Nicotine & Tobacco Research, Volume 16, Number 6 (June 2014) 663–671
Original Investigation
Secondhand Smoke Exposure in Cars and Rooms: Trend Comparisons Among Subpopulations of Nonsmoking U.S. Middle and High School Students Russell K. McIntire PhD, MPH1, Jonathan T. Macy PhD, MPH1, Dong-Chul Seo PhD1, Ashlyn A. Nelson PhD2, Lloyd J. Kolbe PhD1 1Department of Applied Health Science, Indiana University School of Public Health-Bloomington, Bloomington, IN; 2School of Public and Environmental Affairs, Indiana University, Bloomington, IN
Received June 24, 2013; accepted November 18, 2013
Abstract Introduction: Young people in the United States are exposed to secondhand smoke (SHS) primarily in 2 settings: homes and cars. Recently, researchers reported that the prevalence of U.S students exposed to SHS in cars decreased from 2000 to 2009; however, comparisons of trends across school levels, gender, and racial/ethnic groups were not assessed. Moreover, no studies have examined trends of exposure to SHS in rooms. Methods: We used data from the 2000, 2002, 2004, 2006, and 2009 waves of the National Youth Tobacco Survey, a nationally representative cross-sectional survey of U.S. middle and high school students. For SHS in cars and rooms, we identified exposure trends among nonsmokers from 2000 to 2009 and compared trends across subpopulations with binary logistic regression. Results: We identified significant downward linear trends in SHS in cars and rooms for nearly all measured subpopulations of nonsmoking students from 2000 to 2009. SHS exposure in cars and rooms declined at a significantly greater rate for males than for females. SHS exposure in cars declined at a significantly greater rate for non-Hispanic (NH) Blacks than for NH Whites. SHS exposure in rooms declined at a significantly greater rate for NH Whites than for Hispanics and Native Hawaiians/Pacific Islanders. Conclusions: Although prevalence of exposure to SHS in cars and rooms among nonsmoking U.S. middle and high school students has declined from 2000 to 2009, the rates of decline were not equal across genders and racial/ethnic groups. Identification of these differing rates of exposure can help the public health community advocate for interventions focused on reducing adolescent SHS exposure.
Introduction Secondhand smoke (SHS), which is composed of both mainstream smoke exhaled by smokers and sidestream smoke produced by the burning end of tobacco products, is the cause of considerable morbidity and mortality. The U.S. Centers for Disease Control and Prevention (CDC) identified that SHS causes an estimated 49,400 deaths among U.S. nonsmokers per year (CDC, 2008a). U.S. Surgeon Generals’ Reports (U.S. Department of Health and Human Services [DHHS], 2006, 2010) concluded that SHS negatively affects almost every organ in the body and causes lung cancer, heart disease, bronchitis, pneumonia, thrombosis, and sudden infant death syndrome. In the United States, tobacco control efforts such as media campaigns and laws that prohibit smoking in public places have been successful in reducing SHS exposure, but the results have
not been equal for all population groups. For example, SHS exposure in the general population has declined by 70% since 1988, but children have experienced significantly less decline (CDC, 2008b; DHHS, 2006). Studies estimate that more than one in five children in the United States are exposed to SHS each day (DHHS, 2006; McCausland et al., 2005), with higher levels of exposure among younger children compared with older children and among non-Hispanic (NH) Whites and NH Blacks compared with Mexican-American children (Marano, Schober, Brody, & Zhang, 2009). SHS exposure among children occurs primarily in two settings: in the family home and in vehicles (consistent with prior studies, “vehicles” will be referred to as “cars”) (DHHS, 2006; Jarvie & Malone, 2008; Jordan, Price, Dake, & Shah, 2005). While homes and workplaces have been shown to be the predominant location for exposure to SHS, studies have shown
doi:10.1093/ntr/ntt207 Advance Access publication December 24, 2013 © The Author 2013. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: [email protected].
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Corresponding Author: Jonathan T. Macy, PhD, MPH, Department of Applied Health Science, Indiana University School of Public Health-Bloomington, 1025 East 7th Street, Room 116, Bloomington, IN 47405, USA. Telephone: 812-856-0704; Fax: 812-855-3936; E-mail: [email protected]
SHS exposure in cars and in rooms
664
exposed daily to SHS in rooms, whereas 7% were exposed daily to SHS in cars. Like SHS in cars, we hypothesized that prevalence of SHS in rooms declined for subpopulations from 2000 to 2009 and that there would be no differences in trends of SHS in rooms across genders, school levels, and race/ ethnicities.
Methods Data Source The NYTS measures tobacco-use behaviors, exposure to SHS, smoking cessation, tobacco-related school curriculum, minors’ ability to purchase or obtain tobacco products, attitudes about tobacco, and familiarity with pro- and antitobacco media messages among middle and high school students in the United States (CDC, 2009). To compare trends of SHS exposure among adolescent subpopulations, we used data from five comparable NYTS studies conducted during the springs of 2000, 2002, 2004, 2006, and 2009. We chose not to include data from the 2011 wave of the NYTS because the items for the two main dependent variables were modified for 2011 and are thus not comparable with previous NYTS data. During administrations of the NYTS, participants were asked to complete an anonymous pencil and paper questionnaire in a classroom setting. Participation in all surveys was voluntary at both the school and student level, and no incentives were provided for student participation. Schools used either passive or active permission forms at their discretion to ensure that parents had the option to decline their child’s participation. Prior to data collection, standardized procedures were used to recruit and train data collectors. Sample The NYTS utilized a geographically stratified three-stage cluster sampling design to create nationally representative cross-sectional samples of students attending public and private middle schools (defined as grades 6th, 7th, and 8th) and high schools (defined as grades 9th, 10th, 11th, and 12th) in the 50 states and in Washington, DC (CDC, 2009). Samples were probabilistic and collected without replacement in the following three stages: 1) primary sampling units consisting of counties, groups of small adjacent counties, or a portion of a large county; 2) public or private schools containing eligible grades within Stage 1; and 3) students via whole classrooms within each selected school (CDC, 2009). NYTS data were adjusted for nonresponse and weighted to provide national prevalence estimates for the years of survey administration. The weighting procedure is described in detail elsewhere (CDC, 2004, 2006, 2009). During 2000–2009, small modifications were made in NYTS sampling designs. Despite these modifications, sampling designs enabled comparisons across survey years (Duke et al., 2010; King et al., 2012; CDC, 2010b). The total number of schools that participated in the NYTS data collection waves ranged from 205 in 2009 to 324 in 2000. The total number of students that participated in survey years ranged from 22,679 in 2009 to 35,824 in 2000. The overall response rates for the NYTS surveys ranged from 75% in 2002 to 85% in 2009 (CDC, 2009).
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that the car setting poses a distinct risk for child SHS exposure given the high concentration of smoke that is produced within a car in which passengers are smoking (Ott, Klepeis, & Switzer, 2008; Rees & Connolly, 2006; Semple et al., 2012; Sendzik, Fong, Travers, & Hyland, 2009). While the overwhelming majority of setting-specific SHS interventions focus on the home as the exposure site, media and educational campaigns have been launched at national (American Legacy Foundation, 2005, January 11) and state (Americans for Nonsmokers’ Rights [ANR], 2013, August 28) levels to encourage parents to make not just their homes but also their cars smoke-free. In addition, U.S. states and jurisdictions have enacted legislation to protect children from SHS in cars. In April 2006, Arkansas became the first state to pass a law making smoking in private cars carrying children a punishable offense (CDC, 2012). Shortly thereafter in 2006, Louisiana passed a similar law, followed by California in 2008, and Maine in 2009 (CDC, 2012). Most recently, Utah and Oregon passed laws banning smoking in vehicles in the presence of children effective May 2013 and January 2014, respectively (ANR, 2013, July 26). Although smoke-filled cars have been identified as highrisk environments for children, only a few studies have analyzed the frequency of SHS in cars among nationally representative samples of U.S. children (King, Dube, & Tynan, 2012; McCausland et al., 2005). One study (McCausland et al., 2005) found the prevalence of daily exposure to SHS in cars among U.S middle and high school students declined 37% between 1999 and 2003. The study reported that in 2003, 7% of middle and high school students were exposed daily to SHS in cars. Using data from the National Youth Tobacco Survey (NYTS), King et al. (2012) showed that the prevalence of U.S adolescent SHS in cars decreased from 2000 to 2009 among all demographic subpopulations of smoking and nonsmoking school students. Despite these downward trends, in 2009, over one fifth of nonsmoking middle and high school students were exposed to SHS in cars at least once in the past week. While King et al. (2012) identified reductions in prevalence of SHS in cars among all measured adolescent demographic subpopulations from 2000 to 2009, they did not test whether there were significant differences in trends of adolescent SHS in cars across these subpopulations. This information would be helpful to determine if any of these subpopulations might warrant particular attention as part of SHS-reduction strategies. Therefore, in this study, we used NYTS data to identify the prevalence and trends of SHS in cars among demographic subpopulations of nonsmoking U.S. school students from 2000 to 2009 and then tested whether there were significant differences in trends across genders, school levels, and race/ethnicities. Since public health interventions at the national level have not focused on reducing SHS in cars among specific demographic subpopulations of U.S. adolescents, we hypothesized that there would be no differences in SHS in cars trends from 2000 to 2009 across genders, school levels, and race/ethnicities. Finally, we also explored the prevalence and trends of adolescent exposure to SHS in rooms. Although studies have identified recent increases in workplace smoking bans and voluntary home smoking rules, millions are still exposed to SHS in these locations (DHHS, 2006; King, Dube, & Homa, 2013). Like SHS in cars, few studies have focused on SHS in rooms, and even fewer have explored both SHS in cars and SHS in rooms. A notable exception is the McCausland et al. (2005) study that reported that 13% of U.S. adolescents were
Nicotine & Tobacco Research female), and race/ethnicity (NH White, NH Black, Hispanic, NH Asian, NH American Indian/Alaskan Native, NH Native Hawaiian/Pacific Islander). We dichotomized the grade variable into a school level variable reflecting middle school (6th, 7th, and 8th grades) or high school (9th, 10th, 11th, and 12th grades). We coded all participants reporting “ungraded or no grade” as missing.
Our analyses included only those students who self-identified as nonsmokers. Nonsmokers were defined as participants who answered “0 days” to the following question: “During the past 30 days, on how many days did you smoke cigarettes?” Of the 139,627 participants contained in the five datasets, 114,200 (84.7%) were nonsmokers. Of the nonsmokers, the percent of respondents excluded due to missing data for the dependent variables (SHS in cars and SHS in rooms) from the survey years ranged from 0.9% to 3.8% for SHS in cars and 1.9% to 3.7% for SHS in rooms. The resulting sample sizes for the survey years are found in Table 1. Demographic characteristics of the cross-sectional samples, shown in Table 1, were similar across all of the survey administrations.
Statistical Analyses
Measures SHS in Cars and Rooms The NYTS assessed SHS in cars and SHS in rooms, respectively, using the following two items: “During the past 7 days, on how many days did you ride in a car with someone who was smoking cigarettes?” and “During the past 7 days, on how many days were you in the same room with someone who was smoking cigarettes?” Responses to these items were amalgamated by CDC on an ordinal scale indicating increasing frequency of exposure: “0 days,” “1 or 2 days,” “3 or 4 days,” “5 or 6 days,” or “7 days.” For both the SHS in cars and SHS in rooms variables, we treated participants as exposed if they reported exposure on at least one of the past 7 days. Linear Trend Variable In order to account for the nonconsecutive variations between survey years, the CDC used orthogonal polynomials to create coefficients representing each year of survey administration to aid in the trend analysis (King et al., 2012). We used these coefficients to create the continuous linear variable in order to identify and compare trends.
Results Prevalence and Trend Analyses Table 2 shows the prevalence of SHS in cars for the total population and all measured subpopulations of nonsmoking middle and high school students for all NYTS administrations. In 2000, 39.0% of middle and high school students were exposed to SHS in cars, whereas in 2009, 22.8% of students were exposed to SHS in cars. Logistic regression analyses identified
Demographics NYTS participants reported their age, grade (6th, 7th, 8th, 9th, 10th, 11th, 12th, ungraded, or no grade), gender (male or
Table 1. Demographic Characteristics of Cross-Sectional Samples: NYTS 2000, 2002, 2004, 2006, and 2009
Variable Gender Male Female Grade level Middle High Race/ethnicity NH White NH Black Hispanic NH Asian NH AI/AN NH NH/PI
2000
2002
2004
2006
2009
Total
n (%)
n (%)
n (%)
n (%)
n (%)
n (%)
13,771 (49.5) 14,048 (50.5)
10,430 (48.91) 10,894 (51.09)
11,204 (48.83) 11,741 (51.17)
10,802 (47.75) 11,818 (52.25)
9,274 (48.51) 9,842 (51.49)
55,481 (48.74) 58,343 (51.26)
14,025 (50.48) 13,757 (49.52)
10,971 (51.51) 10,326 (48.49)
12,314 (53.56) 10,678 (46.44)
11,188 (49.28) 11,516 (50.72)
9,380 (49.09) 9,727 (50.91)
57,878 (50.82) 56,004 (49.18)
14,675 (53.33) 4,688 (17.04) 5,984 (21.74) 1,400 (5.09) 451 (1.64) 321 (1.17)
10,078 (47.59) 4,214 (19.90) 5,240 (24.74) 1,129 (5.33) 286 (1.35) 229 (1.08)
10,353 (46.56) 4,443 (19.98) 5,852 (26.32) 1,166 (5.24) 264 (1.19) 158 (0.71)
9,720 (43.81) 4,663 (21.02) 6,007 (27.08) 1,307 (5.89) 243 (1.10) 245 (1.10)
9,100 (49.01) 3,157 (17.00) 5,196 (27.99) 800 (4.31) 207 (1.11) 107 (0.58)
53,926 (48.28) 21,165 (18.95) 28,279 (25.32) 5,802 (5.20) 1,451 (1.30) 1,060 (0.95)
Note. AI/AN = American Indian/Alaska Native; NH = non-Hispanic; NH/PI = Native Hawaiian/Pacific Islander; NYTS = National Youth Tobacco Survey.
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We used sampling information (survey weights, strata, and primary sampling units) provided by the NYTS methodology reports to adjust for the complex survey design and to produce population estimates for SHS in cars and SHS in rooms for each measured year from 2000 to 2009 (CDC, 2009). We generated descriptive statistics to identify prevalence estimates of SHS in cars and SHS in rooms with 95% CIs in each survey year. We then determined linear trends by interpreting the coefficient of the linear variable in binary logistic regression models. All logistic regression models controlled for gender, school level, and race/ethnicity in order to account for changes in these variables across survey years. To compare linear trends of SHS in cars and SHS in rooms across subpopulations, we generated two binary logistic regression models, one for SHS in cars and one for SHS in rooms. We compared linear trends across subpopulations by including subpopulation interactions with the linear variable (i.e., gender × linear, school level × linear, and race/ethnicity × linear). We performed all statistical analyses with Stata/IC 12.0 (StataCorp, 2011).
n = 22,783
n = 22,585 % [95% CI]
% [95% CI]
n = 18,854
2009 % [95% CI]
n = 27,228
2000 % [95% CI]
n = 20,556
2002
n = 18,700
n = 22,293 % [95% CI]
n = 22,629 % [95% CI]
% [95% CI]
2009
2006
2004
40.1 [37.5, 42.7] 41.1 [38.3, 43.8] 33.2 [29.7, 36.8] 26.7 [22.8, 30.6] 40.7 [32.0, 49.4] 39.2 [31.0, 47.4]
40.3 [37.6, 43.0] 39.1 [36.5, 41.8] 31.9 [29.5, 34.3] 24.8 [21.0, 28.6] 41.7 [33.8, 49.5] 37.4 [28.0, 46.7]
33.3 [30.6, 36.0] 28.2 [25.8, 30.6] 25.8 [23.1, 28.5] 14.8 [11.9, 17.7] 29.4 [21.9, 36.8] 32.0 [22.4, 41.7]
31.0 [28.1, 33.8] 26.4 [23.8, 29.0] 23.4 [21.1, 25.8] 15.0 [12.1, 18.0] 30.0 [23.4, 36.6] 29.8 [22.8, 36.8]
24.7 [22.6, 26.9] 20.7 [16.7, 24.8] 20.1 [16.8, 23.3] 14.1 [10.1, 18.0] 32.5 [22.4, 42.6] 29.6 [18.8, 40.4]
62.5 [60.3, 64.8] 56.4 [54.0, 58.7] 48.2 [44.6, 51.8] 47.0 [42.9, 51.1] 51.7 [41.0, 62.3] 51.1 [43.4, 58.9]
61.1 [58.8, 63.4] 53.6 [51.1, 56.2] 47.3 [44.5, 50.1] 43.5 [38.3, 48.7] 55.6 [47.6, 63.5] 51.7 [42.2, 61.1]
48.4 [45.6, 51.1] 39.1 [39.6, 41.3] 37.2 [34.6, 39.9] 30.4 [27.0, 33.8] 40.7 [32.8, 48.5] 44.8 [35.8, 53.8]
46.3 [43.4, 49.1] 36.1 [32.9, 39.4] 35.1 [32.0, 38.3] 28.6 [25.6, 31.5] 39.8 [31.7, 47.8] 40.8 [32.0, 49.6]
37.2 [34.5, 39.9] 27.8 [23.3, 32.2] 31.2 [28.8, 33.7] 25.8 [20.5, 31.1] 36.0 [26.8, 45.1] 42.2 [26.4, 57.9]
38.7 [36.3, 41.1] 37.9 [35.1, 40.6] 29.5 [26.9, 32.2] 27.5 [24.7, 30.3] 21.7 [19.0, 24.5] 54.5 [52.2, 56.8] 53.0 [50.4, 55.5] 40.2 [37.7, 42.7] 37.6 [34.9, 40.2] 31.2 [28.8, 33.6] 39.2 [36.8, 41.6] 38.8 [36.3, 41.3] 31.9 [29.6, 34.3] 29.6 [27.2, 32.1] 23.8 [21.3, 26.2] 63.6 [61.4, 65.8] 61.3 [59.1, 63.5] 49.1 [46.6, 51.6] 46.8 [44.0, 49.6] 36.5 [32.8, 40.1]
37.0 [34.8, 39.1] 36.2 [34.0, 38.4] 28.7 [26.6, 30.8] 26.0 [24.0, 28.1] 20.2 [18.1, 22.3] 56.2 [53.9, 58.4] 54.7 [52.7, 56.8] 41.1 [39.0, 43.2] 38.1 [35.9, 40.3] 29.7 [26.8, 32.5] 40.9 [38.5, 43.3] 40.5 [38.2, 42.7] 32.8 [30.3, 35.3] 30.9 [28.4, 33.4] 25.4 [23.2, 27.6] 61.6 [59.6, 63.7] 59.6 [57.6, 61.7] 48.2 [45.6, 50.8] 46.1 [43.7, 48.5] 38.3 [35.8, 40.8]
39.0 [36.8, 41.1] 38.4 [36.3, 40.5] 30.7 [28.6, 32.9] 28.6 [26.5, 30.6] 22.8 [20.8, 24.8] 58.9 [57.0, 61.0] 57.2 [55.3, 59.1] 44.7 [42.5, 46.8] 42.2 [40.1, 44.4] 34.0 [31.8, 36.2]
% [95% CI]
n = 20,543 % [95% CI]
n = 27,214
% [95% CI]
2006
Note. AI/AN = American Indian/Alaska Native; NH = non-Hispanic; NH/PI = Native Hawaiian/Pacific Islander; NYTS = National Youth Tobacco Survey; SHS = secondhand smoke.
Total Gender Male Female Grade level Middle school High school Race/ethnicity NH White NH Black Hispanic NH Asian NH AI/AN NH NH/PId
Characteristic
2004
2002
2000
SHS exposure in rooms
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666 SHS exposure in cars
Table 2. Percentage of Nonsmoking U.S. Adolescents Exposed to SHS in Cars and Rooms on at Least 1 Day in the Past Week: NYTS 2000, 2002, 2004, 2006, and 2009
SHS exposure in cars and in rooms
Nicotine & Tobacco Research (AOR = 0.91, CI = 0.85–0.96, p < .01), and NH Native Hawaiian/ Pacific Islanders (AOR = 0.94, CI = 0.88–0.99, p < .05).
significant downward trends, from 2000 to 2009, of SHS in cars among middle and high school students overall (adjusted odds ratio [AOR] = 0.92, CI = 0.90–0.93, p < .001), and among subpopulations of males (AOR = 0.91, CI = 0.90–0.92, p < .001), females (AOR = 0.92, CI = 0.91–0.93, p < .001), middle school students (AOR = 0.91, CI = 0.90–0.92, p < .001), high school students (AOR = 0.92, CI = 0.91–0.94, p < .001), NH Whites (AOR = 0.92, CI = 0.91–0.94, p < .001), NH Blacks (AOR = 0.89, CI = 0.87–0.91, p < .001), Hispanics (AOR = 0.92, CI = 0.90–0.95, p < .001), NH Asians (AOR = 0.90, CI = 0.87– 0.94, p < .001), and NH American Indian/Native Alaskans (AOR = 0.94, CI = 0.88–0.99, p
Original Investigation
Secondhand Smoke Exposure in Cars and Rooms: Trend Comparisons Among Subpopulations of Nonsmoking U.S. Middle and High School Students Russell K. McIntire PhD, MPH1, Jonathan T. Macy PhD, MPH1, Dong-Chul Seo PhD1, Ashlyn A. Nelson PhD2, Lloyd J. Kolbe PhD1 1Department of Applied Health Science, Indiana University School of Public Health-Bloomington, Bloomington, IN; 2School of Public and Environmental Affairs, Indiana University, Bloomington, IN
Received June 24, 2013; accepted November 18, 2013
Abstract Introduction: Young people in the United States are exposed to secondhand smoke (SHS) primarily in 2 settings: homes and cars. Recently, researchers reported that the prevalence of U.S students exposed to SHS in cars decreased from 2000 to 2009; however, comparisons of trends across school levels, gender, and racial/ethnic groups were not assessed. Moreover, no studies have examined trends of exposure to SHS in rooms. Methods: We used data from the 2000, 2002, 2004, 2006, and 2009 waves of the National Youth Tobacco Survey, a nationally representative cross-sectional survey of U.S. middle and high school students. For SHS in cars and rooms, we identified exposure trends among nonsmokers from 2000 to 2009 and compared trends across subpopulations with binary logistic regression. Results: We identified significant downward linear trends in SHS in cars and rooms for nearly all measured subpopulations of nonsmoking students from 2000 to 2009. SHS exposure in cars and rooms declined at a significantly greater rate for males than for females. SHS exposure in cars declined at a significantly greater rate for non-Hispanic (NH) Blacks than for NH Whites. SHS exposure in rooms declined at a significantly greater rate for NH Whites than for Hispanics and Native Hawaiians/Pacific Islanders. Conclusions: Although prevalence of exposure to SHS in cars and rooms among nonsmoking U.S. middle and high school students has declined from 2000 to 2009, the rates of decline were not equal across genders and racial/ethnic groups. Identification of these differing rates of exposure can help the public health community advocate for interventions focused on reducing adolescent SHS exposure.
Introduction Secondhand smoke (SHS), which is composed of both mainstream smoke exhaled by smokers and sidestream smoke produced by the burning end of tobacco products, is the cause of considerable morbidity and mortality. The U.S. Centers for Disease Control and Prevention (CDC) identified that SHS causes an estimated 49,400 deaths among U.S. nonsmokers per year (CDC, 2008a). U.S. Surgeon Generals’ Reports (U.S. Department of Health and Human Services [DHHS], 2006, 2010) concluded that SHS negatively affects almost every organ in the body and causes lung cancer, heart disease, bronchitis, pneumonia, thrombosis, and sudden infant death syndrome. In the United States, tobacco control efforts such as media campaigns and laws that prohibit smoking in public places have been successful in reducing SHS exposure, but the results have
not been equal for all population groups. For example, SHS exposure in the general population has declined by 70% since 1988, but children have experienced significantly less decline (CDC, 2008b; DHHS, 2006). Studies estimate that more than one in five children in the United States are exposed to SHS each day (DHHS, 2006; McCausland et al., 2005), with higher levels of exposure among younger children compared with older children and among non-Hispanic (NH) Whites and NH Blacks compared with Mexican-American children (Marano, Schober, Brody, & Zhang, 2009). SHS exposure among children occurs primarily in two settings: in the family home and in vehicles (consistent with prior studies, “vehicles” will be referred to as “cars”) (DHHS, 2006; Jarvie & Malone, 2008; Jordan, Price, Dake, & Shah, 2005). While homes and workplaces have been shown to be the predominant location for exposure to SHS, studies have shown
doi:10.1093/ntr/ntt207 Advance Access publication December 24, 2013 © The Author 2013. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: [email protected].
663
Downloaded from http://ntr.oxfordjournals.org/ at University of Wisconsin-Oshkosh on June 10, 2015
Corresponding Author: Jonathan T. Macy, PhD, MPH, Department of Applied Health Science, Indiana University School of Public Health-Bloomington, 1025 East 7th Street, Room 116, Bloomington, IN 47405, USA. Telephone: 812-856-0704; Fax: 812-855-3936; E-mail: [email protected]
SHS exposure in cars and in rooms
664
exposed daily to SHS in rooms, whereas 7% were exposed daily to SHS in cars. Like SHS in cars, we hypothesized that prevalence of SHS in rooms declined for subpopulations from 2000 to 2009 and that there would be no differences in trends of SHS in rooms across genders, school levels, and race/ ethnicities.
Methods Data Source The NYTS measures tobacco-use behaviors, exposure to SHS, smoking cessation, tobacco-related school curriculum, minors’ ability to purchase or obtain tobacco products, attitudes about tobacco, and familiarity with pro- and antitobacco media messages among middle and high school students in the United States (CDC, 2009). To compare trends of SHS exposure among adolescent subpopulations, we used data from five comparable NYTS studies conducted during the springs of 2000, 2002, 2004, 2006, and 2009. We chose not to include data from the 2011 wave of the NYTS because the items for the two main dependent variables were modified for 2011 and are thus not comparable with previous NYTS data. During administrations of the NYTS, participants were asked to complete an anonymous pencil and paper questionnaire in a classroom setting. Participation in all surveys was voluntary at both the school and student level, and no incentives were provided for student participation. Schools used either passive or active permission forms at their discretion to ensure that parents had the option to decline their child’s participation. Prior to data collection, standardized procedures were used to recruit and train data collectors. Sample The NYTS utilized a geographically stratified three-stage cluster sampling design to create nationally representative cross-sectional samples of students attending public and private middle schools (defined as grades 6th, 7th, and 8th) and high schools (defined as grades 9th, 10th, 11th, and 12th) in the 50 states and in Washington, DC (CDC, 2009). Samples were probabilistic and collected without replacement in the following three stages: 1) primary sampling units consisting of counties, groups of small adjacent counties, or a portion of a large county; 2) public or private schools containing eligible grades within Stage 1; and 3) students via whole classrooms within each selected school (CDC, 2009). NYTS data were adjusted for nonresponse and weighted to provide national prevalence estimates for the years of survey administration. The weighting procedure is described in detail elsewhere (CDC, 2004, 2006, 2009). During 2000–2009, small modifications were made in NYTS sampling designs. Despite these modifications, sampling designs enabled comparisons across survey years (Duke et al., 2010; King et al., 2012; CDC, 2010b). The total number of schools that participated in the NYTS data collection waves ranged from 205 in 2009 to 324 in 2000. The total number of students that participated in survey years ranged from 22,679 in 2009 to 35,824 in 2000. The overall response rates for the NYTS surveys ranged from 75% in 2002 to 85% in 2009 (CDC, 2009).
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that the car setting poses a distinct risk for child SHS exposure given the high concentration of smoke that is produced within a car in which passengers are smoking (Ott, Klepeis, & Switzer, 2008; Rees & Connolly, 2006; Semple et al., 2012; Sendzik, Fong, Travers, & Hyland, 2009). While the overwhelming majority of setting-specific SHS interventions focus on the home as the exposure site, media and educational campaigns have been launched at national (American Legacy Foundation, 2005, January 11) and state (Americans for Nonsmokers’ Rights [ANR], 2013, August 28) levels to encourage parents to make not just their homes but also their cars smoke-free. In addition, U.S. states and jurisdictions have enacted legislation to protect children from SHS in cars. In April 2006, Arkansas became the first state to pass a law making smoking in private cars carrying children a punishable offense (CDC, 2012). Shortly thereafter in 2006, Louisiana passed a similar law, followed by California in 2008, and Maine in 2009 (CDC, 2012). Most recently, Utah and Oregon passed laws banning smoking in vehicles in the presence of children effective May 2013 and January 2014, respectively (ANR, 2013, July 26). Although smoke-filled cars have been identified as highrisk environments for children, only a few studies have analyzed the frequency of SHS in cars among nationally representative samples of U.S. children (King, Dube, & Tynan, 2012; McCausland et al., 2005). One study (McCausland et al., 2005) found the prevalence of daily exposure to SHS in cars among U.S middle and high school students declined 37% between 1999 and 2003. The study reported that in 2003, 7% of middle and high school students were exposed daily to SHS in cars. Using data from the National Youth Tobacco Survey (NYTS), King et al. (2012) showed that the prevalence of U.S adolescent SHS in cars decreased from 2000 to 2009 among all demographic subpopulations of smoking and nonsmoking school students. Despite these downward trends, in 2009, over one fifth of nonsmoking middle and high school students were exposed to SHS in cars at least once in the past week. While King et al. (2012) identified reductions in prevalence of SHS in cars among all measured adolescent demographic subpopulations from 2000 to 2009, they did not test whether there were significant differences in trends of adolescent SHS in cars across these subpopulations. This information would be helpful to determine if any of these subpopulations might warrant particular attention as part of SHS-reduction strategies. Therefore, in this study, we used NYTS data to identify the prevalence and trends of SHS in cars among demographic subpopulations of nonsmoking U.S. school students from 2000 to 2009 and then tested whether there were significant differences in trends across genders, school levels, and race/ethnicities. Since public health interventions at the national level have not focused on reducing SHS in cars among specific demographic subpopulations of U.S. adolescents, we hypothesized that there would be no differences in SHS in cars trends from 2000 to 2009 across genders, school levels, and race/ethnicities. Finally, we also explored the prevalence and trends of adolescent exposure to SHS in rooms. Although studies have identified recent increases in workplace smoking bans and voluntary home smoking rules, millions are still exposed to SHS in these locations (DHHS, 2006; King, Dube, & Homa, 2013). Like SHS in cars, few studies have focused on SHS in rooms, and even fewer have explored both SHS in cars and SHS in rooms. A notable exception is the McCausland et al. (2005) study that reported that 13% of U.S. adolescents were
Nicotine & Tobacco Research female), and race/ethnicity (NH White, NH Black, Hispanic, NH Asian, NH American Indian/Alaskan Native, NH Native Hawaiian/Pacific Islander). We dichotomized the grade variable into a school level variable reflecting middle school (6th, 7th, and 8th grades) or high school (9th, 10th, 11th, and 12th grades). We coded all participants reporting “ungraded or no grade” as missing.
Our analyses included only those students who self-identified as nonsmokers. Nonsmokers were defined as participants who answered “0 days” to the following question: “During the past 30 days, on how many days did you smoke cigarettes?” Of the 139,627 participants contained in the five datasets, 114,200 (84.7%) were nonsmokers. Of the nonsmokers, the percent of respondents excluded due to missing data for the dependent variables (SHS in cars and SHS in rooms) from the survey years ranged from 0.9% to 3.8% for SHS in cars and 1.9% to 3.7% for SHS in rooms. The resulting sample sizes for the survey years are found in Table 1. Demographic characteristics of the cross-sectional samples, shown in Table 1, were similar across all of the survey administrations.
Statistical Analyses
Measures SHS in Cars and Rooms The NYTS assessed SHS in cars and SHS in rooms, respectively, using the following two items: “During the past 7 days, on how many days did you ride in a car with someone who was smoking cigarettes?” and “During the past 7 days, on how many days were you in the same room with someone who was smoking cigarettes?” Responses to these items were amalgamated by CDC on an ordinal scale indicating increasing frequency of exposure: “0 days,” “1 or 2 days,” “3 or 4 days,” “5 or 6 days,” or “7 days.” For both the SHS in cars and SHS in rooms variables, we treated participants as exposed if they reported exposure on at least one of the past 7 days. Linear Trend Variable In order to account for the nonconsecutive variations between survey years, the CDC used orthogonal polynomials to create coefficients representing each year of survey administration to aid in the trend analysis (King et al., 2012). We used these coefficients to create the continuous linear variable in order to identify and compare trends.
Results Prevalence and Trend Analyses Table 2 shows the prevalence of SHS in cars for the total population and all measured subpopulations of nonsmoking middle and high school students for all NYTS administrations. In 2000, 39.0% of middle and high school students were exposed to SHS in cars, whereas in 2009, 22.8% of students were exposed to SHS in cars. Logistic regression analyses identified
Demographics NYTS participants reported their age, grade (6th, 7th, 8th, 9th, 10th, 11th, 12th, ungraded, or no grade), gender (male or
Table 1. Demographic Characteristics of Cross-Sectional Samples: NYTS 2000, 2002, 2004, 2006, and 2009
Variable Gender Male Female Grade level Middle High Race/ethnicity NH White NH Black Hispanic NH Asian NH AI/AN NH NH/PI
2000
2002
2004
2006
2009
Total
n (%)
n (%)
n (%)
n (%)
n (%)
n (%)
13,771 (49.5) 14,048 (50.5)
10,430 (48.91) 10,894 (51.09)
11,204 (48.83) 11,741 (51.17)
10,802 (47.75) 11,818 (52.25)
9,274 (48.51) 9,842 (51.49)
55,481 (48.74) 58,343 (51.26)
14,025 (50.48) 13,757 (49.52)
10,971 (51.51) 10,326 (48.49)
12,314 (53.56) 10,678 (46.44)
11,188 (49.28) 11,516 (50.72)
9,380 (49.09) 9,727 (50.91)
57,878 (50.82) 56,004 (49.18)
14,675 (53.33) 4,688 (17.04) 5,984 (21.74) 1,400 (5.09) 451 (1.64) 321 (1.17)
10,078 (47.59) 4,214 (19.90) 5,240 (24.74) 1,129 (5.33) 286 (1.35) 229 (1.08)
10,353 (46.56) 4,443 (19.98) 5,852 (26.32) 1,166 (5.24) 264 (1.19) 158 (0.71)
9,720 (43.81) 4,663 (21.02) 6,007 (27.08) 1,307 (5.89) 243 (1.10) 245 (1.10)
9,100 (49.01) 3,157 (17.00) 5,196 (27.99) 800 (4.31) 207 (1.11) 107 (0.58)
53,926 (48.28) 21,165 (18.95) 28,279 (25.32) 5,802 (5.20) 1,451 (1.30) 1,060 (0.95)
Note. AI/AN = American Indian/Alaska Native; NH = non-Hispanic; NH/PI = Native Hawaiian/Pacific Islander; NYTS = National Youth Tobacco Survey.
665
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We used sampling information (survey weights, strata, and primary sampling units) provided by the NYTS methodology reports to adjust for the complex survey design and to produce population estimates for SHS in cars and SHS in rooms for each measured year from 2000 to 2009 (CDC, 2009). We generated descriptive statistics to identify prevalence estimates of SHS in cars and SHS in rooms with 95% CIs in each survey year. We then determined linear trends by interpreting the coefficient of the linear variable in binary logistic regression models. All logistic regression models controlled for gender, school level, and race/ethnicity in order to account for changes in these variables across survey years. To compare linear trends of SHS in cars and SHS in rooms across subpopulations, we generated two binary logistic regression models, one for SHS in cars and one for SHS in rooms. We compared linear trends across subpopulations by including subpopulation interactions with the linear variable (i.e., gender × linear, school level × linear, and race/ethnicity × linear). We performed all statistical analyses with Stata/IC 12.0 (StataCorp, 2011).
n = 22,783
n = 22,585 % [95% CI]
% [95% CI]
n = 18,854
2009 % [95% CI]
n = 27,228
2000 % [95% CI]
n = 20,556
2002
n = 18,700
n = 22,293 % [95% CI]
n = 22,629 % [95% CI]
% [95% CI]
2009
2006
2004
40.1 [37.5, 42.7] 41.1 [38.3, 43.8] 33.2 [29.7, 36.8] 26.7 [22.8, 30.6] 40.7 [32.0, 49.4] 39.2 [31.0, 47.4]
40.3 [37.6, 43.0] 39.1 [36.5, 41.8] 31.9 [29.5, 34.3] 24.8 [21.0, 28.6] 41.7 [33.8, 49.5] 37.4 [28.0, 46.7]
33.3 [30.6, 36.0] 28.2 [25.8, 30.6] 25.8 [23.1, 28.5] 14.8 [11.9, 17.7] 29.4 [21.9, 36.8] 32.0 [22.4, 41.7]
31.0 [28.1, 33.8] 26.4 [23.8, 29.0] 23.4 [21.1, 25.8] 15.0 [12.1, 18.0] 30.0 [23.4, 36.6] 29.8 [22.8, 36.8]
24.7 [22.6, 26.9] 20.7 [16.7, 24.8] 20.1 [16.8, 23.3] 14.1 [10.1, 18.0] 32.5 [22.4, 42.6] 29.6 [18.8, 40.4]
62.5 [60.3, 64.8] 56.4 [54.0, 58.7] 48.2 [44.6, 51.8] 47.0 [42.9, 51.1] 51.7 [41.0, 62.3] 51.1 [43.4, 58.9]
61.1 [58.8, 63.4] 53.6 [51.1, 56.2] 47.3 [44.5, 50.1] 43.5 [38.3, 48.7] 55.6 [47.6, 63.5] 51.7 [42.2, 61.1]
48.4 [45.6, 51.1] 39.1 [39.6, 41.3] 37.2 [34.6, 39.9] 30.4 [27.0, 33.8] 40.7 [32.8, 48.5] 44.8 [35.8, 53.8]
46.3 [43.4, 49.1] 36.1 [32.9, 39.4] 35.1 [32.0, 38.3] 28.6 [25.6, 31.5] 39.8 [31.7, 47.8] 40.8 [32.0, 49.6]
37.2 [34.5, 39.9] 27.8 [23.3, 32.2] 31.2 [28.8, 33.7] 25.8 [20.5, 31.1] 36.0 [26.8, 45.1] 42.2 [26.4, 57.9]
38.7 [36.3, 41.1] 37.9 [35.1, 40.6] 29.5 [26.9, 32.2] 27.5 [24.7, 30.3] 21.7 [19.0, 24.5] 54.5 [52.2, 56.8] 53.0 [50.4, 55.5] 40.2 [37.7, 42.7] 37.6 [34.9, 40.2] 31.2 [28.8, 33.6] 39.2 [36.8, 41.6] 38.8 [36.3, 41.3] 31.9 [29.6, 34.3] 29.6 [27.2, 32.1] 23.8 [21.3, 26.2] 63.6 [61.4, 65.8] 61.3 [59.1, 63.5] 49.1 [46.6, 51.6] 46.8 [44.0, 49.6] 36.5 [32.8, 40.1]
37.0 [34.8, 39.1] 36.2 [34.0, 38.4] 28.7 [26.6, 30.8] 26.0 [24.0, 28.1] 20.2 [18.1, 22.3] 56.2 [53.9, 58.4] 54.7 [52.7, 56.8] 41.1 [39.0, 43.2] 38.1 [35.9, 40.3] 29.7 [26.8, 32.5] 40.9 [38.5, 43.3] 40.5 [38.2, 42.7] 32.8 [30.3, 35.3] 30.9 [28.4, 33.4] 25.4 [23.2, 27.6] 61.6 [59.6, 63.7] 59.6 [57.6, 61.7] 48.2 [45.6, 50.8] 46.1 [43.7, 48.5] 38.3 [35.8, 40.8]
39.0 [36.8, 41.1] 38.4 [36.3, 40.5] 30.7 [28.6, 32.9] 28.6 [26.5, 30.6] 22.8 [20.8, 24.8] 58.9 [57.0, 61.0] 57.2 [55.3, 59.1] 44.7 [42.5, 46.8] 42.2 [40.1, 44.4] 34.0 [31.8, 36.2]
% [95% CI]
n = 20,543 % [95% CI]
n = 27,214
% [95% CI]
2006
Note. AI/AN = American Indian/Alaska Native; NH = non-Hispanic; NH/PI = Native Hawaiian/Pacific Islander; NYTS = National Youth Tobacco Survey; SHS = secondhand smoke.
Total Gender Male Female Grade level Middle school High school Race/ethnicity NH White NH Black Hispanic NH Asian NH AI/AN NH NH/PId
Characteristic
2004
2002
2000
SHS exposure in rooms
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666 SHS exposure in cars
Table 2. Percentage of Nonsmoking U.S. Adolescents Exposed to SHS in Cars and Rooms on at Least 1 Day in the Past Week: NYTS 2000, 2002, 2004, 2006, and 2009
SHS exposure in cars and in rooms
Nicotine & Tobacco Research (AOR = 0.91, CI = 0.85–0.96, p < .01), and NH Native Hawaiian/ Pacific Islanders (AOR = 0.94, CI = 0.88–0.99, p < .05).
significant downward trends, from 2000 to 2009, of SHS in cars among middle and high school students overall (adjusted odds ratio [AOR] = 0.92, CI = 0.90–0.93, p < .001), and among subpopulations of males (AOR = 0.91, CI = 0.90–0.92, p < .001), females (AOR = 0.92, CI = 0.91–0.93, p < .001), middle school students (AOR = 0.91, CI = 0.90–0.92, p < .001), high school students (AOR = 0.92, CI = 0.91–0.94, p < .001), NH Whites (AOR = 0.92, CI = 0.91–0.94, p < .001), NH Blacks (AOR = 0.89, CI = 0.87–0.91, p < .001), Hispanics (AOR = 0.92, CI = 0.90–0.95, p < .001), NH Asians (AOR = 0.90, CI = 0.87– 0.94, p < .001), and NH American Indian/Native Alaskans (AOR = 0.94, CI = 0.88–0.99, p
