California Children's Health Study Research Articles

Perceived Stress From Childhood to Adulthood and Cardiometabolic End Points in Young Adulthood: An 18-Year Prospective Study.

We investigated how childhood-to-adulthood perceived stress patterns predict adult cardiometabolic risk. This study included 276 participants from the Southern California Children's Health Study (2003-2014), and a follow-up assessment (2018-2021). Perceived stress (Perceived Stress Scale) was initially reported by participants' parents for themselves during early childhood (mean age, 6.3 years), and later self-reported during adolescence (13.3 years) and young adulthood (23.6 years). Participants were grouped into 4 stress patterns: consistently high, decreasing, increasing, and consistently low. Cardiometabolic risk was assessed in young adulthood by carotid artery intima-media thickness, systolic and diastolic blood pressure, obesity, percent body fat, android/gynoid ratio, and glycated hemoglobin. A cardiometabolic risk score was generated by summing the clinically abnormal markers. Multivariable linear and logistic regression models were used to (1) examine the associations between Perceived Stress Scale at 3 time points and adult cardiometabolic risk, and (2) assess the impact of stress pattern on adult cardiometabolic risk. Findings suggested that in adulthood, higher Perceived Stress Scale score was associated with increased overall cardiometabolic risk (β=0.12 [95% CI, 0.01-0.22]), carotid artery intima-media thickness (β=0.01 [95% CI, 0.0003-0.02]), systolic blood pressure (β=1.27 [95% CI, 0.09-2.45]), and diastolic blood pressure (β=0.94 [95% CI, 0.13-1.75]). Individuals with a consistently high adolescence-to-adulthood stress patternhad greater overall cardiometabolic risk (β=0.31 [95% CI, 0.02-0.60]), android/gynoid ratio (β=0.07 [95% CI, 0.02-0.13]), percent body fat (β=2.59 [95% CI, 0.01-5.17]), and greater odds of obesity (odds ratio, 5.57 [95% CI, 1.62-19.10]) in adulthood, compared with those with a consistently low Perceived Stress Scale score. Consistently high perceived stress from adolescence to adulthood may contribute to greater cardiometabolic risk in young adulthood.

Exposure to perfluoroalkyl substances and longitudinal changes in bone mineral density in adolescents and young adults: A multi-cohort study

BackgroundPer- and polyfluoroalkyl substances (PFAS) may impair bone development in adolescence, which impacts life-long bone health. No previous studies have examined prospective associations of individual PFAS and their mixture with bone mineral density (BMD) changes in Hispanic young persons, a population at high risk of osteoporosis in adulthood. ObjectivesTo examine associations of individual PFAS and PFAS mixtures with longitudinal changes in BMD in an adolescent Hispanic cohort and examine generalizability of findings in a mixed-ethnicity young adult cohort (58.4% Hispanic). MethodsOverweight/obese adolescents from the Study of Latino Adolescents at Risk of Type 2 Diabetes (SOLAR; n = 304; mean follow-up = 1.4 years) and young adults from the Southern California Children's Health Study (CHS; n = 137; mean follow-up = 4.1 years) were included in this study. Plasma PFAS were measured at baseline and dual x-ray absorptiometry scans were performed at baseline and follow-up to measure BMD. We estimated longitudinal associations between BMD and five PFAS via separate covariate-adjusted linear mixed effects models, and between BMD and the PFAS mixture via quantile g-computation. ResultsIn SOLAR adolescents, baseline plasma perfluorooctanesulfonic acid (PFOS) was associated with longitudinal changes in BMD. Each doubling of PFOS was associated with an average −0.003 g/cm2 difference in change in trunk BMD per year over follow-up (95% CI: −0.005, −0.0002). Associations with PFOS persisted in CHS young adults, where each doubling of plasma PFOS was associated with an average −0.032 g/cm2 difference in total BMD at baseline (95% CI -0.062, −0.003), though longitudinal associations were non-significant. We did not find associations of other PFAS with BMD; associations of the PFAS mixture with BMD outcomes were primarily negative though non-significant. DiscussionPFOS exposure was associated with lower BMD in adolescence and young adulthood, important periods for bone development, which may have implications on future bone health and risk of osteoporosis in adulthood.

Disparities in greenspace associated with sleep duration among adolescent children in Southern California.

In 2010, a total of 1476 Southern California Children's Health Study (CHS) participants in grades 9 and 10 (mean age, 13.4 years; SD, 0.6) completed a questionnaire including topics on sleep and psychosocial stress. Exposures to greenspace, artificial light at night (ALAN), nighttime noise, and air pollution were estimated at each child's residential address, and SES was characterized by maternal education. Odds ratios and 95% confidence intervals (95% CIs) for sleep outcomes were estimated by environmental exposure, adjusting for age, sex, race/ethnicity, home secondhand smoke, and SES. An interquartile range (IQR) increase in greenspace decreased the odds of not sleeping at least 8 hours (odds ratio [OR], 0.86 [95% CI, 0.71, 1.05]). This association was significantly protective in low SES participants (OR, 0.77 [95% CI, 0.60, 0.98]) but not for those with high SES (OR, 1.16 [95%CI, 0.80, 1.70]), interaction P = 0.03. Stress mediated 18.4% of the association among low SES participants. Residing in urban neighborhoods of greater greenness was associated with improved sleep duration among children of low SES but not higher SES. These findings support the importance of widely reported disparities in exposure and access to greenspace in socioeconomically disadvantaged populations.

Metabolic Signatures of Youth Exposure to Mixtures of Per- and Polyfluoroalkyl Substances: A Multi-Cohort Study.

Exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous and has been associated with an increased risk of several cardiometabolic diseases. However, the metabolic pathways linking PFAS exposure and human disease are unclear. We examined associations of PFAS mixtures with alterations in metabolic pathways in independent cohorts of adolescents and young adults. Three hundred twelve overweight/obese adolescents from the Study of Latino Adolescents at Risk (SOLAR) and 137 young adults from the Southern California Children's Health Study (CHS) were included in the analysis. Plasma PFAS and the metabolome were determined using liquid-chromatography/high-resolution mass spectrometry. A metabolome-wide association study was performed on log-transformed metabolites using Bayesian regression with a g-prior specification and g-computation for modeling exposure mixtures to estimate the impact of exposure to a mixture of six ubiquitous PFAS (PFOS, PFHxS, PFHpS, PFOA, PFNA, and PFDA). Pathway enrichment analysis was performed using Mummichog and Gene Set Enrichment Analysis. Significance across cohorts was determined using weighted -tests. In the SOLAR and CHS cohorts, PFAS exposure was associated with alterations in tyrosine metabolism (meta-analysis ) and de novo fatty acid biosynthesis (), among others. For example, when increasing all PFAS in the mixture from low (th percentile) to high (th percentile), thyroxine (T4), a thyroid hormone related to tyrosine metabolism, increased by 0.72 standard deviations (SDs; equivalent to a standardized mean difference) in the SOLAR cohort (95% Bayesian credible interval (BCI): 0.00, 1.20) and 1.60 SD in the CHS cohort (95% BCI: 0.39, 2.80). Similarly, when going from low to high PFAS exposure, arachidonic acid increased by 0.81 SD in the SOLAR cohort (95% BCI: 0.37, 1.30) and 0.67 SD in the CHS cohort (95% BCI: 0.00, 1.50). In general, no individual PFAS appeared to drive the observed associations. Exposure to PFAS is associated with alterations in amino acid metabolism and lipid metabolism in adolescents and young adults. https://doi.org/10.1289/EHP11372.

Plasma concentrations of lipophilic persistent organic pollutants and glucose homeostasis in youth populations

BackgroundExposure to lipophilic persistent organic pollutants (POPs) is ubiquitous. POPs are metabolic disrupting chemicals and are potentially diabetogenic. MethodsUsing a multi-cohort study including overweight adolescents from the Study of Latino Adolescents at Risk (SOLAR, N = 301, 2001–2012) and young adults from the Southern California Children's Health Study (CHS, N = 135, 2014–2018), we examined associations of POPs and risk factors for type 2 diabetes. SOLAR participants underwent annual visits for a median of 2.2 years and CHS participants performed a single visit, during which a 2-h oral glucose tolerance test was performed. Linear mixed models were used to examine associations between plasma concentrations of POPs [4,4′-dichlorodiphenyldichloroethylene (4,4′-DDE), hexachlorobenzene (HCB), PCBs-153, 138, 118, 180 and PBDEs-154, 153, 100, 85, 47] and changes in glucose homeostasis across age and pubertal stage. ResultsIn SOLAR, exposure to HCB, PCB-118, and PBDE-153 was associated with dysregulated glucose metabolism. For example, each two-fold increase in HCB was associated with approximately 2 mg/dL higher glucose concentrations at 30 min (p = 0.001), 45 min (p = 0.0006), and 60 min (p = 0.03) post glucose challenge. Compared to individuals with low levels of PCB-118, individuals with high levels exhibited a 4.7 mg/dL (p = 0.02) higher glucose concentration at 15 min and a 3.6 mg/dL (p = 0.01) higher glucose concentration at 30 min. The effects observed with exposure to organochlorine compounds were independent of pubertal stages. PBDE-153 was associated with the development of dysregulated glucose metabolism beginning in late puberty. At Tanner stage 4, exposure to PBDE-153 was associated with a 12.7 mg/dL higher 60-min glucose concentration (p = 0.009) and a 16.1 mg*dl−1*hr−1 higher glucose AUC (p = 0.01). These associations persisted at Tanner 5. In CHS, PBDE-153 and total PBDE were associated with similar increases in glucose concentrations. ConclusionOur results suggest that childhood exposure to lipophilic POPs is associated with dysregulated glucose metabolism.

Exposure to Perfluoroalkyl Substances and Glucose Homeostasis in Youth.

Background:Exposure to per- and polyfluoroalkyl substances (PFAS), a prevalent class of persistent pollutants, may increase the risk of type 2 diabetes.Objective:We examined associations between PFAS exposure and glucose metabolism in youth.Methods:Overweight/obese adolescents from the Study of Latino Adolescents at Risk of Type 2 Diabetes (SOLAR; ) participated in annual visits for an average of . Generalizability of findings were tested in young adults from the Southern California Children’s Health Study (CHS; ) who participated in a clinical visit with a similar protocol. At each visit, oral glucose tolerance tests were performed to estimate glucose metabolism and function via the insulinogenic index. Four PFAS were measured at baseline using liquid chromatography–high-resolution mass spectrometry; high levels were defined as concentrations percentile.Results:In females from the SOLAR, high perfluorohexane sulfonate (PFHxS) levels () were associated with the development of dysregulated glucose metabolism beginning in late puberty. The magnitude of these associations increased postpuberty and persisted through 18 years of age. For example, postpuberty, females with high PFHxS levels had higher 60-min glucose (95% CI: ; ), higher 2-h glucose (95% CI: ; ), and 25% lower function () compared with females with low levels. Results were largely consistent in the CHS, where females with elevated PFHxS levels had higher 60-min glucose (95% CI: ; ) and higher 2-h glucose, which did not meet statistical significance (95% CI: ; ). In males, no consistent associations between PFHxS and glucose metabolism were observed. No consistent associations were observed for other PFAS and glucose metabolism.Discussion:Youth exposure to PFHxS was associated with dysregulated glucose metabolism in females, which may be due to changes in function. These associations appeared during puberty and were most pronounced postpuberty. https://doi.org/10.1289/EHP9200

E-cigarette Product Characteristics and Subsequent Frequency of Cigarette Smoking.

There is a dearth of evidence regarding the association of use of electronic cigarettes (e-cigarettes) with certain product characteristics and adolescent and young adult risk of unhealthy tobacco use patterns (eg, frequency of combustible cigarette smoking), which is needed to inform the regulation of e-cigarettes. Data were collected via an online survey of participants in the Southern California Children's Health Study from 2015 to 2016 (baseline) and 2016 to 2017 (follow-up) (N = 1312). We evaluated the association of binary categories of 3 nonmutually exclusive characteristics of the e-cigarette used most frequently with the number of cigarettes smoked in the past 30 days at 1-year follow-up. Product characteristics included device (vape pen and/or modifiable electronic cigarette [mod]), use of nicotine in electronic liquid (e-liquid; yes or no), and use for dripping (directly dripping e-liquid onto the device; yes or no). Relative to never e-cigarette users, past-30-day e-cigarette use was associated with greater frequency of past-30-day cigarette smoking at follow-up. Among baseline past-30-day e-cigarette users, participants who used mods (versus vape pens) smoked >6 times as many cigarettes at follow-up (mean: 20.8 vs 1.3 cigarettes; rate ratio = 6.33; 95% confidence interval: 1.64-24.5) after adjustment for sociodemographic characteristics, baseline frequency of cigarette smoking, and number of days of e-cigarette use. After adjustment for device, neither nicotine e-liquid nor dripping were associated with frequency of cigarette smoking. Baseline mod users (versus vape pen users) smoked more cigarettes in the past 30 days at follow-up. Regulation of e-cigarette device type warrants consideration as a strategy to reduce cigarette smoking among adolescents and young adults who vape.

Impact of different fixed flow sampling protocols on flow-independent exhaled nitric oxide parameter estimates using the Bayesian dynamic two-compartment model.

Exhaled nitric oxide (FeNO) is an established respiratory biomarker with clinical applications in the diagnosis and management of asthma. Because FeNO depends strongly on the flow (exhalation) rate, early protocols specified that measurements should be taken when subjects exhaled at a fixed rate of 50 ml/s. Subsequently, multiple flow (or “extended”) protocols were introduced which measure FeNO across a range of fixed flow rates, allowing estimation of parameters including CawNO and CANO which partition the physiological sources of NO into proximal airway wall tissue and distal alveolar regions (respectively). A recently developed dynamic model of FeNO uses flow‐concentration data from the entire exhalation maneuver rather than plateau means, permitting estimation of CawNO and CANO from a wide variety of protocols. In this paper, we use a simulation study to compare CawNO and CANO estimation from a variety of fixed flow protocols, including: single maneuvers (30, 50,100, or 300 ml/s) and three established multiple maneuver protocols. We quantify the improved precision with multiple maneuvers and the importance of low flow maneuvers in estimating CawNO. We conclude by applying the dynamic model to FeNO data from 100 participants of the Southern California Children's Health Study, establishing the feasibility of using the dynamic method to reanalyze archived online FeNO data and extract new information on CawNO and CANO in situations where these estimates would have been impossible to obtain using traditional steady‐state two compartment model estimation methods.

Evaluating the predictive value of measures of susceptibility to tobacco and alternative tobacco products

BackgroundThe “cigarette susceptibility index” has been adapted for other products, yet, the validity of these adapted measures–particularly among youth who have used other tobacco products–has not been evaluated. MethodsWe used prospective data from the Southern California Children's Health Study to evaluate the association of questionnaire measures assessing susceptibility to e-cigarette, cigarette, hookah and cigar/cigarillo/little cigar use at wave 1 (W1; 11th/12th grade) with subsequent initiation between W1 and W2 (16 months later, N = 1453). We additionally examined whether each effect estimate differed by use of other tobacco products at W1. ResultsOdds ratios, attributable risk%, and risk differences for product initiation among susceptible vs. non-susceptible youth were consistently higher among never users of any tobacco product than among youth with any tobacco use history. For example, susceptible (vs. non-susceptible) youth with no prior tobacco use had 3.64 times the odds of subsequent initiation of e-cigarettes (95%CI:2.61,5.09), while among users of another product, susceptible (vs. non-susceptible) youth had 1.95 times the odds of e-cigarette initiation (95%CI:0.98,3.89; p-interaction = 0.016). 60.4% of e-cigarette initiation among never users of any product could be attributed to susceptibility, compared to 19.8% among users of another product. The e-cigarette absolute risk difference between susceptible and non-susceptible youth was 21.9%(15.2,28.6) for never users, vs. 15.4%(0.2,30.7) for users of another product. ConclusionTobacco product-specific susceptibility associations with initiation of use at W2 were markedly attenuated among prior users of other products, demonstrating reduced utility for these measures among subjects using other products.

Regional and traffic-related air pollutants are associated with higher consumption of fast food and trans fat among adolescents

Air pollution exposures are novel contributors to the growing childhood obesity epidemic. One possible mechanism linking air pollution exposures and obesity is through changes in food consumption patterns. The aim of this study was to examine the longitudinal association between childhood exposure to air pollutants and changes in diet among adolescents. School-age children were enrolled in the Southern California Children's Health Study during 1993-1994 (n=3100) and were followed for 4-8 y. Community-level regional air pollutants [e.g., nitrogen dioxide (NO2), elemental carbon (EC), and fine particles with aerodynamic diameter <2.5 µm (PM2.5)] were measured at central monitoring stations. Line dispersion modeling was used to estimate concentrations of traffic-related air pollutants based on nitrogen oxides (NOx) at participants' residential addresses. In addition, self-reported diet information was collected annually using a structured youth/adolescent food-frequency questionnaire during 1997-2001. Generalized linear mixed-effects models were used in the association analyses. Higher exposures to regional and traffic-related air pollutants were associated with intake of a high-trans-fat diet, after adjusting for confounders including socioeconomic status and access to fast food in the community. A 2-SD (12.2 parts per billion) increase in regional NO2 exposure was associated with a 34% increased risk of consuming a high-trans-fat diet compared with a low-trans-fat diet (OR: 1.34; 95% CI:1.05, 1.72). In addition, higher exposures to acid vapor, EC, PM2.5, and non-freeway NOx were all associated with higher consumption of dietary trans fat (all P<0.04). Notably, higher exposures to regional NO2, acid vapor, and EC were also associated with a higher consumption of fast food (all P<0.05). Childhood exposures to regional and traffic-related air pollutants were associated with increased consumption by adolescents of trans fat and fast foods. Our results indicate that air pollution exposures may contribute to obesogenic behaviors. This study was registered at clinicaltrials.gov as NCT03379298.

The impact of local regulation on reasons for electronic cigarette use among Southern California young adults

ObjectiveTobacco control policies have decreased tobacco use among youth and young adults. We aimed to identify whether specific local tobacco retail licensing ordinances were associated with reasons for e-cigarette use, in order to examine whether strong local policies may reduce e-cigarette initiation rates by influencing the appeal of these products. MethodsOnline questionnaires were completed by Southern California Children's Health Study participants in 2015–2016 (mean age = 18.9 years). Those who had ever used an e-cigarette (N = 614) were asked about reasons for use; additional data were collected on local jurisdiction tobacco sales policy, friends' attitudes toward e-cigarette use, e-cigarette characteristics (level of nicotine, flavorings), and history of tobacco use. Multivariate logistic regression models evaluated associations of each factor with reasons for e-cigarette use, adjusting for gender, ethnicity, highest parental education, tobacco use history and with a random effect of jurisdiction. ResultsThe top reason for e-cigarette use was “They come in flavors I like” (56.6%). Using e-cigarettes to quit smoking was uncommon (12.8%). Participants in jurisdictions with weaker tobacco retail licensing ordinances were more likely to report use of e-cigarettes because they are less harmful than cigarettes (50.1% vs. 36.2%), more acceptable to non-tobacco users (38% vs. 25%), and because they can use e-cigarettes in places where smoking is prohibited (30.7% vs. 18.3%; all p < .05). ConclusionTargeted policy to enforce a strong regulatory environment that denormalizes e-cigarette use, conveys the adverse impact of e-cigarettes, and restricts use in public places may reduce e-cigarette use among adolescents and young adults.

Estimation of the Effect of Hypothetical Air Pollution Scenarios on Lung Function in the Southern California Children's Health Study: An Application of G-Computation

Background: We have shown improved lung function with decreasing pollutant levels across several cohorts from the Southern Californian Children’s Health Study (CHS). In this study, we estimat...

RISK EFFECTS OF NEAR-ROADWAY POLLUTANTS AND ASTHMA STATUS ON BRONCHITIC SYMPTOMS IN CHILDREN.

Bronchitic symptoms in children pose a significant clinical and public health burden. Exposures to criteria air pollutants affect bronchitic symptoms, especially in children with asthma. Less is known about near-roadway exposures. Bronchitic symptoms (bronchitis, chronic cough, or phlegm) in the past 12 months were assessed annually with 8 to 9 years of follow-up on 6757 children from the southern California Children's Health Study. Residential exposure to freeway and non-freeway near-roadway air pollution was estimated using a line-source dispersion model. Mixed-effects logistic regression models were used to relate near-roadway air pollutant exposures to bronchitic symptoms among children with and without asthma. Among children with asthma, a two standard deviation increase in non-freeway exposures (odds ratio [OR]: 1.44; 95% confidence interval [CI]: 1.17-1.78) and freeway exposures (OR: 1.31; 95% CI: 1.06-1.60) were significantly associated with increased risk of bronchitic symptoms. Among children without asthma, only non-freeway exposures had a significant association (OR: 1.14; 95% CI: 1.00-1.29). Associations were strongest among children living in communities with lower regional particulate matter. Near-roadway air pollution was associated with bronchitic symptoms, especially among children with asthma and those living in communities with lower regional particulate matter. Better characterization of traffic pollutants from non-freeway roads is needed since many children live in close proximity to this source.

Bayesian estimation of physiological parameters governing a dynamic two-compartment model of exhaled nitric oxide.

The fractional concentration of nitric oxide in exhaled breath (fe NO) is a biomarker of airway inflammation with applications in clinical asthma management and environmental epidemiology. fe NO concentration depends on the expiratory flow rate. Standard fe NO is assessed at 50 mL/sec, but “extended NO analysis” uses fe NO measured at multiple different flow rates to estimate parameters quantifying proximal and distal sources of NO in the lower respiratory tract. Most approaches to modeling multiple flow fe NO assume the concentration of NO throughout the airway has achieved a “steady‐state.” In practice, this assumption demands that subjects maintain sustained flow rate exhalations, during which both fe NO and expiratory flow rate must remain constant, and the fe NO maneuver is summarized by the average fe NO concentration and average flow during a small interval. In this work, we drop the steady‐state assumption in the classic two‐compartment model. Instead, we have developed a new parameter estimation approach based on measuring and adjusting for a continuously varying flow rate over the entire fe NO maneuver. We have developed a Bayesian inference framework for the parameters of the partial differential equation underlying this model. Based on multiple flow fe NO data from the Southern California Children's Health Study, we use observed and simulated NO concentrations to demonstrate that our approach has reasonable computation time and is consistent with existing steady‐state approaches, while our inferences consistently offer greater precision than current methods.

Effects of Childhood Asthma on the Development of Obesity among School-aged Children.

Asthma and obesity often occur together in children. It is unknown whether asthma contributes to the childhood obesity epidemic. We aimed to investigate the effects of asthma and asthma medication use on the development of childhood obesity. The primary analysis was conducted among 2,171 nonobese children who were 5-8 years of age at study enrollment in the Southern California Children's Health Study (CHS) and were followed for up to 10 years. A replication analysis was performed in an independent sample of 2,684 CHS children followed from a mean age of 9.7 to 17.8 years. Height and weight were measured annually to classify children into normal, overweight, and obese categories. Asthma status was ascertained by parent- or self-reported physician-diagnosed asthma. Cox proportional hazards models were fitted to assess associations of asthma history with obesity incidence during follow-up. We found that children with a diagnosis of asthma at cohort entry were at 51% increased risk of developing obesity during childhood and adolescence compared with children without asthma at baseline (hazard ratio, 1.51; 95% confidence interval, 1.08-2.10) after adjusting for confounders. Use of asthma rescue medications at cohort entry reduced the risk of developing obesity (hazard ratio, 0.57; 95% confidence interval, 0.33-0.96). In addition, the significant association between a history of asthma and an increased risk of developing obesity was replicated in an independent CHS sample. Children with asthma may be at higher risk of obesity. Asthma rescue medication use appeared to reduce obesity risk independent of physical activity.

The E-cigarette Social Environment, E-cigarette Use, and Susceptibility to Cigarette Smoking

PurposeOne concern regarding the recent increase in adolescent e-cigarette use is the possibility that electronic (e-) cigarettes may be used by those who might not otherwise have used cigarettes, and that dual use, or transition to cigarette use alone, may follow. MethodsQuestionnaire data were obtained in 2014 from 11th/12th grade students attending schools in 12 communities included in the Southern California Children's Health Study. We evaluated the cross-sectional association between e-cigarette use, the social environment (family and friends' use and approval of e-cigarettes and cigarettes), and susceptibility to future cigarette use among never cigarette smokers (N = 1,694), using previously validated measures based on reported absence of a definitive commitment not to smoke. ResultsAmong adolescents who had never used cigarettes, 31.8% of past e-cigarette users and 34.6% of current (past 30-day) e-cigarette users indicated susceptibility to cigarette use, compared with 21.0% of never e-cigarette users. The odds of indicating susceptibility to cigarette use were two times higher for current e-cigarette users compared with never users (odds ratio = 1.97; 95% confidence interval: 1.21–3.22). A social environment favorable to e-cigarettes (friends' use of and positive attitudes toward the use of e-cigarettes) was also associated with greater likelihood of susceptibility to cigarette use, independent of an individual's e-cigarette use. ConclusionsE-cigarette use in adolescence, and a pro–e-cigarette social environment, may put adolescents at risk for future use of cigarettes. E-cigarettes may contribute to subsequent cigarette use via nicotine addiction or social normalization of smoking behaviors.

Patterns of Alternative Tobacco Product Use: Emergence of Hookah and E-cigarettes as Preferred Products Amongst Youth

PurposeThere is a growing public health concern related to the rapid increase in the use of multiple tobacco products among adolescents. This study examined patterns of adolescent use of cigarettes, e-cigarettes, cigars/cigarillo, hookah/waterpipe, and smokeless/dip/chewing tobacco in a population of southern California adolescents. MethodsData from 2,097 11th- and 12th-grade participants in the Southern California Children's Health Study were collected via self-report in 2014. Study participants were asked about lifetime and current (past 30 days) use of cigarettes, cigars/cigarillos/little cigars, e-cigarettes, hookah/waterpipe, and smokeless/dip/chewing tobacco. Latent class analysis (LCA) was used to identify patterns of tobacco use. ResultsHookah/waterpipe tobacco use had the highest current prevalence (10.7%) followed by e-cigarettes (9.6%). The prevalence of use of smokeless/dip/chewing tobacco was lowest, with 2.2% of adolescents reporting current use. The LCA suggested four distinct classes, comprising nonusers (72.3% of the sample), polytobacco experimenters (13.9%), e-cigarette/hookah users (8.2%), and polytobacco users (5.6%). Multinomial logistic regression based on these four classes found that males had double the odds to be polytobacco users relative to nonusers compared to females (odds ratio, 2.3; 95% confidence interval, 1.26–4.25). ConclusionsBy identifying naturally occurring configurations of tobacco product use in teens, these findings may be useful to practitioners and policymakers to identify the need for tobacco control interventions that address specific tobacco products and particular combinations of polytobacco use. LCA can be used to identify segments of the population overrepresented among certain tobacco use classes (e.g., boys) that may benefit most from targeted polyproduct intervention approaches.

Psychosocial Factors Associated With Adolescent Electronic Cigarette and Cigarette Use.

Use of electronic cigarettes (e-cigarettes) among adolescents has increased since their introduction into the US market in 2007. Little is known about the role of e-cigarette psychosocial factors on risk of e-cigarette or cigarette use in adolescence. Information on e-cigarette and cigarette psychosocial factors (use and attitudes about use in the home and among friends) was collected from 11th- and 12th-grade participants in the Southern California Children's Health Study during the spring of 2014. Of 2084 participants, 499 (24.0%) had used an e-cigarette, including 200 (9.6%) current users (past 30 days); 390 participants (18.7%) had smoked a combustible cigarette, and 119 (5.7%) were current cigarette smokers. Cigarette and e-cigarette use were correlated. Nevertheless, 40.5% (n = 81) of current e-cigarette users had never smoked a cigarette. Psychosocial factors (home use of each product, friends' use of and positive attitudes toward e-cigarettes and cigarettes) and participant perception of the harm of e-cigarettes were strongly positively associated both with e-cigarette and cigarette use. Most youth who reported e-cigarette use had friends who used e-cigarettes, and almost half of current users reported that they did not believe there were health risks associated with e-cigarette use. Longitudinal studies of adolescents are needed to determine whether the strong association of e-cigarette psychosocial factors with both e-cigarette and cigarette use will lead to increased cigarette use or dual use of cigarettes and e-cigarettes, or whether e-cigarettes will serve as a gateway to cigarette use.

Determinants of Children's Exhaled Nitric Oxide: New Insights from Quantile Regression.

While the fractional concentration of exhaled nitric oxide (FeNO) has proven useful in asthma research, its exact role in clinical care remains unclear, in part due to unexplained inter-subject heterogeneity. In this study, we assessed the hypothesis that the effects of determinants of the fractional concentration of exhaled nitric oxide (FeNO) vary with differing levels of FeNO. In a population-based cohort of 1542 school children aged 12–15 from the Southern California Children's Health Study, we used quantile regression to investigate if the relationships of asthma, socio-demographic and clinical covariates with FeNO vary across its distribution. Differences in FeNO between children with and without asthma increased steeply as FeNO increased (Estimated asthma effects (in ppb) at selected 20th, 50th and 80th percentiles of FeNO are 2.4, 6.3 and 22.2, respectively) but the difference was steeper with increasing FeNO in boys and in children with active rhinitis (p-values<0.01). Active rhinitis also showed significantly larger effects on FeNO at higher concentrations of FeNO (Estimated active rhinitis effects (in ppb) at selected 20th, 50th and 80th percentiles of FeNO are 2.1, 5.7 and 14.3, respectively). Boys and children of Asian descent had higher FeNO than girls and non-Hispanic whites; these differences were significantly larger in those with higher FeNO (p-values<0.01). In summary, application of quantile regression techniques provides new insights into the determinants of FeNO showing substantially varying effects in those with high versus low concentrations.

Chronic effects of air pollution on respiratory health in Southern California children: findings from the Southern California Children's Health Study.

Outdoor air pollution is one of the leading contributors to adverse respiratory health outcomes in urban areas around the world. Children are highly sensitive to the adverse effects of air pollution due to their rapidly growing lungs, incomplete immune and metabolic functions, patterns of ventilation and high levels of outdoor activity. The Children's Health Study (CHS) is a continuing series of longitudinal studies that first began in 1993 and has focused on demonstrating the chronic impacts of air pollution on respiratory illnesses from early childhood through adolescence. A large body of evidence from the CHS has documented that exposures to both regional ambient air and traffic-related pollutants are associated with increased asthma prevalence, new-onset asthma, risk of bronchitis and wheezing, deficits of lung function growth, and airway inflammation. These associations may be modulated by key genes involved in oxidative-nitrosative stress pathways via gene-environment interactions. Despite successful efforts to reduce pollution over the past 40 years, air pollution at the current levels still brings many challenges to public health. To further ameliorate adverse health effects attributable to air pollution, many more toxic pollutants may require regulation and control of motor vehicle emissions and other combustion sources may need to be strengthened. Individual interventions based on personal susceptibility may be needed to protect children's health while control measures are being implemented.