = 331 % (95% CI)
59.5 (57.8–61.2)
87.9 (83.0–92.7)
69.6 (64.5–74.6)
56.3 (52.0–60.6)
51.2 (48.7–53.6)
55.4 (52.0–58.8) 60.6 (58.1–63.2) 61.4 (58.4–64.4)
88.9 (77.0–100.0) 86.3 (78.4–94.2) 90.0 (83.0–97.0)
71.6 (61.3–81.9) 68.6 (60.8–76.4) 70.9 (62.1–79.7)
57.6 (48.7–66.5) 53.2 (46.6–59.9) 58.9 (51.6–66.2)
44.5 (39.9–49.2) 55.8 (52.1–59.5) 50.7 (45.9–55.5)
60.2 (57.7–62.6) 58.3 (55.9–60.7)
85.9 (78.7–93.0) 90.4 (83.7–97.2)
69.3 (62.2–76.4) 69.2 (61.7–76.7)
54.7 (48.6–60.7) 57.3 (51.1–63.4)
51.4 (47.8–55.0) 50.6 (47.2–54.0)
63.4 (60.4–66.3)
93.1 (86.6–99.6)
71.8 (63.2–80.5)
60.1 (52.7–67.5)
53.9 (49.3–58.4)
58.7 (56.1–61.3)
89.6 (82.2–96.9)
68.8 (60.7–76.9)
61.3 (54.8–67.9)
50.8 (47.2–54.4)
55.8 (52.2–59.3)
79.5 (67.6–91.5)
68.3 (58.2–78.4)
43.0 (34.2–51.8)
49.5 (43.9–55.1)
54.8 (52.9–56.8) 76.5 (73.4–79.7)
83.3 (75.6–91.0) 94.9 (90.0–99.8)
66.4 (60.2–72.5) 79.1 (70.5–87.7)
52.4 (47.5–57.3) 71.2 (62.7–79.6)
49.6 (47.0–52.2) 64.8 (57.8–71.8)
52.8 (50.7–55.0) 71.6 (69.0–74.2)
83.7 (73.3–94.0) 89.3 (83.9–94.8)
64.0 (56.8–71.1) 76.1 (69.0–83.1)
50.3 (44.9–55.8) 66.8 (60.0–73.7)
49.4 (46.6–52.2) 59.8 (54.5–65.1)
30.9 (23.6–38.3) 38.5 (32.7–44.3) 54.0 (49.5–58.6) 60.1 (56.2–64.1) 65.9 (62.0–69.7) 69.5 (65.4–73.6) 70.1 (64.9–75.4)
. . .b 83.3 (62.2–100.0) 76.5 (56.3–96.6) 83.3 (70.0–96.7) 92.1 (83.5–100.0) 88.0 (75.3–100.0) 95.2 (86.1–100.0)
. . .b 52.9 (29.2–76.7) 62.8 (48.3–77.2) 67.2 (55.4–79.0) 75.0 (63.7–86.3) 69.1 (56.9–81.3) 80.0 (67.6–92.4)
27.3 (8.7–45.9) 40.0 (26.4–53.6) 53.1 (40.9–65.4) 60.0 (50.4–69.6) 57.7 (47.9–67.6) 66.7 (56.4–76.9) 72.1 (58.7–85.5)
28.4 (19.3–37.5) 29.1 (22.0–36.2) 45.8 (39.3–52.3) 49.4 (43.4–55.5) 58.6 (52.7–64.6) 66.1 (60.3–72.0) 65.6 (58.0–73.1)
56.0 (54.0–58.0) 69.5 (65.8–73.1)
85.1 (77.9–92.3) 89.8 (82.1–97.5)
64.8 (58.4–71.2) 79.0 (70.1–87.9)
54.3 (49.3–59.3) 63.5 (53.9–73.2)
50.8 (48.2–53.5) 53.4 (46.0–60.7)
Notes. Any secondhand smoke exposure was defined as a report by a student that they were exposed to tobacco smoke at any of the following places: home, enclosed public areas, or outdoor public areas. GYTS = Global Youth Tobacco Survey; CI = confidence interval. a Total number of pro-tobacco advertisements was calculated by counting the total number of pro-tobacco advertisements reported by respondents from the six different sources assessed in the survey. These sources included: movies, television programs, retail stores, billboards, newspapers/magazines, and outdoor community events such as fairs or sporting events. b Statistically unreliable estimates, with relative standard errors ≥35%.
and prolonged exposure to SHS (Wilson-Frederick et al., 2011), the extent of SHS exposure may largely be a proxy for the extent of exposure to powerful pro-tobacco social influences which may mold adolescent nonsmokers’ perception of smoking as normative. This is supported by the fact that the majority of the explainable differences in SHS exposure by smoking susceptibility status in our study was accounted for by parental and peer smoking. These findings may have some implications for tobacco screening and counseling among youths in order to target those at high risk for smoking initiation. Thus, in addition
to asking adolescents if they currently use tobacco, asking them about their frequency of SHS exposure within the past week, or the different environments in which they were exposed to SHS may potentially help to identify nonsmokers who may be susceptible to cigarette smoking. The role of parental and peer smoking on smoking susceptibility and initiation has been well documented in the scientific literature (Kelly et al., 2010; Mak, Ho, & Day, 2012; US Department of Health and Human Services, 2012). Parent’s smoking habit may influence adolescents’ attitude toward smoking as an acceptable norm
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TABLE 2. Crude and adjusted relationship between pro-tobacco social influences and any secondhand smoke exposure among current nonsmokers, GYTS, Zambia, 2011 Characteristic Smoking susceptibility Low High Perceived social acceptability of smoking at social events Smoking makes one more comfortable Smoking makes one less comfortable No difference between smokers and nonsmokers Parental smoking None smokes One or both smoke Peer smoking None smokes One or all smoke Total number of distinct sources of pro-tobacco advertisement exposures reporteda None One Two Three Four Five Six Receptivity to tobacco advertisements (owning a tobacco-branded item) None One or more
Crude effect on secondhand smoke exposure, cOR (95% CI)
Adjusted effect on secondhand smoke exposure, aOR (95% CI)
1.00 (referent) 1.34 (1.11–1.62)
1.00 (referent) 1.26(1.04–1.53)∗
1.00 (referent) 0.89 (0.74–1.08) 0.75 (0.60–0.94)
1.00 (referent) 0.89 (0.74–1.08) 0.74 (0.58–0.91)∗
1.00 (referent) 2.13 (1.69–2.69)
1.00 (referent) 2.02 (1.59–2.57)∗
1.00 (referent) 1.81 (1.51–2.18)
1.00 (referent) 1.68 (1.39–2.03)∗
1.00 (referent) 1.29 (0.80–2.09) 2.53 (1.62–3.94) 3.08 (2.00–4.75) 3.99 (2.58–6.18) 5.22 (3.35–8.13) 5.78 (3.58–9.32)
1.00 (referent) 1.32 (0.81–2.15) 2.47 (1.57–3.89)∗ 3.27 (2.09–5.10)∗ 4.12 (2.63–6.45)∗ 5.37 (3.41–8.45)∗ 5.76 (3.53–9.40)∗
1.00 (referent) 1.45 (1.15–1.82)
1.00 (referent) 1.39 (1.10–1.76)∗
Notes. Any secondhand smoke exposure was defined as a report by a student that they were exposed to tobacco smoke at any of the following places: home, enclosed public areas, or outdoor public areas. GYTS = Global Youth Tobacco Survey; cOR = crude odds ratio; aOR = adjusted odds ratio; CI = confidence interval. a Total number of pro-tobacco advertisements was calculated by counting the total number of pro-tobacco advertisements reported by respondents from the six different sources assessed in the survey. These sources included: movies, television programs, retail stores, billboards, newspapers/magazines, and outdoor community events such as fairs or sporting events. ∗ Statistically significant adjusted odds ratios. Multivariate analyses adjusted for age, sex, and ever smoking status.
(Mak et al., 2012; Nebot et al., 2004; O’Loughlin et al., 2009). Parents who smoke may also be less restrictive on their own children picking up smoking habits (Brown et al., 2010). More so, children of parents who smoke may have easier access to cigarettes at home and learn smoking behavior by imitating their parents in line with the social learning theory. Similarly, having friends who are smokers may increase smoking susceptibility among adolescents because of peer pressure to conform or for the feeling
of acceptance (Brown et al., 2010). In addition, hanging around with friends who smoke or being present at social events where smoking is occurring may serve as cues that may prompt smoking relapse among former smokers (Salgado-Garcia, Cooper, & Taylor, 2013). These findings underscore the need for stronger measures to denormalize tobacco use and reduce adolescent exposure to pro-tobacco social influences, including tobacco advertising and promotion. According to the WHO
TABLE 3. Relationship between smoking susceptibility and the number of days of secondhand smoke exposure among current nonsmokers in different environments, GYTS, Zambia, 2011 Adjusted effect on Smoking susceptibility Number of days of secondhand smoke exposure within past 7 days
Exposure source: home aOR (95% CI)
Exposure source: enclosed public areas aOR (95% CI)
Exposure source: outdoor public areas aOR (95% CI)
0 days 1 to 2 days 3 to 4 days 5 to 6 days 7 days
1.00 (referent) 1.25 (0.93–1.69) 0.92 (0.58–1.45) 1.27 (0.76–2.11) 1.57 (1.10–2.25)∗
1.00 (referent) 1.24 (0.96–1.59) 1.33 (0.90–1.96) 1.42 (0.92–2.21) 1.68 (1.22–2.32)∗
1.00 (referent) 0.86 (0.66–1.12) 1.20 (0.84–1.73) 1.53 (1.01–2.33)∗ 1.35 (1.00–1.83)
Notes. GYTS = Global Youth Tobacco Survey; aOR = adjusted odds ratio; CI = confidence interval. ∗ Statistically significant adjusted odds ratios. Multivariate analyses adjusted for age, sex, and ever smoking status.
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report (2013) on the global tobacco epidemic, no national bans currently exist in Zambia on tobacco advertising on national/international television, radio, newspapers/magazines, points-of-sale, billboards, or other forms of outdoor advertising. Previous studies have shown a significant relationship between increased exposure to pro-tobacco advertisements and increased susceptibility, as well as actual experimentation with tobacco products (Agaku & Ayo-Yusuf, 2013; Dube, Arrazola, Lee, Engstrom, & Malarcher, 2013). Adolescents in particular are more receptive to tobacco promotional activities than adults, thus emphasizing the need for stronger restrictions in youth-targeted tobacco advertisements (Andrews, Netemeyer, Burton, Moberg, & Christiansen, 2004; US Department of Health and Human Services, 2012). The findings in this study are subject to some limitations. First, SHS exposure was self-reported and may have been subject to misreporting. However, recall was limited to the past 7 days, a relatively short period. Second, other determinants of increased smoking susceptibility and SHS exposure were not assessed due to lack of data, including sibling and teacher smoking. Third, the cross-sectional nature of the data precludes any causal inferences and only associations can be deduced. Finally, the study may be limited in generalizability to other countries with stronger comprehensive tobacco control programs, especially with regard to SHS exposure in public areas.
THE AUTHORS Dr. Israel Terungwa Agaku, conducts epidemiologic research on tobacco products with a focus on the contribution to dependence and abuse liability, particularly among adolescents and young adults.
Dr Tino is a public health practitioner working with the Zambian Ministry of Health and his research interest is in tobacco control advocacy.
Professor Olalekan A Ayo-Yusuf is a Dean at the University of Limpopo and his research interest is in studying alternative tobacco use and tobacco control policy.
CONCLUSIONS
This study demonstrated that SHS exposure among Zambian adolescents was associated with smoking susceptibility and exposure to pro-tobacco social influences. These findings highlight the need for multilevel approaches in adolescent tobacco use prevention interventions. In particular, the results underscore the need for stronger restrictions on tobacco advertising that targets youths. Stronger enforcement of smoke-free bans may also help protect nonsmoking youths and adults from involuntary exposure to SHS and help to denormalize tobacco use.
Declaration of Interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article. Dr. Israel Agaku initiated the reported research while affiliated with the Center for Global Tobacco Control at Harvard University. He is currently affiliated with the Centers for Disease Control and Prevention’s Office on Smoking and Health. The research in this report was completed and submitted outside of the official duties of his current position and does not reflect the official policies or positions of the Centers for Disease Control and Prevention.
GLOSSARY
Pro-tobacco social influences: Social factors that may catalyze smoking initiation or progression. As used in this study, this encompasses both proximal influences (e.g., parental and peer smoking) and environmental influences (e.g., exposure to pro-tobacco advertising). Secondhand smoke: Tobacco smoke exhaled from someone smoking or produced by a smoldering cigarette and involuntarily inhaled by a nonsmoker. Smoking susceptibility: A lack of a firm conviction not to smoke a cigarette in the future, or if offered by a close friend.
REFERENCES Agaku, I. T., & Ayo-Yusuf, O. A. (2013). The effect of exposure to pro-tobacco advertising on experimentation with emerging tobacco products among US adolescents. Health Education and Behavior, 41(3), 275–280.
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Andrews, J. C., Netemeyer, R. G., Burton, S., Moberg, D. B., & Christiansen, A. (2004). Understanding adolescent intentions to smoke: An examination of relationships among social influence, prior trial behavior, and antitobacco campaign advertising. Journal of Marketing, 68, 110–123. Brown, A. K., Moodie, C., Hastings, G., Mackintosh, A. M., Hassan, L., & Thrasher, J. (2010). The association of normative perceptions with adolescent smoking intentions. Journal of Adolescence, 33(5), 603–614. doi:10.1016/j.adolescence.2009.12.003; 10.1016/j.adolescence.2009.12.003 Cartmell, K. B., Miner, C., Carpenter, M. J., Vitoc, C. S., Biggers, S., Onicescu, G., . . . Alberg, A. J. (2011). Second-hand smoke exposure in young people and parental rules against smoking at home and in the car. Public Health Reports (Washington, DC 1974), 126(4), 575–582. Central Statistical Office (CSO), Central Board of Health (CBoH), ORC Macro. Zambia Demographic and Health Survey 2001/2002. CSO, CBoH and ORC Macro, Lusaka, Zambia and Calverton, Maryland; 2003 Central Statistical Office (CSO), Ministry of Health (MOH), Tropical Diseases Research Centre (TDRC), University of Zambia, and Macro International Inc. Zambia Demographic and Health Survey 2007. CSO and Macro International, Calverton, Maryland; 2009. Central Statistical Office, Republic of Zambia. (2011). Census of population and housing report. Lusaka, Zambia: Central Statistical Office (CSO), Republic of Zambia. Drope, J. (2010). Tobacco control in Africa (pp. 261–282). London: Anthem Press Dube, S. R., Arrazola, R. A., Lee, J., Engstrom, M., & Malarcher, A. (2013). Pro-tobacco influences and susceptibility to smoking cigarettes among middle and high school students—United States, 2011. Journal of Adolescent Health, 52(5 Suppl), S45–S51. doi:10.1016/j.jadohealth.2012.07.007 Kelly, A. B., O’Flaherty, M., Connor, J. P., Homel, R., Toumbourou, J. W., Patton, G. C., & Williams, J. (2010). The influence of parents, siblings and peers on pre- and early-teen smoking: A multilevel model. Drug and Alcohol Review, 30(4): 381–387 doi:10.1111/j.1465-3362.2010.00231.x King, B. A., Dube, S. R., & Tynan, M. A. (2012). Secondhand smoke exposure in cars among middle and high school students—United States, 2000–2009. Pediatrics, 129(3). 446–452. doi:10.1542/peds.2011-2307 Mak, K. K., Ho, S. Y., & Day, J. R. (2012). Smoking of parents and best friend—independent and combined effects on adolescent smoking and intention to initiate and quit smoking.Nicotine & Tobacco Research: Official Journal of the Society for Research on Nicotine and Tobacco, 14(9), 1057–1064. doi:10.1093/ntr/nts008; 10.1093/ntr/nts008 McLeroy, K. R., Bibeau, D., Steckler, A., & Glanz, K. (1988). An ecological perspective on health promotion programs. Health Education Quarterly, 15(4, Winter), 351–377. Nebot, M., Tomas, Z., Ariza, C., Valmayor, S., Lopez, M. J., & Juarez, O. (2004). Factors associated with smoking onset: 3-year cohort study of schoolchildren. (Factores asociados con el ini-
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cio del tabaquismo: Seguimiento a los 3 anos de una cohorte de escolares) Archivos De Bronconeumologia, 40(11), 495–501. O’Loughlin, J., Karp, I., Koulis, T., Paradis, G., & Difranza, J. (2009). Determinants of first puff and daily cigarette smoking in adolescents. American Journal of Epidemiology, 170(5), 585–597. doi:10.1093/aje/kwp179; 10.1093/aje/kwp179 Olufajo, O. A., & Agaku, I. T. (2014). Assessment of secondhand smoke exposure at school among US middle and high school students. Journal of School Nursing, pii: 1059840514537075. Salgado-Garcia, F. I., Cooper, T. V., & Taylor, T. (2013). Craving effect of smoking cues in smoking and antismoking stimuli in light smokers. Addictive Behaviors, 38(10), 2492–2499. doi:10.1016/j.addbeh.2013.04.008; 10.1016/j.addbeh.2013.04. 008 US Department of Health and Human Services. (2006). The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. US Department of Health and Human Services (2012). Preventing tobacco use among youth and young adults: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. US Department of Health and Human Services. (2014). The health consequences of smoking: 50 years of progress. A report of the surgeon general. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. Wilson-Frederick, S. M., Williams, C. D., Garza, M. A., NavasAcien, A., Emerson, M. R., Ahmed, S., & Ford, J. G. (2011). Association of secondhand smoke exposure with nicotine dependence among black smokers. Addictive Behaviors, 36(4), 412–415. doi:10.1016/j.addbeh.2010.12.005; 10.1016/j.addbeh. 2010.12.005 World Bank Group (2011). Zambia: country brief. Washington, DC: World Bank Group. Retrieved April 4, 2013, from http://web.worldbank.org/ World Health Organization. (2003).WHO framework convention on tobacco control. Retrieved September 23, 2012, from http://whqlibdoc.who.int/publications/2003/9241591013.pdf World Health Organization. (2011). Global youth tobacco survey, Retrieved July 5, 2014, from http://apps.nccd.cdc.gov/gtssdata/ Ancillary/DataReports.aspx?CAID=1 World Health Organization. (2013). WHO report on the global tobacco epidemic, 2013. Enforcing bans on tobacco advertising, promotion and sponsorship. Retrieved December 10, 2013, from http://apps.who.int/202A1F3B-6F1E-4162-96E2979BCB3B5F15/FinalDownload/DownloadId-BD5DACF211 A245F200FD6C52B616EE29/202A1F3B-6F1E-4162-96E2979BCB3B5F15/iris/bitstream/10665/85380/1/978924150587 1 eng.pdf
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ORIGINAL ARTICLE
The Relationship Between Secondhand Smoke Exposure, Pro-Tobacco Social Influences, and Smoking Susceptibility Among Nonsmoking Zambian Adolescents Israel Terungwa Agaku1 , Tino Maliselo2 and Olalekan A. Ayo-Yusuf2,3 1
Center for Global Tobacco Control, Harvard School of Public Health, Boston, Massachusetts, USA; 2 School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa; 3 Sefako Makgatho Health Sciences University, Medunsa, Pretoria ing laws (World Health Organization, 2003, 2013). For example, even though a national smoke-free law exists prohibiting smoking in public places—including healthcare facilities, public transit, universities, and government facilities—compliance is generally only moderate although some success has been reported recently in the capital city (Lusaka) regarding enforcement of the smokefree law (Drope 2010; World Health Organization, 2013). Protecting nonsmokers from secondhand smoke (SHS) is a public health priority because SHS is a potent health hazard that has been causally linked to a plethora of disease conditions, including lung cancer and stroke among adults, as well as middle ear disease and sudden infant death syndrome among children (US Department of Health and Human Services, 2006, 2014). Children and adolescents are particularly susceptible to SHS exposure because of their having less control over environments where smoking may be occurring such as in the family car or at home, and also being less likely to be aware of the dangers of SHS exposure compared to adults. Adolescents may be susceptible to being exposed to SHS from several sources, including at school, in private cars, and at home, especially in the absence of smokefree rules (Cartmell et al., 2011; King, Dube, & Tynan, 2012; Olufajo & Agaku, 2014). The degree of overall SHS exposure among nonsmoking adolescents could reflect underlying exposure to different behavioral, environmental, and social pro-tobacco influences, such as living with a smoker or having smoking friends—factors which have been shown to predict smoking among youths (US Department of Health and Human Services, 2012). Hence, we hypothesized that the frequency or extent of self-reported SHS exposure among adolescents would be associated with their overall exposure to pro-tobacco social influences and, in turn, with their susceptibility to
Background: We tested the hypothesis that the extent of secondhand smoke (SHS) exposure among nonsmoking adolescents would be associated with their overall exposure to pro-tobacco social influences. Methods: Data were analyzed using descriptive and multivariate methods from the 2011 Zambia Global Youth Tobacco Survey. Results: The odds of SHS exposure increased with increasing exposure to pro-tobacco advertisements. About 39.5% of the gap in SHS exposure between nonsmokers with low versus high smoking susceptibility was attributable to differences in parental or peer smoking. Conclusions: Sustained efforts are needed to denormalize tobacco use in order to reduce youth susceptibility to tobacco use. Keywords secondhand smoke, adolescents, cigarettes, tobacco, smoking, susceptibility
INTRODUCTION
Zambia—a lower middle-income country in the World Health Organization (WHO) African region with a population of approximately 13 million people—is fast becoming a major tobacco leaf producer in the region (Central Statistical Office, Republic of Zambia, 2011; Drope, 2010; World Bank, 2011). Tobacco use is a significant public health problem in the country; the prevalence of daily cigarette smoking among adults was 11% during 2011, while the prevalence of current cigarette smoking among adolescents aged 13–15 years was 6.2% during the same year (World Health Organization, 2011, 2013). Although Zambia became a party to the WHO Framework Convention on Tobacco Control on May 23, 2008, the tobacco control legislative environment is still relatively weak, with little enforcement of exist-
Address correspondence to Dr Israel Terungwa Agaku, Harvard School of Public Health, Center for Global Tobacco Control, 677 Huntington Avenue, Boston, MA 02125, USA. Email: [email protected]
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smoking. To test this hypothesis, we analyzed data from the Global Youth Tobacco Survey (GYTS) for Zambia during 2011 to measure the relationship between SHS exposure, pro-tobacco social influences, and smoking susceptibility among Zambian adolescents. METHODS Data Source
Data were obtained from the 2011 National Zambia GYTS. A two-stage cluster sample design was used to produce representative data for the country. At the first stage, schools were selected with probability proportional to enrollment size. At the second stage, classes were randomly selected and all students in selected classes were eligible to participate. A total of 3,377 male and female students in grades 7, 8, and 9 (ages ranging from 11 to 16 years or older) completed the self-administered questionnaires in classrooms, yielding an overall response rate of 55.7%. Measures
Secondhand Smoke Exposure Secondhand smoke exposure was assessed with the following three questions: “During the past 7 days, on how many days have people smoked in your home or in your presence?”; “During the past 7 days, on how many days have people smoked in your presence, in enclosed public places?”; and “During the past 7 days, on how many days have people smoked in your presence, in outdoor public places?” For all the three questions, categorical response options were: “0” days; “1 to 2” days; “3 to 4” days; “5 to 6” days; or “7” days. Any response other than “0” days was categorized as being exposed to SHS in the respective environment assessed. For our analyses, we categorized respondents as having any SHS exposure if they reported being exposed to SHS from at least one of the three environments assessed (i.e., home; enclosed public places; or outdoor public places). Respondents with missing observations for any of the three environments (4.0%) were excluded from the analyses. Cigarette Smoking Status and Smoking Susceptibility Ever cigarette smokers were students who reported that they had experimented with cigarette smoking, even one or two puffs during their lifetime. Those who had never experimented with cigarette smoking were categorized as never smokers. Current cigarette smokers were students who reported smoking cigarettes on at least one day within the past 30 days. Former cigarette smokers were students who reported ever smoking cigarettes during their lifetime but did not report smoking a cigarette within the past 30 days. Both never and former smokers were categorized as current nonsmokers. Respondents were asked two questions to assess their smoking intentions: “At any time during the next 12 months, do you think you will smoke a cigarette?” and “If one of your best friends offered you a cigarette, would you smoke it?” Categorical response options to both questions were: “definitely not,” “probably not,” “probably yes,” or “definitely yes.” Nonsmokers were classified as
being highly susceptible to cigarette smoking if they responded in any way other than “definitely not” to either question. On the other hand, nonsmokers who expressed a firm conviction not to smoke cigarettes (i.e., a response of “definitely not” to both questions) were categorized as having low susceptibility to cigarette smoking. Perception about the social acceptability of cigarette smoking was assessed with the following question: “Does smoking cigarettes help people feel more or less comfortable at celebrations, parties, or in social gatherings?” Categorical responses included the following: “More comfortable,” “less comfortable,” or “no difference from nonsmokers.” Pro-tobacco Social Influences In line with the socio-ecological model (McLeroy, Bibeau, Steckler, & Glanz, 1988), we measured several levels of pro-tobacco social influences, including proximal or inter-personal factors, as well as more distal or environmental factors. Proximal pro-tobacco influences assessed included parental and peer smoking, both categorized as having at least one parent or close friend that smoked cigarettes, versus none that smoked. Environmental pro-tobacco influences assessed included exposure to tobacco advertisements from six different media, namely: movies; television programs; retail stores; billboards; newspapers/magazines; and outdoor community events such as fairs, concerts, or sporting events. Within the survey, respondents could select one of the three response options that best described their frequency of exposure to each of the six media assessed. The response options were: (1) “a lot,” (2) “sometimes”/“a few,” or (3) “none”/“never.” Within our analyses, students were categorized as being exposed to a particular advertisement medium if they selected a response option of “sometimes”/“a few,” or “a lot.” On the other hand, students were categorized as being unexposed if they selected a response option of “none”/“never,” or if they reported that they did not use or access the medium of interest at all. Receptivity to pro-tobacco advertisements was defined as a “Yes” response to the following question: “Do you have something (t-shirt, pen, backpack, etc.) with a cigarette brand logo on it?” Statistical Analyses
Data were summarized using descriptive statistics (percentage values) and further analyzed using multivariate logistic regression. Prevalence estimates with relative standard errors of ≥35% were considered statistically unreliable. Comparison of prevalence estimates was performed with the chi-squared statistic (p < .05). The total number of distinct sources of pro-tobacco advertisements that respondents reported being exposed to was added for each student (range: 0 to 6) and included as a variable in the multivariate analyses to assess for a dose-response relationship between environmental pro-tobacco social influences and SHS exposure. In a separate model, a composite variable denoting the total number of distinct environments where respondents were exposed to SHS within the past 7 days (i.e., 0, 1, or ≥2 environments based on
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exposures from home; enclosed public places; or outdoor public places) was included as an independent variable to assess the relationship with smoking susceptibility among nonsmokers. All multivariate analyses controlled for age, sex, and ever smoking status. Differences in SHS exposure by smoking susceptibility status among nonsmokers were further explored using the Blinder–Oaxaca decomposition analysis. All analyses were weighted and performed with Stata version 11 (Stata Corp. 2009, College Station, TX). RESULTS
In total, 50.8% of study participants were girls and age distribution among all respondents was as follows: 11–13 years (25.8%); 14–15 years (42.8%); and ≥16 years (31.5%). Overall smoking prevalence was 7.0%, while prevalence of smoking susceptibility among nonsmokers was 26.7%. Prevalence of SHS Exposure
Approximately 59.5% of all students were exposed to SHS from at least one source. By specific sources of SHS exposure, 33.1% were exposed at home, 42.6% were exposed in enclosed public places, while 45.0% were exposed in outdoor public places. By cigarette smoking status, SHS exposure prevalence was as follows: current cigarette smokers (87.9%), former cigarette smokers (69.6%), never cigarette smokers with high smoking susceptibility (56.3%), and never cigarette smokers with low smoking susceptibility (51.2%). SHS exposure prevalence increased with increasing age, and was lowest among students aged 11–13 years (55.4%) and highest among students aged ≥16 years (61.4%) (Table 1). Students who perceived that smoking made one more comfortable at social events had higher prevalence of any SHS exposure (63.4%) compared with those who believed that smoking made one less comfortable at social events (58.7%) (p < .05). Students who had at least one parent that smoked had a significantly higher prevalence of any SHS exposure (76.5%) compared with those that had no smoking parent (54.8%). Similarly, students with one or more close friends that smoked had a significantly higher prevalence of any SHS exposure (71.6%) compared with those with no close friend that smoked (52.8%). The prevalence of any SHS exposure increased with the number of different pro-tobacco advertisements that students were exposed to, from 30.9% among students who reported not being exposed to any source of pro-tobacco advertisement to 70.1% among students who reported being exposed to all six sources of pro-tobacco advertisements (p < .05). Students who owned a tobacco-branded item had a significantly higher prevalence of any SHS exposure (69.5%) compared with those with no tobacco-branded item (56.0%). Relationship Between SHS Exposure and Exposure to Pro-Tobacco Social Influences
Within adjusted analyses, nonsmokers with high smoking susceptibility had higher odds of any SHS exposure
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compared with those with low smoking susceptibility (adjusted odds ratio [aOR] = 1.26; 95% confidence interval [CI]: 1.04–1.53). Nonsmokers who had one or both parents as smokers (aOR = 2.02; 95% CI: 1.59–2.57), or one or more close friends as smokers (aOR = 1.68; 95% CI: 1.39–2.03), had higher odds of being exposed to SHS compared with those that had no smoking parents or close friends respectively. As shown in Table 2, a dose-response gradient was observed in the adjusted relationship between exposure to pro-tobacco advertisements, and the odds of exposure to any SHS among nonsmokers. Compared with nonsmokers who were not exposed to any pro-tobacco advertisements, increased odds of any SHS exposure were observed among nonsmokers who were exposed to one (aOR = 1.32), two (aOR = 2.47), three (aOR = 3.27), four (aOR = 4.12), five (aOR = 5.37), or all six sources of protobacco advertisements (aOR = 5.76) (all p-values < .05). Similarly, nonsmokers that owned a tobacco-branded item had higher odds of being exposed to any SHS compared with those with none (aOR = 1.39; 95% CI: 1.10–1.76). Nonsmokers who were exposed to SHS from ≥2 distinct environments had higher odds of being highly susceptible to cigarette smoking compared with those not exposed to SHS from any environment (aOR = 1.43; 95% CI: 1.16–1.77). Similarly, nonsmokers who reported being daily exposed to SHS in home (aOR = 1.57; 95% CI: 1.10–2.25) or at enclosed public areas (aOR = 1.68; 95% CI: 1.22–2.32) had higher odds of being highly susceptible to cigarette smoking compared with those not exposed to SHS on any day in the respective environments (Table 3). In total, 39.5% (95% CI: 25.6–53.5) of the explainable gap in SHS exposure between nonsmokers with low versus high smoking susceptibility was attributable to higher proportions of parental or peer smoking among highly susceptible nonsmokers. Differences in exposure to protobacco advertisements between nonsmokers with low versus high smoking susceptibility (with higher exposure noted among highly susceptible nonsmokers) further accounted for 9.0% (95% CI: 4.0–14.0) of the explainable differences in any SHS exposure In contrast, differences in socio-demographic characteristics, such as age and sex, accounted for only 1.3% (95% CI: 0.1–3.0) of the explainable differences in SHS exposure by smoking susceptibility status among nonsmokers. DISCUSSION
We found a significant association between increasing levels of exposure to pro-tobacco social influences and increased odds of SHS exposure among nonsmokers. Nonsmokers who were exposed to SHS from multiple environments, as well as those who were exposed to SHS on a daily basis at home or in enclosed public places, all had higher odds of being susceptible to cigarette smoking when compared with those unexposed to SHS. While the relationship between SHS exposure and smoking susceptibility among nonsmokers may be partly explained by increased sensitivity to nicotine following continuous
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TABLE 1. Prevalence of any secondhand smoke exposure by smoking status and other selected characteristics, GYTS, Zambia, 2011
Characteristics Total Age (years) 11–13 14–15 ≥16 Sex Boy Girl Perceived social acceptability of smoking at social events Smoking makes one more comfortable Smoking makes one less comfortable No difference between smokers and nonsmokers Parental smoking None smokes One or both smoke Peer smoking None smokes One or all smoke Total number of distinct sources of pro-tobacco advertisement exposures reporteda None One Two Three Four Five Six Receptivity to tobacco advertisements (owning a tobacco-branded item) None One or more
Never cigarette Never cigarette smokers with low smokers with high smoking smoking susceptibility, susceptibility, n = n = 533 % (95% CI) 1,604 % (95% CI)
Overall N = 3,315 % (95% CI)
Current cigarette smokers n = 186 % (95% CI)
Former cigarette smokers n = 331 % (95% CI)
59.5 (57.8–61.2)
87.9 (83.0–92.7)
69.6 (64.5–74.6)
56.3 (52.0–60.6)
51.2 (48.7–53.6)
55.4 (52.0–58.8) 60.6 (58.1–63.2) 61.4 (58.4–64.4)
88.9 (77.0–100.0) 86.3 (78.4–94.2) 90.0 (83.0–97.0)
71.6 (61.3–81.9) 68.6 (60.8–76.4) 70.9 (62.1–79.7)
57.6 (48.7–66.5) 53.2 (46.6–59.9) 58.9 (51.6–66.2)
44.5 (39.9–49.2) 55.8 (52.1–59.5) 50.7 (45.9–55.5)
60.2 (57.7–62.6) 58.3 (55.9–60.7)
85.9 (78.7–93.0) 90.4 (83.7–97.2)
69.3 (62.2–76.4) 69.2 (61.7–76.7)
54.7 (48.6–60.7) 57.3 (51.1–63.4)
51.4 (47.8–55.0) 50.6 (47.2–54.0)
63.4 (60.4–66.3)
93.1 (86.6–99.6)
71.8 (63.2–80.5)
60.1 (52.7–67.5)
53.9 (49.3–58.4)
58.7 (56.1–61.3)
89.6 (82.2–96.9)
68.8 (60.7–76.9)
61.3 (54.8–67.9)
50.8 (47.2–54.4)
55.8 (52.2–59.3)
79.5 (67.6–91.5)
68.3 (58.2–78.4)
43.0 (34.2–51.8)
49.5 (43.9–55.1)
54.8 (52.9–56.8) 76.5 (73.4–79.7)
83.3 (75.6–91.0) 94.9 (90.0–99.8)
66.4 (60.2–72.5) 79.1 (70.5–87.7)
52.4 (47.5–57.3) 71.2 (62.7–79.6)
49.6 (47.0–52.2) 64.8 (57.8–71.8)
52.8 (50.7–55.0) 71.6 (69.0–74.2)
83.7 (73.3–94.0) 89.3 (83.9–94.8)
64.0 (56.8–71.1) 76.1 (69.0–83.1)
50.3 (44.9–55.8) 66.8 (60.0–73.7)
49.4 (46.6–52.2) 59.8 (54.5–65.1)
30.9 (23.6–38.3) 38.5 (32.7–44.3) 54.0 (49.5–58.6) 60.1 (56.2–64.1) 65.9 (62.0–69.7) 69.5 (65.4–73.6) 70.1 (64.9–75.4)
. . .b 83.3 (62.2–100.0) 76.5 (56.3–96.6) 83.3 (70.0–96.7) 92.1 (83.5–100.0) 88.0 (75.3–100.0) 95.2 (86.1–100.0)
. . .b 52.9 (29.2–76.7) 62.8 (48.3–77.2) 67.2 (55.4–79.0) 75.0 (63.7–86.3) 69.1 (56.9–81.3) 80.0 (67.6–92.4)
27.3 (8.7–45.9) 40.0 (26.4–53.6) 53.1 (40.9–65.4) 60.0 (50.4–69.6) 57.7 (47.9–67.6) 66.7 (56.4–76.9) 72.1 (58.7–85.5)
28.4 (19.3–37.5) 29.1 (22.0–36.2) 45.8 (39.3–52.3) 49.4 (43.4–55.5) 58.6 (52.7–64.6) 66.1 (60.3–72.0) 65.6 (58.0–73.1)
56.0 (54.0–58.0) 69.5 (65.8–73.1)
85.1 (77.9–92.3) 89.8 (82.1–97.5)
64.8 (58.4–71.2) 79.0 (70.1–87.9)
54.3 (49.3–59.3) 63.5 (53.9–73.2)
50.8 (48.2–53.5) 53.4 (46.0–60.7)
Notes. Any secondhand smoke exposure was defined as a report by a student that they were exposed to tobacco smoke at any of the following places: home, enclosed public areas, or outdoor public areas. GYTS = Global Youth Tobacco Survey; CI = confidence interval. a Total number of pro-tobacco advertisements was calculated by counting the total number of pro-tobacco advertisements reported by respondents from the six different sources assessed in the survey. These sources included: movies, television programs, retail stores, billboards, newspapers/magazines, and outdoor community events such as fairs or sporting events. b Statistically unreliable estimates, with relative standard errors ≥35%.
and prolonged exposure to SHS (Wilson-Frederick et al., 2011), the extent of SHS exposure may largely be a proxy for the extent of exposure to powerful pro-tobacco social influences which may mold adolescent nonsmokers’ perception of smoking as normative. This is supported by the fact that the majority of the explainable differences in SHS exposure by smoking susceptibility status in our study was accounted for by parental and peer smoking. These findings may have some implications for tobacco screening and counseling among youths in order to target those at high risk for smoking initiation. Thus, in addition
to asking adolescents if they currently use tobacco, asking them about their frequency of SHS exposure within the past week, or the different environments in which they were exposed to SHS may potentially help to identify nonsmokers who may be susceptible to cigarette smoking. The role of parental and peer smoking on smoking susceptibility and initiation has been well documented in the scientific literature (Kelly et al., 2010; Mak, Ho, & Day, 2012; US Department of Health and Human Services, 2012). Parent’s smoking habit may influence adolescents’ attitude toward smoking as an acceptable norm
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TABLE 2. Crude and adjusted relationship between pro-tobacco social influences and any secondhand smoke exposure among current nonsmokers, GYTS, Zambia, 2011 Characteristic Smoking susceptibility Low High Perceived social acceptability of smoking at social events Smoking makes one more comfortable Smoking makes one less comfortable No difference between smokers and nonsmokers Parental smoking None smokes One or both smoke Peer smoking None smokes One or all smoke Total number of distinct sources of pro-tobacco advertisement exposures reporteda None One Two Three Four Five Six Receptivity to tobacco advertisements (owning a tobacco-branded item) None One or more
Crude effect on secondhand smoke exposure, cOR (95% CI)
Adjusted effect on secondhand smoke exposure, aOR (95% CI)
1.00 (referent) 1.34 (1.11–1.62)
1.00 (referent) 1.26(1.04–1.53)∗
1.00 (referent) 0.89 (0.74–1.08) 0.75 (0.60–0.94)
1.00 (referent) 0.89 (0.74–1.08) 0.74 (0.58–0.91)∗
1.00 (referent) 2.13 (1.69–2.69)
1.00 (referent) 2.02 (1.59–2.57)∗
1.00 (referent) 1.81 (1.51–2.18)
1.00 (referent) 1.68 (1.39–2.03)∗
1.00 (referent) 1.29 (0.80–2.09) 2.53 (1.62–3.94) 3.08 (2.00–4.75) 3.99 (2.58–6.18) 5.22 (3.35–8.13) 5.78 (3.58–9.32)
1.00 (referent) 1.32 (0.81–2.15) 2.47 (1.57–3.89)∗ 3.27 (2.09–5.10)∗ 4.12 (2.63–6.45)∗ 5.37 (3.41–8.45)∗ 5.76 (3.53–9.40)∗
1.00 (referent) 1.45 (1.15–1.82)
1.00 (referent) 1.39 (1.10–1.76)∗
Notes. Any secondhand smoke exposure was defined as a report by a student that they were exposed to tobacco smoke at any of the following places: home, enclosed public areas, or outdoor public areas. GYTS = Global Youth Tobacco Survey; cOR = crude odds ratio; aOR = adjusted odds ratio; CI = confidence interval. a Total number of pro-tobacco advertisements was calculated by counting the total number of pro-tobacco advertisements reported by respondents from the six different sources assessed in the survey. These sources included: movies, television programs, retail stores, billboards, newspapers/magazines, and outdoor community events such as fairs or sporting events. ∗ Statistically significant adjusted odds ratios. Multivariate analyses adjusted for age, sex, and ever smoking status.
(Mak et al., 2012; Nebot et al., 2004; O’Loughlin et al., 2009). Parents who smoke may also be less restrictive on their own children picking up smoking habits (Brown et al., 2010). More so, children of parents who smoke may have easier access to cigarettes at home and learn smoking behavior by imitating their parents in line with the social learning theory. Similarly, having friends who are smokers may increase smoking susceptibility among adolescents because of peer pressure to conform or for the feeling
of acceptance (Brown et al., 2010). In addition, hanging around with friends who smoke or being present at social events where smoking is occurring may serve as cues that may prompt smoking relapse among former smokers (Salgado-Garcia, Cooper, & Taylor, 2013). These findings underscore the need for stronger measures to denormalize tobacco use and reduce adolescent exposure to pro-tobacco social influences, including tobacco advertising and promotion. According to the WHO
TABLE 3. Relationship between smoking susceptibility and the number of days of secondhand smoke exposure among current nonsmokers in different environments, GYTS, Zambia, 2011 Adjusted effect on Smoking susceptibility Number of days of secondhand smoke exposure within past 7 days
Exposure source: home aOR (95% CI)
Exposure source: enclosed public areas aOR (95% CI)
Exposure source: outdoor public areas aOR (95% CI)
0 days 1 to 2 days 3 to 4 days 5 to 6 days 7 days
1.00 (referent) 1.25 (0.93–1.69) 0.92 (0.58–1.45) 1.27 (0.76–2.11) 1.57 (1.10–2.25)∗
1.00 (referent) 1.24 (0.96–1.59) 1.33 (0.90–1.96) 1.42 (0.92–2.21) 1.68 (1.22–2.32)∗
1.00 (referent) 0.86 (0.66–1.12) 1.20 (0.84–1.73) 1.53 (1.01–2.33)∗ 1.35 (1.00–1.83)
Notes. GYTS = Global Youth Tobacco Survey; aOR = adjusted odds ratio; CI = confidence interval. ∗ Statistically significant adjusted odds ratios. Multivariate analyses adjusted for age, sex, and ever smoking status.
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report (2013) on the global tobacco epidemic, no national bans currently exist in Zambia on tobacco advertising on national/international television, radio, newspapers/magazines, points-of-sale, billboards, or other forms of outdoor advertising. Previous studies have shown a significant relationship between increased exposure to pro-tobacco advertisements and increased susceptibility, as well as actual experimentation with tobacco products (Agaku & Ayo-Yusuf, 2013; Dube, Arrazola, Lee, Engstrom, & Malarcher, 2013). Adolescents in particular are more receptive to tobacco promotional activities than adults, thus emphasizing the need for stronger restrictions in youth-targeted tobacco advertisements (Andrews, Netemeyer, Burton, Moberg, & Christiansen, 2004; US Department of Health and Human Services, 2012). The findings in this study are subject to some limitations. First, SHS exposure was self-reported and may have been subject to misreporting. However, recall was limited to the past 7 days, a relatively short period. Second, other determinants of increased smoking susceptibility and SHS exposure were not assessed due to lack of data, including sibling and teacher smoking. Third, the cross-sectional nature of the data precludes any causal inferences and only associations can be deduced. Finally, the study may be limited in generalizability to other countries with stronger comprehensive tobacco control programs, especially with regard to SHS exposure in public areas.
THE AUTHORS Dr. Israel Terungwa Agaku, conducts epidemiologic research on tobacco products with a focus on the contribution to dependence and abuse liability, particularly among adolescents and young adults.
Dr Tino is a public health practitioner working with the Zambian Ministry of Health and his research interest is in tobacco control advocacy.
Professor Olalekan A Ayo-Yusuf is a Dean at the University of Limpopo and his research interest is in studying alternative tobacco use and tobacco control policy.
CONCLUSIONS
This study demonstrated that SHS exposure among Zambian adolescents was associated with smoking susceptibility and exposure to pro-tobacco social influences. These findings highlight the need for multilevel approaches in adolescent tobacco use prevention interventions. In particular, the results underscore the need for stronger restrictions on tobacco advertising that targets youths. Stronger enforcement of smoke-free bans may also help protect nonsmoking youths and adults from involuntary exposure to SHS and help to denormalize tobacco use.
Declaration of Interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article. Dr. Israel Agaku initiated the reported research while affiliated with the Center for Global Tobacco Control at Harvard University. He is currently affiliated with the Centers for Disease Control and Prevention’s Office on Smoking and Health. The research in this report was completed and submitted outside of the official duties of his current position and does not reflect the official policies or positions of the Centers for Disease Control and Prevention.
GLOSSARY
Pro-tobacco social influences: Social factors that may catalyze smoking initiation or progression. As used in this study, this encompasses both proximal influences (e.g., parental and peer smoking) and environmental influences (e.g., exposure to pro-tobacco advertising). Secondhand smoke: Tobacco smoke exhaled from someone smoking or produced by a smoldering cigarette and involuntarily inhaled by a nonsmoker. Smoking susceptibility: A lack of a firm conviction not to smoke a cigarette in the future, or if offered by a close friend.
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