Saliva cotinine as an indicator of cigarette smoking in adolescents

Examining the Validity of Self-reported Primary and Secondary Exposure to Cigarette Smoke in Adolescent Girls: The Utility of Salivary Cotinine as a Biomarker

BACKGROUND

Studies of cigarette use and exposure often rely on either self-report or cotinine assay. In adolescence it is not clear how well assays and self-report correspond, or what effect estrogen exposure has on cotinine.

OBJECTIVES

This study sought to identify optimal cut-points for salivary cotinine thresholds for girls with primary, secondary, and no smoke exposure, and whether menarche and hormone contraceptive use are important for interpreting salivary cotinine.

METHODS

This longitudinal prospective study recruited 262 healthy adolescent girls who participated in three annual interviews across 24 months. Salivary cotinine assays and self-report of primary and secondary smoke exposure, menarcheal status, and hormone contraceptive use were collected.

RESULTS

No adolescents reported primary smoke exposure without secondary exposure. Optimal cut-points for distinguishing primary smoke exposure from secondary-only and no smoke exposure were 1.05 and 3.01 ng/ml, respectively based on receiver operator curves (ROC); no reliable cut-point for secondary-only versus no smoke exposure was identified. The ideal salivary cotinine cut-point to distinguish primary smoke exposure varied by hormone contraceptive use and was 2.14 ng/ml for those using progesterone contraceptives, higher than that of girls using estrogen contraceptives and those not using hormone contraceptives.

CONCLUSIONS

This study is the first to examine variance in salivary cotinine cut-points based on hormone exposure for adolescent girls, with findings indicating that hormone contraceptive use in particular may be a key consideration when identifying adolescent smoking. The use of previously recommended salivary cotinine cut-points of 3.85 ng/ml or higher may overestimate nonsmokers.

Heterogeneity in Smokers' Responses to Tobacco Control Policies

This paper uses unconditional quantile regression to estimate whether smokers' responses to tobacco control policies change across the distribution of smoking levels. I measure smoking behavior with the number of cigarettes smoked per day and also with serum cotinine levels, a continuous biomarker of nicotine exposure, using individual-level repeated cross-section data from the National Health and Nutrition Examination Surveys. I find that the cigarette taxes lead to reductions in both the number of cigarettes smoked per day and in smokers' cotinine levels. These reductions are most pronounced in the middle quantiles of both distributions in terms of marginal effects, but most pronounced in the lower quantiles in terms of tax elasticities. I do not find that higher cigarette taxes lead to statistically significant changes in the amount of nicotine smokers ingest from each cigarette. Copyright © 2015 John Wiley & Sons, Ltd.

The influence of parental smoking and family type on saliva cotinine in UK ethnic minority children: a cross sectional study

BACKGROUND

In the United Kingdom, there has been an increase in cigarette smoking in ethnic minority adults since the 1970s; in some groups levels are now similar to that of White British people. We aimed to examine the determinants of exposure to secondhand smoke in ethnic minority children. We hypothesised that exposure to secondhand smoke in children will vary across ethnic groups, but that the correlates of exposure would be similar to that of Whites.

METHODS

The Determinants of Adolescent Social well-being and Health sample comprises 3468 White United Kingdom and ethnic minority (Black Caribbean, Black African, Indian, Pakistani, Bangladeshi) pupils aged 11-13 yrs. Outcome was saliva cotinine concentration. Explanatory variables collected by self-complete questionnaire included ethnicity, child reported household smoking and socio-economic circumstances. Data were analysed using linear regression models with a random intercept function.

RESULTS

Ethnic minority children had lower saliva cotinine than Whites, partly explained by less smoking among parents. White and Black Caribbean children had higher cotinine levels if they lived in a household with a maternal smoker only, than with a paternal smoker only. Living in a lone compared to a dual parent household was associated with increased cotinine concentration of 45% (95%CI 5, 99%) in Whites, 27% (95%CI 5,53%) in Black Caribbeans and 21% (95%CI 1, 45%) in Black Africans after adjusting for household smoking status. Material disadvantage was a significant correlate only for White children (40% (95%CI 1, 94%) increase in cotinine in least compared to most advantaged group).

CONCLUSIONS

Ethnic minority children were less exposed to secondhand smoke than Whites, but the variations within groups were similarly patterned. These findings suggest that it is important not to be complacent about low smoking prevalence in some minority groups.

Agreement between self-reported smoking and cotinine concentration in adolescents: a validation study in Brazil

PURPOSE

To validate self-reported data on smoking in adolescents in comparison with cotinine concentration.

METHODS

Two thousand two hundred nine seventh- and eighth-grade students from 32 public schools in Pelotas, Brazil. Adolescents were contacted twice--before and after an educational intervention--and samples of urine for cotinine analyses were taken. In this paper, only data from the baseline phase are presented. High-performance liquid chromatography was used for cotinine analysis. Two cutoff points for cotinine were used: 10 ng/mL and 30 ng/mL. Two self-reported smoking variables were used: at least one cigarette smoked in the previous 30 days; and daily smoking.

RESULTS

The self-reported prevalence of smoking in the previous 30 days was 7.4%, and 0.9% of the adolescents reported to be daily smokers. Those who reported smoking in the previous 30 days presented mean cotinine values 10 times greater than those who reported to be nonsmokers. Using a cutoff of 10 ng/mL for cotinine, sensitivity of self-reported smoking was 16.3% (95% confidence interval [CI] 11.7; 20.9) and specificity was 93.6% (95% CI 92.8; 95.0). Using a cutoff of 30 ng/mL, sensitivity was 22.6% (95% CI 15.6; 29.6) and specificity was 93.7% (95% CI 92.6; 94.8).

CONCLUSIONS

Self-reported smoking presents low agreement with cotinine concentration, suggesting that adolescents underestimate tobacco consumption.

Assessing smoking status in children, adolescents and adults: cotinine cut-points revisited

AIMS

To reassess saliva cotinine cut-points to discriminate smoking status. Cotinine cut-points that are in use were derived from relatively small samples of smokers and non-smokers 20 or more years ago. It is possible that optimal cut-points may have changed as prevalence and exposure to passive smoking have declined.

DESIGN

Cross-sectional survey of the general population, with assessment of self-reported smoking and saliva cotinine.

PARTICIPANTS

A total of 58 791 respondents aged 4 years and older in the Health Survey for England for the years 1996-2004 who provided valid saliva cotinine specimens.

MEASURES

Saliva cotinine concentrations, demographic variables, self-reported smoking, presence or absence of smoking in the home, a composite index of social disadvantage derived from occupation, housing tenure and access to a car.

FINDINGS

A cut-point of 12 ng/ml performed best overall, with specificity of 96.9% and sensitivity of 96.7% in discriminating confirmed cigarette smokers from never regular smokers. This cut-point also identified correctly 95.8% of children aged 8-15 years smoking six or more cigarettes a week. There was evidence of substantial misreport in claimed ex-smokers, especially adolescents (specificity 72.3%) and young adults aged 16-24 years (77.5%). Optimal cut-points varied by presence (18 ng/ml) or absence (5 ng/ml) of smoking in the home, and there was a gradient from 8 ng/ml to 18 ng/ml with increasing social disadvantage.

CONCLUSIONS

The extent of non-smokers' exposure to other people's tobacco smoke is the principal factor driving optimal cotinine cut-points. A cut-point of 12 ng/ml can be recommended for general use across the whole age range, although different cut-points may be appropriate for population subgroups and in societies with differing levels of exposure to secondhand smoke.

Smoking status of step-parents as a risk factor for smoking in adolescence

AIM

To examine the extent to which smoking by step-parents and biological parents predicts adolescent smoking. DESIGN Five-year cohort study. SETTING Thirty-six schools in South London, England. Participants A subset of 650 students participating in the Health and Behaviour In Teenagers Study (HABITS), who reported living in step-families, were assessed annually from age 11-12 to age 15-16 years.

MEASUREMENTS

Students reported their smoking status, which was cotinine-verified, as well as whether their parents smoked and, if they lived with a step-parent, whether that step-parent smoked. Analyses also controlled for gender, ethnicity and deprivation.

FINDINGS

Students who reported that just their step-parent smoked at age 11-12 were significantly more likely to report current smoking at any time-point from age 11-16 than those who reported having neither biological parents nor a step-parent who smoked [odds ratio (OR) 2.72, 95% confidence interval (CI) = 1.36-5.47], as were those with both a parent and a step-parent who smoked (OR 2.23, 95% CI = 1.46-3.41). While the association between smoking in students and smoking in biological parents in this subsample did not reach statistical significance (OR 1.39, 95% CI = 0.88-2.19), these students were no more or less likely to smoke than those with just a step-parent who smoked.

CONCLUSION

Smoking by a non-biological parent appears at least as influential as smoking by biological parents. This confirms the importance of social influence on smoking initiation and suggests that attempts to work with parents in smoking prevention should involve, and perhaps pay particular attention to, step-parents who smoke.

Persistent impact of pubertal timing on trends in smoking, food choice, activity, and stress in adolescence

OBJECTIVES

a) To replicate the established association between early puberty and smoking; b) to see whether differences between early and late maturers narrowed with increasing age and differed by gender; and c) to determine whether other health behaviors (food choice, physical activity, sedentary behavior) and stress showed the same association with pubertal timing.

METHODS

The Health and Behaviour in Teenagers Study (HABITS) followed a cohort of 5863 adolescents from ages 11 to 12 years (UK year 7; US grade 6) for 5 years. Puberty was assessed with the Pubertal Development Scale. Three pubertal timing groups were created by identifying adolescents who reached midpuberty relatively early, average, or late, compared with their peers. Longitudinal trends in health behaviors and stress were compared between the three groups.

RESULTS

Smoking rates were higher throughout adolescence among early-maturing students, with no evidence that late-maturers "caught up" when they reached puberty, although group differences narrowed over time. Early-maturing students had higher rates of sedentary behaviors but also reported higher rates of vigorous activity than their "on-time" developing counterparts. Patterns in dietary behaviors and stress showed lower rates of daily breakfast and higher stress among early-maturing girls, but not boys. Overall, the effects were largest in early adolescence (ages 11-13 years) and became smaller at older ages (ages 14-16 years).

CONCLUSION

Early-maturing adolescents are at increased risk for unhealthy behaviors, especially smoking, and although differences attenuate during adolescence, they remain significant at age 16 years. This suggests that early maturation may be a cause of, or is at least a marker for, differences in lifestyle.

Does smoking in adolescence affect body mass index, waist or height? Findings from a longitudinal study

AIM

To assess the effect of smoking uptake on body mass index (BMI), waist circumference and height during adolescence.

DESIGN

Five-year longitudinal study.

SETTING

Thirty-six schools in South London, England, selected by a stratified random sampling procedure designed to ensure ethnic and socio-economic diversity.

PARTICIPANTS

A total of 5863 students took part in the HABITS (Health and Behaviour in Teenagers) Study between 1999 and 2003.

MEASUREMENTS

Self-reported smoking behaviour, saliva cotinine concentrations and measured weight, waist circumference and height were obtained, along with information on gender, ethnicity, socio-economic deprivation, pubertal status, self-reported exercise and dieting. Students were examined annually from school year 7 (ages 11-12) to year 11 (ages 15-16), with response rates ranging from 74 to 84%. A total of 2665 never smokers at year 7 with complete data for years 7 and 11 were included in the analyses.

FINDINGS

Adjusting for year 7 BMI and other potential confounders, regular smokers (more than six cigarettes a week) at year 11 had significantly lower BMI (P = 0.002) than other students. Smokers defined by a cotinine above 15 ng/ml also had lower BMI (P < 0.0001). Waist circumferences were lower in regular smokers (P = 0.014) and cotinine-defined smokers (P < 0.011). No consistent association was found between smoking and height. The adjusted difference in weight between regular smokers and other students amounted to 1.8 kg (95% CI, 0.52-3.17) for an average-height student.

CONCLUSION

Taking up regular smoking during adolescence may result in a lower BMI, but the effect is small and of uncertain significance.

Interpretation of oral fluid tests for drugs of abuse

Oral fluid testing for drugs of abuse offers significant advantages over urine as a test matrix. Collection can be performed under direct observation with reduced risk of adulteration and substitution. Drugs generally appear in oral fluid by passive diffusion from blood, but also may be deposited in the oral cavity during oral, smoked, and intranasal administration. Drug metabolites also can be detected in oral fluid. Unlike urine testing, there may be a close correspondence between drug and metabolite concentrations in oral fluid and in blood. Interpretation of oral fluid results for drugs of abuse should be an iterative process whereby one considers the test results in the context of program requirements and a broad scientific knowledge of the many factors involved in determining test outcome. This review delineates many of the chemical and metabolic processes involved in the disposition of drugs and metabolites in oral fluid that are important to the appropriate interpretation of oral fluid tests. Chemical, metabolic, kinetic, and analytic parameters are summarized for selected drugs of abuse, and general guidelines are offered for understanding the significance of oral fluid tests.

Carbon in airway macrophages and lung function in children

BACKGROUND

Epidemiologic studies indirectly suggest that the inhalation of carbonaceous particulate matter impairs lung function in children. Using the carbon content of airway macrophages as a marker of individual exposure to particulate matter derived from fossil fuel, we sought direct evidence of this association.

METHODS

Airway macrophages were obtained from healthy children through sputum induction, and the area of airway macrophages occupied by carbon was measured. Lung function was measured with the use of spirometry. We modeled the exposure to primary particulate matter (PM) that is less than 10 mum in aerodynamic diameter (PM10) at or near each child's home address. Linear regression was used to evaluate associations between carbon content of alveolar macrophages and variables that may affect individual exposure. To determine whether lung function that is reduced for other reasons is associated with an increase in the carbon content of airway macrophages, we also studied children with severe asthma.

RESULTS

We were able to assess the carbon content of airway macrophages in 64 of 114 healthy children (56 percent). Each increase in primary PM10 of 1.0 microg per cubic meter was associated with an increase of 0.10 microm2 (95 percent confidence interval, 0.01 to 0.18) in the carbon content of airway macrophages, and each increase of 1.0 microm2 in carbon content was associated with a reduction of 17 percent (95 percent confidence interval, 5.6 to 28.4 percent) in forced expiratory volume in one second, of 12.9 percent (95 percent confidence interval, 0.9 to 24.8 percent) in forced vital capacity, and of 34.7 percent (95 percent confidence interval, 11.3 to 58.1 percent) in the forced expiratory flow between 25 and 75 percent of the forced vital capacity. The carbon content of airway macrophages was lower in children with asthma than in healthy children.

CONCLUSIONS

There is a dose-dependent inverse association between the carbon content of airway macrophages and lung function in children. We found no evidence that reduced lung function itself causes an increase in carbon content.

Substance use among school-based youths in northern Mexico

A small base of research suggests that adolescent substance use is a growing public health concern in Mexico. Employing confidential methods, the International Longitudinal Survey of Adolescent Health was administered to assess substance use among 1,238 students in northern Mexico. A large proportion of students indicated lifetime use of tobacco and alcohol. Gender differences in tobacco, alcohol, and marijuana were also evident. The current findings are congruent with the sparse extant data on youths' substance use in Mexico and highlight the need for early prevention interventions.

CYP2A6, MAOA, DBH, DRD4, and 5HT2A genotypes, smoking behaviour and cotinine levels in 1518 UK adolescents

OBJECTIVES

Smoking is a major cause of death and often initiates in adolescence. Mutations in CYP2A6 slow metabolism of nicotine to cotinine. Haploinsufficiency in adults is associated with lower cigarette consumption, lower cotinine level and higher quit rates. Other genes are also implicated in smoking behaviour. We explored smoking behaviour and cotinine levels in relation to genotypes in adolescents.

METHODS

1518 subjects from the Ten Towns Heart Health Study were genotyped for CYP2A6 alleles *1A, *1B, *2, *4, *5, *9 and *12 to classify predicted nicotine metabolism rate. DBH(rs77905), MAOA(rs1801291+VNTR), DRD4(VNTR) and 5HT2A(rs6313) were also studied. Smoking status was established by questionnaire and salivary cotinine measurement at 13-15 and 18 years.

RESULTS

No significant associations were identified for DBH, MAOA, DRD4 and 5HT2A markers, with smoking status or cotinine level at either age. At age 18, haploinsufficiency (HI) for CYP2A6 was associated with a higher odds of being a current smoker compared with the *1B carriers (WT1B) (OR = 2.23 (1.16, 4.27) for current versus ex); *1A homozygotes (WT1A) were also at slightly higher risk (OR = 1.44 (1.01, 2.06)). Partial haploinsufficiency (PHI) was not associated with being a current smoker. There were no significant associations at age 13-15. PHI and HI were associated with higher cotinine levels amongst smokers at both 13-15 and at 18 years compared with WT1B and WT1A groups.

CONCLUSIONS

CYP2A6 haploinsufficiency increases likelihood of continuing smoking in teenagers. We hypothesize an explanatory 'occupancy' model to explain why haploinsufficiency results in faster progression to nicotine dependence, but lower subsequent consumption.

Accuracy of parental and youth reporting of secondhand smoke exposure: the Florida youth cohort study

The accuracy of adolescent and parental reports of youth secondhand smoke exposure has received limited attention in the research literature. Florida Youth Cohort Study participants provided saliva samples during the fifth round of interviews for determination of cotinine levels. After exclusion of admitted or likely youth smokers with cotinine levels>14.7 ng/ml, there were 341 youth ages 13-17 who completed a telephone interview; 304 parents of these participants completed a similar secondhand smoke exposure interview. Adolescents with cotinine levels above the threshold of detection (> 0.10 ng/ml) were considered exposed. Specificity ranged from 87.1-97.8. Positive predictive value, negative predictive value, sensitivity, and kappa values varied considerably by the reporting source (e.g., youth, parent, or a combination of responses), and the age and gender of the youth respondent. Agreement between youth and parent that at least one parent smoked inside the home yielded the best combination of sensitivity (85.0) and specificity (89.8) and was least affected by the age and gender of the youth respondent.

Short term patterns of early smoking acquisition

OBJECTIVE

To describe short term patterns of smoking acquisition exhibited by adolescent smokers.

DESIGN

Interview records from the prospective development and assessment of nicotine dependence in youth study were examined retrospectively. Interviews were conducted three times per year over 30 months.

SUBJECTS

164 students in grades 7-9 (ages 12-15 years, 86 girls, 78 boys) who had used cigarettes at least twice.

MAIN OUTCOME MEASURES

A continuous timeline of smoking activity, beginning with the subject's first use of tobacco and continuing through follow up, was translated into six patterns--abstinent, sporadic, occasional, daily, escalating, and intermittent. Outcome measures were the proportion of subjects starting/ending in each pattern, and the number of transitions per subject between patterns.

RESULTS

There was a general but discontinuous progression from infrequent to more frequent use, with many interspersed periods of not smoking. Escalation to daily smoking was common after the development of dependence symptoms, but was rare among those who did not have symptoms. After the appearance of symptoms, both transitions to heavier daily smoking and attempts at cessation increased.

CONCLUSIONS

Movement to heavier, more frequent smoking is generally unidirectional, although many youths attempt to quit one or more times. The appearance of any symptom of dependence altered the subsequent pattern of smoking behaviour. Future investigators might consider using more frequent data points and a continuous timeline to track smoking behaviour.

Tobacco dependence in the general population in Italy

BACKGROUND

Measures of tobacco dependence are mainly used in the clinical setting, but limited information is available on tobacco dependence on a population level.

MATERIALS AND METHODS

To obtain estimates of tobacco dependence on a population level, a six-item Fagerstrom questionnaire was used in two surveys, conducted in 2002-2003 on a sample of 6773 individuals aged 15 years or over, representative of the Italian adult population.

RESULTS

Overall, 27.1% of Italian adults described themselves as current cigarette smokers (32.2% of men, 22.4% of women). Of all smokers, 42.8% were classified as very low dependent, 28.6% as low dependent, 11.0% as intermediate, 13.8% as high and only 3.8% as very high dependent. The proportions of very low/low dependent were 67.4% in men and 76.8% in women. Those of high/very high dependent smokers were 21.4% in men and 12.5% in women, but only 2.8% at age 15-17 years and 8.4% at age 18-24 years. Only 23% of smokers, moreover, found it difficult to avoid smoking in places where smoking was forbidden.

CONCLUSIONS

The observation that over two-thirds of smokers on a population level in Italy report low or very low dependence has useful implication for intervention on stopping smoking, particularly in the young, who appear to be low dependent. However, in this age group cessation rates were comparatively low.

A sensitization–homeostasis model of nicotine craving, withdrawal, and tolerance: Integrating the clinical and basic science literature

Recent reports suggest that nicotine withdrawal symptoms are common among adolescents after a few weeks of intermittent tobacco use. No current model of nicotine dependence had predicted the rapid development of symptoms of dependence and withdrawal before the development of tolerance. We present a model that integrates neuroscience with clinical observations regarding how nicotine dependence develops, progresses, and resolves in humans. The central tenet of this sensitization-homeostasis model is that nicotine's dependence liability derives from its ability to stimulate neural pathways responsible for the suppression of craving. As a result of sensitization, the craving suppression produced by nicotine is magnified to superphysiological levels. The overinhibition of neurons responsible for craving initiates compensatory homeostatic measures that stimulate the craving pathways and result in craving when nicotine is absent. Separate homeostatic mechanisms are responsible for craving, withdrawal, and tolerance. The sensitization-homeostasis model is unique in its attribution of dependence to craving suppression, its attention to the temporal relationships among clinical features of nicotine dependence, and its extensive integration of clinical observations and basic science. It provides a framework for theory-based research.

Substance use among school-based youths in Puerto Rico: differences between gender and grade levels

The present study examined substance use rates among adolescents in Grades 7-12 in Puerto Rico. Nine hundred eighty-nine students completed the Spanish version of the International Survey of Adolescent Health. More than 50% of middle school youths and 75% of high-school youths reported lifetime alcohol use. Female gender was associated with tobacco use in middle school while male gender was associated with marijuana use in high school. High-school females reported lower rates of tobacco use and marijuana use than middle-school females. High-school males exhibited substantially higher drug-use rates than middle-school males for each substance. These findings may suggest that universal drug prevention interventions may be needed for females in Puerto Rico before they enter middle school, while targeted interventions aimed at high-risk females who continue to smoke tobacco or marijuana may be more effective during high school. In contrast, targeted drug prevention interventions for males probably need to begin in middle school and be maintained if not increased in intensity throughout the high-school years.

Development of lung function in early life: influence of birth weight in infants of nonsmokers

This study aimed to compare lung growth and development during the first year of life in healthy term infants of low or appropriate birth weight for gestation. Paired measurements of forced expiratory volume in 0.4 second, FVC, and forced expiratory flow when 75% of FVC has been exhaled were obtained, using the raised volume technique, at about 7 weeks and 9 months of age in 80 infants (32 low and 48 appropriate birth weight for gestation) of white, nonsmoking mothers. Forced flows and volumes increased with growth. Longitudinal trends in results were compared between the two groups, using random effects modeling and adjusted for potential confounding factors. After adjustment for sex, age, and length, forced expiratory volume was significantly reduced by an average (95% confidence interval) of 9% (2 to 16%) in low birth weight compared with appropriate birth weight for gestation infants throughout the first year of life, with a similar trend in forced expiratory flow (8% [-2 to 17%]) and FVC (4% [-3 to 11%]). These findings suggest that lung function is reduced in low birth weight for gestation infants born to nonsmoking white mothers and that this is independent of somatic growth during infancy.

The effect of parental smoking on lung function and development during infancy

While the adverse effects of parental smoking on respiratory health during childhood are well recognized, its potential impact on early lung development is less clear. This review summarizes current evidence on the effect of parental smoking on lung function during infancy. It is difficult to separate the effects of pre- and postnatal exposure, since the majority of mothers who smoke in pregnancy (currently around 30% worldwide) continue to do so thereafter. Nevertheless, measurements undertaken prior to any postnatal exposure have consistently demonstrated significant changes in tidal flow patterns in infants whose mothers smoked in pregnancy. While there is, as yet, no convincing evidence from studies in human infants that smoking during pregnancy is associated with increased airway responsiveness at birth, many studies have demonstrated a reduction in forced expiratory flows (on average by 20%) in infants exposed to parental smoking. While maternal smoking during pregnancy remains the most significant source of such exposure and is likely to be responsible for diminished airway function in early life, continuing postnatal tobacco smoke exposure will increase the risk of respiratory infections, the combination of both being responsible for the two- to fourfold increased risk of wheezing illnesses observed during the first year of life in infants whose parents smoke. These findings emphasize the need to keep infants in a smoke-free environment both before and after birth, not least because of growing awareness that airway function in later life is largely determined by that during foetal development and early infancy.

Screening for "substance abuse" among school-based youth in Mexico using the Problem Oriented Screening Instrument (POSIT) for Teenagers

Indices of classification accuracy of the Substance Use/Abuse scale of a Spanish-language version of the Problem Oriented Screening Instrument for Teenagers (POSIT) were evaluated among school-based youth in Mexico. Participants were 1203 youth attending one middle school (N = 619) and one high school (N = 584) in the third largest city of Coahuila, a northern border state in Mexico in May 1998. More than 94% of youth enrolled in the participating middle school and 89% of youth enrolled in the participating high school completed the International Longitudinal Survey of Adolescent Health. Indices of classification accuracy of the POSIT Substance Use/Abuse scale were evaluated against a "drug abuse" problem severity criterion that combined youth meeting DSM-IV criteria for alcohol abuse/dependence disorders with youth having used other illicit drugs five or more times in their lifetime. The present study findings suggest that using a cut score of one or two on the POSIT Substance Use/Abuse scale generally yields optimal classification accuracy indices that vary somewhat by gender and school subgroups. Further, classification accuracy indices of the POSIT Substance Use/Abuse scale are slightly better when used among high school males due, in part, to the higher base rate of serious involvement among this group compared to others.

Latent mixed Markov modelling of smoking transitions using Monte Carlo bootstrapping

It has been established that measures and reports of smoking behaviours are subject to substantial measurement errors. Thus, the manifest Markov model which does not consider measurement error in observed responses may not be adequate to mathematically model changes in adolescent smoking behaviour over time. For this purpose we fit several Mixed Markov Latent Class (MMLC) models using data sets from two longitudinal panel studies--the third Waterloo Smoking Prevention study and the UWO smoking study, which have varying numbers of measurements on adolescent smoking behaviour. However, the conventional statistics used for testing goodness of fit of these models do not follow the theoretical chi-square distribution when there is data sparsity. The two data sets analysed had varying degrees of sparsity. This problem can be solved by estimating the proper distribution of fit measures using Monte Carlo bootstrap simulation. In this study, we showed that incorporating response uncertainty in smoking behaviour significantly improved the fit of a single Markov chain model. However, the single chain latent Markov model did not adequately fit the two data sets indicating that the smoking process was heterogeneous with regard to latent Markov chains. It was found that a higher percentage of students (except for never smokers) changed their smoking behaviours over time at the manifest level compared to the latent or true level. The smoking process generally accelerated with time. The students had a tendency to underreport their smoking behaviours while response uncertainty was estimated to be considerably less for the Waterloo smoking study which adopted the 'bogus pipeline' method for reducing measurement error while the UWO study did not. For the two-chain latent mixed Markov models, incorporating a 'stayer' chain to an unrestricted Markov chain led to a significant improvement in model fit for the UWO study only. For both data sets, the assumption for the existence of an independence chain did not lead to significant improvement in model fit. The unrestricted two-chain latent mixed Markov model led to a significant improvement of model fit compared to a simple latent Markov model, but this model was overparameterized when the latent transition probabilities and/or response probabilities were assumed nonstationary. For the other models, the manifest/latent transition probabilities and response probabilities (for the four-wave Waterloo study only) were tested to be nonstationary for both data sets.

Relative ability of full and partial forced expiratory maneuvers to identify diminished airway function in infants with cystic fibrosis

The tidal and raised volume rapid thoracoabdominal compression techniques are increasingly used to detect diminished airway function in infancy. The aim of this study was to assess the relative ability of parameters measured by these techniques to identify diminished airway function in infants newly diagnosed with cystic fibrosis (CF) with and without clinical evidence of prior lower respiratory illness. A cross-sectional, prospective study design was used in which maximal flow at functional residual capacity (VmaxFRC) from the tidal technique and FVC, FEV0.5, FEF75, and FEF25-75 from the raised volume technique were measured in 47 infants with CF and 187 healthy infants of similar body size, sex distribution, ethnic group, and exposure to maternal smoking. Multiple linear regression was used to assess group differences and to calculate SD scores for each parameter for the infants with CF. Airway function was also compared with clinical assessments of respiratory status made by pediatric pulmonologists. FEV0.5 was significantly diminished in 13 infants with CF, of whom 4 had been identified by clinicians as having normal respiratory status. Only one infant with CF had a VmaxFRC below the estimated normal range. Airway function is diminished in infants with CF irrespective of prior lower respiratory illness and in those whose respiratory status is considered normal by pediatric pulmonologists. In infants with CF, the raised volume technique identified diminished airway function more frequently than the tidal technique.

Airway function in infants newly diagnosed with cystic fibrosis

The lung function of infants with cystic fibrosis is often reduced shortly after diagnosis. We measured the airway function of newly diagnosed infants to test whether this reduction is independent of clinically recognised lower respiratory illness. We compared the airway function of 33 infants with cystic fibrosis and 87 healthy controls after adjustment for sex, age, bodyweight and length, and exposure to maternal smoking. Airway function was significantly reduced in children with cystic fibrosis, even in those without clinically recognised previous lower respiratory illness. Our findings raise important questions about the onset and natural history of impaired airway function in infants with cystic fibrosis.

The association between birthweight, sex, and airway function in infants of nonsmoking mothers

The risk of respiratory illness and death is increased in infants of low birthweight for gestational age, but the underlying physiologic mechanisms remain unclear. We examined the hypothesis that airway function is diminished in infants of low birthweight for gestational age, independent of exposure to maternal smoking. Respiratory function was measured using partial and raised volume forced expiratory maneuvers in 103 infants (> 35 wk gestation; 56 boys) not exposed pre- or postnatally to maternal smoking who, according to birthweight, were either small (SGA; n = 38) or appropriate (AGA; n = 65) for gestational age. At testing, SGA infants were of similar postnatal age (mean [SD]: SGA 6.8 [2.4] wk, AGA 5.9 [2.3] wk), but remained shorter and lighter than AGA infants. In univariate analyses, FVC, forced expired volume in 0.4 s (FEV(0.4)), and FEF(75) were significantly diminished in SGA compared with AGA infants (mean [95% CI of difference]: FVC: 127 versus 143 ml [-29, -2]; FEV(0.4): 112 versus 125 ml [-24, -2]; and FEF(75): 173 versus 203 ml s(-1) [-57, -3], respectively), but these differences were no longer significant after allowing for sex and body size. Furthermore, FEF(75) was on average 35 ml s(-1) lower in boys than girls (95% CI: -61, -8). We conclude that diminished airway function in SGA infants shortly after birth appears to be primarily mediated through impaired somatic growth.

Seasonal assessment of environmental tobacco smoke and respirable suspended particle exposures for nonsmokers in Bremen using personal monitoring

The study was designed to determine seasonal differences in personal exposures to respirable suspended particles (RSP) and environmental tobacco smoke (ETS) for nonsmokers in Bremen, Germany. The subjects were office workers, either living and working in smoking locations or living and working in nonsmoking locations. One hundred and twenty four randomly selected nonsmoking subjects collected air samples close to their breathing zone by wearing personal monitors for 24 h or, in some cases, for 7-day periods during the winter of 1999. The investigation was repeated in the summer with 126 subjects, comprised of as many of the studied winter population (89 subjects) as possible. Saliva cotinine analyses were undertaken to verify the nonsmoking status of the subjects. Subjects wore one personal monitor while at work and one while away from the workplace on weekdays, and a third monitor at the weekend. Collected air samples were analysed for RSP, nicotine, 3-ethenylpyridine (3-EP) and ETS particles. The latter were estimated using ultraviolet absorbance (UVPM), fluorescence (FPM) and solanesol (SolPM) measurements. ETS exposure was consistently higher in the winter than in the summer, this pattern being particularly evident for subjects both living and working with smokers. The highest median 24-h time weighted average (TWA) concentrations of ETS particles (SolPM, 25 microg m(-3)) and nicotine (1.3 microg m(-3)) were recorded for subjects performing weekday monitoring during the winter. These were significantly higher than equivalent levels of ETS particles (SolPM, 2.4 microg m(-3)) and nicotine (0.26 microg m(-3)) determined during the summer. There were no appreciable differences between winter and summer percent workplace contributions to median TWA ETS particle and nicotine weekday concentrations, the workplace in Bremen, in general, contributing between 35% and 61% of reported median concentrations. Workers, on average, spent one-third of their time at work during a weekday, indicating that concentrations were either comparable or higher in the workplace than in the home and other locations outside the workplace. Median 24-h weekend ETS particle and nicotine concentrations for smoking locations were not significantly different from equivalent weekday levels during the winter, but were significantly lower during the summer. Based upon median 24-h TWA SolPM and nicotine concentrations for the winter, extrapolated to 1 year's ETS exposure, those subjects both living and working in smoking locations (the most highly exposed group) would potentially inhale 13 cigarette equivalents/year (CEs/y). However, based on a similar extrapolation of summer measurements, the same group of subjects would potentially inhale between 1.3 and 1.9 CEs/y. The most highly exposed subjects in this study, based upon 90th percentile concentrations for those both living and working in smoking locations during the winter, would potentially inhale up to 67 CEs/y in the winter and up to 22 CEs/y in the summer. This clearly demonstrates that seasonal effects should be taken into account in the design and interpretation of ETS exposure studies. Air sampling over a 7-day period was shown to be technically feasible, and subsequent RSP, ETS particle and nicotine levels determined by 7-day monitoring were not found to be significantly different from equivalent levels determined by 24-h monitoring. However, the longer sampling period resulted in the collection of an increased quantity of analytes, which improved the limits of quantitation (LOQ) and allowed a more accurate determination of low level ETS exposure. This was reflected by a reduced percentage of data falling below the LOQ for 7-day monitoring compared with 24-h monitoring. The use of a liquid chromatographic method with tandem mass spectrometric detection for saliva cotinine measurement afforded a greatly improved LOQ and greater accuracy at low concentrations compared with the radioimmunoassay (RIA) method used in previous studies by these authors. In this study, 17 subjects out of 180 tested (9.4%) were found to have saliva cotinine levels exceeding the selected threshold of 25 ng ml(-1) used to discriminate between smokers and nonsmokers.

Cost effectiveness of computer tailored and non-tailored smoking cessation letters in general practice: randomised controlled trial

OBJECTIVES

To develop and evaluate, in a primary care setting, a computerised system for generating tailored letters about smoking cessation.

DESIGN

Randomised controlled trial.

SETTING

Six general practices in Aberdeen, Scotland.

PARTICIPANTS

2553 smokers aged 17 to 65.

INTERVENTIONS

All participants received a questionnaire asking about their smoking. Participants subsequently received either a computer tailored or a non-tailored, standard letter on smoking cessation, or no letter.

MAIN OUTCOME MEASURES

Prevalence of validated abstinence at six months; change in intention to stop smoking in the next six months.

RESULTS

The validated cessation rate at six months was 3.5% (30/857) (95% confidence interval 2.3% to 4.7%) for the tailored letter group, 4.4% (37/846) (3.0% to 5.8%) for the non-tailored letter group, and 2.6% (22/850) (1.5% to 3.7%) for the control (no letter) group. After adjustment for significant covariates, the cessation rate was 66% greater (-4% to 186%; P=0.07) in the non-tailored letter group than that in the no letter group. Among participants who smoked <20 cigarettes per day, the cessation rate in the non-tailored letter group was 87% greater (0% to 246%; P=0.05) than that in the no letter group. Among heavy smokers who did not quit, a 76% higher rate of positive shift in "stage of change" (intention to quit within a particular period of time) was seen compared with those who received no letter (11% to 180%; P=0.02). The increase in cost for each additional quitter in the non-tailored letter group compared with the no letter group was pound 89.

CONCLUSIONS

In a large general practice, a brief non-tailored letter effectively increased cessation rates among smokers. A tailored letter was not effective in increasing cessation rates but promoted shift in movement towards cessation ("stage of change") in heavy smokers. As a pragmatic tool to encourage cessation of smoking, a mass mailing of non-tailored letters from general practices is more cost effective than computer tailored letters or no letters.

Children's exposure to passive smoking in England since the 1980s: cotinine evidence from population surveys

OBJECTIVE

To determine whether children's exposure to passive smoking has changed since the late 1980s.

DESIGN

Cross sectional surveys of nationally representative samples of secondary school children carried out between 1988 and 1998 by Office for National Statistics.

SETTING

England.

SUBJECTS

Secondary school children aged 11-15.

MAIN OUTCOME MEASURES

Salivary cotinine concentrations in non-smoking children.

RESULTS

Cotinine concentrations in all non-smoking children almost halved between 1988 and 1998, from a geometric mean of 0.96 (95% confidence interval 0.83 to 1.11) ng/ml in 1988 to 0.52 (0.43 to 0.62) ng/ml in 1998. This reduction was largely due to reductions in exposure in children from non-smoking households and to decreases in the percentage of parents who smoked. Children living with mothers or fathers who smoked experienced little reduction in exposure.

CONCLUSIONS

Exposure to passive smoking among children in England has approximately halved since the late 1980s. This reduction is partly explained by the fall in the percentage of both mothers and fathers who smoke and is also likely to reflect reductions of smoking in public places. However, there is only limited evidence that children from smoking households have experienced a reduction in exposure through parents' avoidance of smoking in their presence.

Initial tobacco use episodes in children and adolescents: current knowledge, future directions

Approximately three-quarters of adult tobacco users report that their first tobacco use occurred between ages 11 and 17, while many adults who do not regularly use tobacco report that they experimented with it as adolescents. Surprisingly little is known about the effects of these initial tobacco use episodes and their influence on adult tobacco use patterns. In particular, understanding the role that nicotine plays in these early tobacco use experiences may be important in understanding the development of regular tobacco use and concomitant nicotine dependence. One goal of this review is to summarize current knowledge regarding the effects of initial tobacco use episodes in adolescents and to discuss nicotine exposure in initial tobacco use episodes. Another goal is to outline a research agenda designed to learn more about initial tobacco use episodes and the effects of nicotine in children. An ethical rationale and some potential methods for this research agenda are presented.

Anonymity and Confidentiality in School Surveys on Alcohol, Tobacco, and Cannabis Use

School surveys are currently the most important method of collecting data on alcohol and drug use among youth. Although methodological studies suggest that school surveys yield reliable and valid estimates of substance use among youth, it has been argued that results will be affected by the level of perceived anonymity. Longitudinal research designs raise an important question in this respect since follow-up makes complete anonymity impossible. In fact, responses to such surveys should be regarded as confidential rather than anonymous. This study compares the reported use of cigarettes, alcohol and cannabis between an anonymous, cross-sectional survey and a confidential, longitudinal survey. Both females and males in the confidential survey have a slightly higher rate of non-response for lifetime cannabis use. Furthermore, females tend to be slightly less likely to admit to any use of alcohol and cannabis in the confidential survey, and those who do admit to having used cigarettes and alcohol, report slightly fewer occasions. The correlations between use of cigarettes, alcohol, and cannabis are not affected by this bias. These results add further support to earlier research that has found school surveys to be a robust method of data collection, and suggests that the bias introduced by identification numbers in longitudinal research has limited practical significance.

Tobacco smoke exposure in children and adolescents with diabetes mellitus

AIMS

To examine active and passive tobacco smoke exposure in children and adolescents attending a diabetic clinic.

METHODS

Salivary cotinine concentrations were measured by gas chromatography and questionnaire data on the smoking habits of patients, families and friends were analysed as well as recording of glycosylated haemoglobin (HbA1c), body mass index (BMI) and social deprivation score.

RESULTS

Salivary cotinine concentrations identified 7% of the patients as active smokers and 72% as passive smokers. The mean cotinine concentration in those with no identifiable source of exposure was 0.10 (95% confidence interval 0.05-0.14) ng/ml, 2.81 (2.24-3.38) ng/ml in the passive smoking group and 1003.69 (55.96-151.41) ng/ml in the active smokers. Cotinine concentrations in passive smokers increased with the number of sources of exposure. The mean cotinine concentration was also higher when the mother was the sole source compared to other sources. There was no statistically significant correlation to smoking exposure and HbA1c BMI and deprivation scores.

CONCLUSION

Tobacco smoke exposure may pose serious health risks to children and adolescents with diabetes and additional public health measures are required to reduce overall exposure.

Testing for drugs of abuse in saliva and sweat

The detection of marijuana, cocaine, opiates, amphetamines, benzodiazepines, barbiturates, PCP, alcohol and nicotine in saliva and sweat is reviewed, with emphasis on forensic applications. The short window of detection and lower levels of drugs present compared to levels found in urine limits the applications of sweat and saliva screening for drug use determination. However, these matrices may be applicable for use in driving while intoxicated and surveying populations for illicit drug use. Although not an illicit drug, the detection of ethanol is reviewed because of its importance in driving under the influence. Only with alcohol may saliva be used to estimate blood levels and the degree of impairment because of the problems with oral contamination and drug concentrations varying depending upon how the saliva is obtained. The detection of nicotine and cotinine (from smoking tobacco) is also covered because of its use in life insurance screening and surveying for passive exposure.

What determines levels of passive smoking in children with asthma?

BACKGROUND

Children with parents who smoke are often exposed to high levels of environmental tobacco smoke, and children with asthma are particularly susceptible to the detrimental effects of passive smoking. Data were collected from parents who smoke and from their asthmatic children. The families are currently taking part in a randomised controlled trial to test an intervention designed to reduce passive smoking in children with asthma. This paper reports on the baseline data. Questionnaire data and cotinine levels were compared in an attempt to assess exposure and to identify factors which influence exposure of the children. The aim of the study was to identify the scope for a reduction in passive smoking by these children.

METHODS

A sample of 501 families with an asthmatic child aged 2-12 years was obtained. Factors influencing passive smoking were assessed by interviewing parents. Cotinine levels were measured from saliva samples using gas liquid chromatography with nitrogen phosphorous detection.

RESULTS

Cotinine levels in children were strongly associated with the age of the child, the number of parents who smoked, contact with other smokers, the frequency of smoking in the same room as the child, and crowding within the home. Parental cotinine levels, the amount smoked in the home, and whether the home had a garden also exerted an independent effect on cotinine levels in the children.

CONCLUSIONS

Many children are exposed to high levels of environmental tobacco smoke and their cotinine levels are heavily dependent upon proximity to the parent who smokes. Parents who smoke have a unique opportunity to benefit their child's health by modifying their smoking habits within the home.

Assessment of air quality in Stockholm by personal monitoring of nonsmokers for respirable suspended particles and environmental tobacco smoke

Exposure to respirable suspended particles (RSP) from all sources and environmental tobacco smoke (ETS) was assessed for 190 nonsmokers in Stockholm during 1994. Each subject wore a personal monitor for 24-h, provided saliva samples for cotinine analysis, and completed a detailed questionnaire about air quality and life-style. The subjects consisted of housewives and househusbands in one main group and working men and women in the second. The housewives and househusbands wore a single monitor throughout the 24-h period and the working subjects wore one monitor at work and a separate monitor while not at work. The geodemographic distribution of the recruited subjects accurately reflected the population of Stockholm. For most of the subjects, exposure to ETS and nicotine was at or below the limits of quantification (LOQ). This finding was supported by the fact that about 80% of the recruited subjects claimed that their exposure to ETS was "none" or "low". The concentration of RSP was found to be highest (median 39 micrograms.m-3) in homes where smoking occurred and below the LOQ in the workplace irrespective of its smoking status. These levels are at the lowest end of typical indoor air levels for RSP. For the housewives and househusbands living in smoking homes (nonsmoking homes in parentheses), the median exposure levels were 39 micrograms.m-3 (18 micrograms.m-3) for RSP, 17 micrograms . m-3 (0.12 micrograms . m-3) for ETS particles, and 1.1 micrograms.m-3 (0.05 micrograms.m-3) for nicotine. Both the pre- and postmonitoring continine saliva levels measured for these housewives and househusbands were 2.9 ng.ml-1 (pre-0.56 ng.ml-1, post-0.41 ng.ml-1). The highest exposure levels were recorded for the housewives and househusbands in the age range of 35-49 years. For the working subjects, the exposure measured in smoking workplaces (nonsmoking workplaces in parentheses) gave median levels of 16 micrograms.m-3 (16 micrograms.m-3) for RSP, 1.1 micrograms.m-3) for ETS particles and 0.2 micrograms.m-3 (0.15 microgram.m-3) for nicotine. Similarly measured exposures at home (nonsmoking homes in parentheses), including all other locations outside the workplace, gave median levels of 24 micrograms.m-3 (19 micrograms.m-3) for RSP, 1.4 micrograms. m-3 (0.2 microgram.m-3) for ETS particles, and 0.15 microgram.m-3 (0.07 microgram.m-3) for nicotine. Overall, the exposure levels of ETS due to living with smokers in Stockholm was found to be much lower than similar exposures measured previously in the United Kingdom and the United States. Over 70% of all the nicotine measurements and 60% of all the ETS measurements were below the LOQ. When the median values for nicotine and ETS particles are converted to cigarette equivalents, Stockholm housewives and househusbands living with smokers would receive 6-9 cigarette equivalents per year, working nonsmokers living with smokers would receive 0.6-0.7 cigarette equivalents at home, and nonsmokers working with smokers would be exposed to 0.1-0.2 cigarette equivalent at work. The exposures were therefore up to six times greater at home than in workplaces where smoking was occurring. Although all the subjects were recruited as nonsmokers on the basis of their self-reported nonsmoking status, saliva continine measurements were used for confirmation. Subjects with continine levels below 25 ng.ml-1 were considered to be nonsmokers although the selection of a threshold level within the range of 10-50 ng.ml-1 was not considered to be critical. With a threshold of 25 ng.ml-1, between 2.7% and 5.3% were later shown to be misclassified as nonsmokers, depending on the definition of misclassification used. During the study period the air quality in Stockholm could be described according a British nomenclature as "very good" for the majority of the time. The daily average at no time fell below "good," and the maximum hourly nitrogen dioxide level was 111 micrograms.m-3 (inner city at street level) on the coldest day

Transitions to cigarette smoking during adolescence

The process of transition from nonsmoking to regular weekly smoking during a period from 10 to 16 years was examined using data gathered during the course of a longitudinal study of 957 New Zealand adolescents. These data were analyzed using a latent Markov model to estimate both rates of transition between stages of smoking and errors of measurement in report data. The fitted model suggested that the process of transition to smoking was a progressive and one-way process in which once teenagers had graduated to a given smoking status, return to earlier stages was uncommon. This process also showed a clear tendency to accelerate with age, so that rates of transition to smoking behaviors after the age of 14 years were far higher than rates of transition at age 10 years. The model also made it possible to estimate the accuracy of smoking reports. This suggested that individuals who were nonsmokers or regular smokers were classified with better than 95% accuracy on the basis of report data. However, the reporting accuracy of occasional smoking was poor, with 42% of occasional smokers being falsely classified as nonsmokers. The implications of these findings for the understanding of the processes of transition to smoking behaviors and the effects of measurement errors in report data are discussed.

The validity of self-reported smoking: a review and meta-analysis

OBJECTIVES

The purpose of this study was to identify circumstances in which biochemical assessments of smoking produce systematically higher or lower estimates of smoking than self-reports. A secondary aim was to evaluate different statistical approaches to analyzing variation in validity estimates.

METHODS

Literature searches and personal inquiries identified 26 published reports containing 51 comparisons between self-reported behavior and biochemical measures. The sensitivity and specificity of self-reports of smoking were calculated for each study as measures of accuracy.

RESULTS

Sensitivity ranged from 6% to 100% (mean = 87.5%), and specificity ranged from 33% to 100% (mean = 89.2%). Interviewer-administered questionnaires, observational studies, reports by adults, and biochemical validation with cotinine plasma were associated with higher estimates of sensitivity and specificity.

CONCLUSIONS

Self-reports of smoking are accurate in most studies. To improve accuracy, biochemical assessment, preferably with cotinine plasma, should be considered in intervention studies and student populations.

The validity of self-reported smoking: a review and meta-analysis

OBJECTIVES

The purpose of this study was to identify circumstances in which biochemical assessments of smoking produce systematically higher or lower estimates of smoking than self-reports. A secondary aim was to evaluate different statistical approaches to analyzing variation in validity estimates.

METHODS

Literature searches and personal inquiries identified 26 published reports containing 51 comparisons between self-reported behavior and biochemical measures. The sensitivity and specificity of self-reports of smoking were calculated for each study as measures of accuracy.

RESULTS

Sensitivity ranged from 6% to 100% (mean = 87.5%), and specificity ranged from 33% to 100% (mean = 89.2%). Interviewer-administered questionnaires, observational studies, reports by adults, and biochemical validation with cotinine plasma were associated with higher estimates of sensitivity and specificity.

CONCLUSIONS

Self-reports of smoking are accurate in most studies. To improve accuracy, biochemical assessment, preferably with cotinine plasma, should be considered in intervention studies and student populations.

Passive exposure to tobacco smoke in children aged 5-7 years: individual, family, and community factors

OBJECTIVE

To examine the importance of parental smoking on passive exposure to tobacco smoke in children and the social and geographical patterns of exposure.

DESIGN

Cross sectional study.

SETTING

Schools in 10 towns in England and Wales; five towns with high adult cardiovascular mortality and five with low rates.

SUBJECTS

4043 children aged 5-7 years of European origin.

MAIN OUTCOME MEASURES

Salivary cotinine concentration and parents self reported smoking habits.

RESULTS

1061 (53.0%) children were exposed to cigarette smoke at home or by an outside carer. Geometric mean cotinine rose from 0.29 (95% confidence interval 0.28 to 0.31) ng/ml in children with no identified exposure to 4.05 (3.71 to 4.42) ng/ml in households where both parents smoked and 9.03 (6.73 to 12.10) ng/ml if both parents smoked more than 20 cigarettes a day. The effect of mothers' smoking was greater than that of fathers', especially at high levels of consumption. After adjustment for known exposures geometric mean cotinine concentrations rose from 0.52 ng/ml in social class I to 1.36 ng/ml in social class V (P < 0.0001); and were doubled in high mortality towns compared with the low mortality towns (P = 0.002). In children with no identified exposure similar trends by social class and town were observed and the cotinine concentrations correlated with the prevalence of parental smoking, both between towns (r = 0.69, P = 0.02) and between schools within towns (r = 0.50, P < 0.001).

CONCLUSIONS

Mothers' smoking is more important that fathers' despite the lower levels of smoking by mothers. Children not exposed at home had low cotinine concentration, the level depending on the prevalence of smoking in the community.

Ultralight cigarettes: activity, cardiovascular, dietary, and subjective parameters

In a field study, 24-h heart rate, physical activity, and cigarette consumption were continuously recorded, whereas resting heart rate, blood pressure, dietary intake, and subjective parameters were assessed six times per day. Smoking habitual and ultralight cigarettes for two days each was compared in a sample of 48 smokers, consisting of 24 office and 24 nonoffice workers of both sexes. Nonoffice workers smoked more and revealed higher respiratory CO and Fagerstrom index values, whereas other group differences were unrelated to smoking or its effects. Switching to ultralight cigarettes with four- to eightfold lower nicotine yields than the habitual cigarettes significantly decreased respiratory CO by 5 ppm, saliva cotinine by 30%, resting heart rate by 2.5 bpm, systolic blood pressure by 3.5 mmHg, and diastolic blood pressure by 3.0 mmHg, but increased fat intake by about 400 kJ, whereas activity and subjective well-being were not affected. Thus, the reduction in saliva cotinine was considerably smaller than the reduction in nicotine yield, and the effects on physiological parameters therefore were rather modest.

Relation of passive smoking as assessed by salivary cotinine concentration and questionnaire to spirometric indices in children

BACKGROUND

Previous studies of the effects of passive exposure to smoke on spirometric indices in children have largely relied on questionnaire measures of exposure. This may have resulted in underestimation of the true effect of passive smoking. Biochemical measures offer the opportunity to estimate recent exposure directly.

METHODS

The relation between spirometric indices and passive exposure to tobacco smoke was examined in a large population sample of 5-7 year old children from 10 towns in England and Wales. The effects of passive exposure to smoke on lung function were assessed by means of both salivary cotinine concentration and questionnaire measurements of exposure. Analyses of the relation between spirometric values and cotinine concentrations were based on 2511 children and of the relation between spirometric values and questionnaire measures on 2000 children.

RESULTS

Cotinine concentration was negatively associated with all spirometric indices after adjustment for confounding variables, which included age, sex, body size, and social class. The strongest association was with mid expiratory flow rate (FEF50), the fall between the bottom and top fifths of the cotinine distribution being 6%, equivalent to a reduction of 14.3 (95% confidence limits (CL) 8.6, 20.0) ml/s per ng/ml cotinine. Salivary cotinine concentrations were strongly related to exposure to cigarette smoke at home but 88% of children who were from non-smoking households and not looked after by a smoker had detectable cotinine concentrations, 5% being in the top two fifths of the cotinine distribution. A composite questionnaire score based on the number of regular sources of exposure was as strongly related to mid and end expiratory flow rates as the single cotinine measure. The fall in FEF50 per smoker to whom the child was exposed was 51.0 (26.5, 75.5) ml/s. The relationships between the questionnaire score and forced vital capacity (FVC) or forced expiratory volume in one second (FEV1) were not statistically significant.

CONCLUSIONS

These effects of passive smoking on respiratory function are consistent with the results of previous studies and, although small in absolute magnitude, may be important if the effects of exposure are cumulative. In children aged 5-7 years the use of a single salivary cotinine concentration as a marker of passive exposure to smoke resulted in clear relationships between exposure and FVC and FEV1, whereas the associations were much weaker and not significant when based on the questionnaire score. The associations between exposure and mid or end expiratory flow rates were of similar magnitude for cotinine concentration and the questionnaire score. The use of salivary cotinine concentration in longitudinal studies may help to determine the extent to which these effects are cumulative or reversible.

Determinants of passive smoking in children in Edinburgh, Scotland

OBJECTIVES

Using saliva cotinine as a quantitative marker, we examined the contribution of factors other than parental smoking to children's passive exposure to tobacco smoke.

METHODS

Saliva specimens from a random sample of 734 7-year-old schoolchildren in Edinburgh, Scotland, were analyzed for cotinine. Their parents completed a questionnaire covering smoking habits and conditions in the home.

RESULTS

A number of independent predictors of cotinine were identified in addition to the main one of smoking by household members. These predictors included home ownership, social class, day of the week, season of the year, number of parents present, crowding in the home, the number of children in the household, and sex. Cotinine was higher in children from less advantaged backgrounds, during winter, on Mondays, in girls, and when fewer other children were present. The effects were similar between children from nonsmoking and smoking homes.

CONCLUSIONS

Questionnaire measures of parental smoking are insufficient to fully characterize young children's exposure to passive smoking. Because socioeconomic variables contribute to measured exposure, passive-smoking studies that treat class as a confounder and control for it may be overcontrolling.

Cotinine in an ultrafiltrate of saliva

BACKGROUND

We have developed a device for the simplified collection of a prepurified sample of saliva in the mouth.

METHOD

The device is based on the principle of an osmotic pump and accumulated about 1.2 ml of an ultrafiltrate of saliva within 8 min. We have investigated the ultrafiltrate for its utility as a biological medium in the evaluation of cigarette smoking status.

RESULTS

(a) In 58 matched samples from 13 subjects, the correlation coefficient for the cotinine concentration in the saliva and the ultrafiltrate was 0.95; (b) in matched plasma and ultrafiltrate samples from 27 smokers, the correlation coefficient for the cotinine concentrations was 0.96 with plasma containing 1.2 times the ultrafiltrate mean; (c) in a nonsmoker, elevated cotinine levels could be detected in the ultrafiltrate more than 24 hr after smoking 2 cigarettes, and the pattern of rise and decrease reflected that in whole saliva; and (d) in a habitual smoker; the mean cotinine concentration in the ultrafiltrate was 157 ng/ml (SD +/- 25.7 ng/ml) during a period of smoking 15 cigarettes per day and dropped to a mean of 47 ng/ml (SD +/- 10.5) when smoking was reduced to 5 cigarettes per day; after cessation of smoking, detectable concentrations of cotinine persisted for up to 5 days.

CONCLUSION

The device facilitated the aesthetic, noninvasive collection of a biological sample useful in the validation of smoking status.

Adolescent smokers seen in general practice: health, lifestyle, physical measurements, and response to antismoking advice

OBJECTIVE

To compare physical, lifestyle, and health characteristics of adolescent smokers and non-smokers and their initial response to anti-smoking counselling.

DESIGN

Adolescents aged 13, 15, and 17 years were identified from age-sex registers and invited by letter for a general practice health check.

SETTING

Three general practices in the MRC general practice research framework.

MAIN OUTCOME MEASURES

Blood pressure, body mass index, saliva cotinine concentration, peak flow rate, alcohol consumption, exercise, duration of sleep, and stated persistent health problems.

RESULTS

73% of the adolescents (491) attended for the health check. A total of 68 (14%) were regular smokers. By age 17 those who smoked regularly had a significantly lower systolic blood pressure than those who had never smoked regularly (by 6 mm Hg; p = 0.025) despite a significantly higher body mass index (by 1.5; p <0.001) [corrected]. Cotinine concentrations increased with smoking exposure, from 0.7 ng/ml when no family member smoked to 155 ng/ml in active smokers of six or more cigarettes a week. Significantly more regular smokers than never regular smokers drank greater than or equal to 8 g alcohol a day (chi 2 = 15.2 adjusted for age and sex p less than 0.001); regular smokers exercised less (1.0 hrs/week in boys and 0.8 hrs/week in girls v 3.4 hrs/week in boys and 2.2 hrs/week in girls; p less than 0.001) and slept less (8.0 hrs/night v 8.5 hrs/night at age 17; p less than 0.005). Persistent health problems, mostly asthma or allergic symptoms, were reported by 25% (17/68) of the smokers and 16% (60/381) of the non-smokers. Of the smokers given counselling, 60% (26/43) made an agreement with the practice doctor or nurse to give up smoking.

CONCLUSION

General practice is an appropriate setting for adolescents to receive advice on healthy lifestyle, which should not focus solely on smoking.

Smoking during pregnancy and its effects on child cognitive ability from the ages of 8 to 12 years

Maternal smoking during pregnancy and subsequent child cognitive development and ability were examined in a birth cohort of New Zealand children studied to the age of 12 years. Analysis at a bivariate level showed that children whose mothers smoked during pregnancy scored significantly lower on standardised tests of intelligence, reading and mathematical ability than children whose mothers did not smoke. However, after adjustment for confounding covariates, the results showed no detectable relationship between smoking during pregnancy and child cognitive ability. These results suggest that children whose mothers smoked during pregnancy fared worse on tests of cognitive ability not because of possible causal effects of smoking, but rather because these children tended to come from families which provided a relatively disadvantaged home environment.

A review of the use of saliva cotinine as a marker of tobacco smoke exposure

Cotinine, the major metabolite of nicotine, is a useful marker of exposure to tobacco smoke. It can be measured in plasma, urine, or saliva. However, distinguishing between active and passive smoking on the basis of a cotinine measurement may be difficult. In order to evaluate the relationship between saliva cotinine concentration and self-reported tobacco smoke exposure in both active and passive smokers, an English-language literature search using MEDLINE was conducted (1973-1989), and the bibliographies of identified articles were reviewed. Of 43 originally identified articles, only 22 met the criteria for inclusion. Specific information regarding population studied, reported tobacco smoke exposure, method of measurement, and cotinine concentrations was assessed. Passive smokers usually have cotinine concentrations in saliva below 5 ng/ml, but heavy passive exposure can result in levels greater than or equal to 10 ng/ml. Levels between 10 and 100 ng/ml may result from infrequent active smoking or regular active smoking with low nicotine intake. Levels greater than 100 ng/ml are probably the result of regular active smoking. Four categorizations of tobacco smoke exposure are suggested on the basis of saliva cotinine concentrations.

The nicotine addiction trap: a 40-year sentence for four cigarettes

It is generally recognized that smoking causes more preventable illness than any other form of drug addiction. Despite this, and unlike the case with other addictions, few services are provided to help people to give it up. Yet nicotine is highly addictive. Its role in the recruitment process, the development of dependence and as a block to smoking cessation are discussed within the context of the typical smoking career. Over 90% of teenagers who smoke 3-4 cigarettes are trapped into a career of regular smoking which typically lasts for some 30-40 years. Only 35% of regular smokers succeed in stopping permanently before the age of 60, although the large majority want to stop and try to stop. The pharmacological effects of nicotine and other factors that determine dependence on smoking, together with the attitudinal and cognitive factors that determine motivation to stop smoking, are considered within the framework of a decision-making model which reflects the cycles of change in smoking status at different stages of the smoking career. It is argued that, in future intervention strategies, the newly developed treatment approaches should be included to complement traditional motivational approaches based on educational and restrictive measures.

A latent class model of smoking experimentation in children

A latent class model to estimate the accuracy of reports of child smoking behaviour is presented. This model was fitted to data for a sample of 810 9-yr-old New Zealand children. The model suggested that errors of measurement in reports of child smoking largely arose from false negative responses in which children who had smoked described themselves as not smoking: false negative rates were in the region of 40%. The consequences of the high false negative rates are shown to lead to an underestimation of the prevalence of smoking experimentation and of the strength of association between maternal and child smoking.