Impact of Smoking Ban on Passive Smoke Exposure in Pregnant Non-Smokers in the Southeastern United States

Tobacco Exposures are Associated With Healthcare Utilization and Healthcare Costs in Pregnant Persons and Their Newborn Babies

INTRODUCTION

Identifying healthcare utilization and costs associated with active and passive smoking during pregnancy could help improve health management strategies.

AIMS AND METHODS

Data are from the Newborn Epigenetics STudy (NEST), a birth cohort enrolled from 2005 to 2011 in Durham and adjacent counties in North Carolina, United States. Participants included those for whom prenatal serum samples were assayed and for whom administrative data were obtainable (N = 1045). Zero-inflated poisson regression models were used to assess associations between cotinine, adjusted for covariates (eg, race and ethnicity, age at delivery, cohabitation status, and education), and health care utilization outcomes. Generalized linear regression models were used to estimate average total charges. Simulation models were conducted to determine the economic benefits of reducing secondhand smoke and smoking during pregnancy.

RESULTS

Increasing levels of cotinine were positively associated with parent's number of emergency department (ED) visits (coefficient[b] = 0.0012, standard error [SE] = 0.0002; p < .001), the number of ICU hours (b = 0.0079, SE = 0.0025; p = .002), time spent in the ICU (b = 0.0238, SE = 0.0020, p < .001), and the number of OP visits (b = 0.0003, SE = 0.0001; p < .001). For infants, higher cotinine levels were associated with higher number of ED (b = 0.0012, SE = 0.0004; p = .005), ICU (b = 0.0050, SE = 0.001; p < .001), and OP (b = 0.0006, SE = 0.0002; p < .001) visits and longer time spent in the ED (b = 0.0025, SE = 0.0003; p < .001), ICU (b = 0.0005, SE = 0.0001; p < .001), and IP (b = 0.0020, SE = 0.0002; p < .001). Simulation results showed that a 5% reduction in smoking would correspond to a potential median cost savings of $150 533 from ED visits of parents and infants.

CONCLUSIONS

Our findings highlight the importance of smoke exposure cessation during pregnancy to reduce health care utilization and costs for both parents and infants.

IMPLICATIONS

This study reinforces the importance of reducing smoking and secondhand smoke exposure during pregnancy. Focusing on expanding cessation services to this group could help reduce morbidities observed within this population. Furthermore, there is the potential for healthcare cost savings to healthcare systems, especially for those with high delivery numbers. These cost savings are represented by potential reductions in ED, OP, and ICU hours and visits.

Promoting Smoke-Free Environments: The Impact of Thirdhand Smoke Awareness on Smoking Bans at Home

OBJECTIVE

A creating smoke-free home is a way to protect a vulnerable group from being exposed to secondhand smoke in the home, such as children, infants, and non-smokers. Studies reported an intervention for promoting a smoke-free home by using secondhand smoke messages and smoking cessation messages. However, the thirdhand smoke (THS) message has rarely been found. Therefore, this study aimed to explore the prevalence and correlations of smoking bans in homes.

METHODS

Secondary data from a community-based cross-sectional design survey was used for this study. Smoking ban status was defined as a smoking ban or no smoking ban. We used multiple logistic regression to test the association between factors and smoking ban status. An adjusted odd ratio and 95% confidence interval were reported.

RESULTS

Of the 882 participants included in this analysis, 38.66% (95%CI: 35.43, 41.97) had a smoking ban at home. A multiple logistic regression analysis showed that participants who believe that secondhand or THS harms children had a greater correlation with developing a smoking ban in the home compared with those who did not believe (odd ratio: 3.94, 95% confidence interval: 2.35, 6.60 and odd ratio:4.22, 95% confidence interval:2.6, 6.86, respectively).

CONCLUSION

This study found that the belief that thirdhand smoke and secondhand smoke exposure harm children. The smoke-free home message's relevance to the harms of thirdhand smoke exposure should be adapted to be promoted, especially in homes.

A Network Analysis of Multiple Preconception Health Behaviors in Chinese Women

BACKGROUND

A healthy preconception lifestyle, consisting of multiple health behaviors, is crucial for preventing adverse health outcomes in mothers and offspring. Although knowledge about the pattern of inter-behavior relations may provide insights for nudging multiple health behavior changes, this has not been adequately explored in the existing literature. Adopting a network perspective, the present study conceptualized multiple health behaviors as a behavior network (i.e., behaviors as nodes, inter-behavior relations as edges) and utilized network analysis to investigate the pattern of interrelations of preconception health behaviors in a large sample of Chinese women.

METHOD

We used the data of a population-based cohort study in China to estimate the behavior network. An analytic sample included 41,127 Chinese women who were surveyed about their adoptions of multiple health behaviors during the preconception period.

RESULTS

Network analysis revealed a relatively dense behavior network and visualized the network structure of multiple preconception health behaviors. Subsequent centrality analysis identified three central behaviors (i.e., avoiding second- or third-hand smoke, reducing psychosocial stress, and reducing alcohol) that had distinctively stronger connections to other behaviors.

CONCLUSIONS

Preconception health behaviors were strongly interconnected, and certain behaviors had stronger influences than others within the behavior network. Our findings highlight the strong inter-relatedness of preconception health behaviors. This study also encourages targeting the three central behaviors in preconception lifestyle promotions because this may bring more secondary improvements on other non-targeted behaviors and thereby achieve comprehensive lifestyle change.

Associations of Education and Income with Secondhand Smoke Exposure Among Non-smoking Pregnant Women in Japan: The Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study

OBJECTIVES

There is accumulating evidence that lower socioeconomic groups are more exposed to secondhand smoke (SHS) than higher ones in the general population. The objective of the study was to examine the associations of education and income with SHS exposure among non-smoking pregnant women in Japan.

METHODS

We analyzed data from 11,615 non-smoking pregnant women in Japan who participated in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study from 2013 to 2017. SHS exposure was defined as indoor exposure to someone else's cigarette smoke ≥ 1 day/week during pregnancy. Multiple logistic regression analyses were conducted to examine whether pregnant women's educational attainment or equivalent household income was associated with SHS exposure, adjusting for covariates. Stratified analyses by work status were also conducted.

RESULTS

The prevalence of SHS exposure during pregnancy was 32.6%; 27.6% among non-working women and 35.8% among working women. Lower educational attainment was associated with an increased risk of SHS exposure; the odds ratio of high school education or lower compared with university education or higher was 1.87 (95% confidence interval, 1.66-2.10). Lower equivalent household income was associated with an increased risk of SHS exposure; the odds ratio of the lowest compared with the highest level of income was 1.53 (95% confidence interval, 1.35-1.74). These associations did not differ between non-working women and working women.

CONCLUSIONS FOR PRACTICE

Associations of education and income with SHS exposure imply that educational interventions and financial incentives are needed for pregnant women and their household smokers.

The impact of an online educational program to reduce second-hand exposure to smoke among nonsmoking pregnant women; a hospital-based intervention study

Background

Second-hand smoke is recognized as a public health concern, especially for pregnant women.

Objectives

To compare pregnant women's exposure and perceptions of SHS pre-and post-intervention.

Materials and methods

The study was conducted with a sample of 32 pregnant women at a tertiary university hospital in Jordan. Using a semi-structured questionnaire, researchers asked women about their knowledge, attitude and behavior regarding prenatal exposure to smoke before and after an intervention that included motivation, communication, education and counselling by using a range of media. A cotinine test was conducted to measure levels in second-hand smokers.

Results

The average maternal age was 30.88 ± 1.69 years; 68% were highly educated, 43% were employed, 37% reported not having sufficient income, and 62% did not attend for antenatal care on a regular basis. There was a significant increase in knowledge and awareness regarding second-hand smoking and its effect on pregnancy outcomes after the intervention. More than 90% of pregnant women supported a comprehensive policy in relation to smoking, and 33% of used to leave the room where others smoked. This percentage increased to 70% after the intervention. Cotinine level decreased after the intervention in 81% of cases.

Conclusions

There is an increase in knowledge and awareness regarding second-hand smoking and its effects on pregnancy outcomes after implementation of an educational intervention.

Maternal tobacco smoke exposure is associated with increased DNA methylation at human metastable epialleles in infant cord blood

Metastable epialleles (MEs) are genomic regions that are stochastically methylated prior to germ layer specification and exhibit high interindividual but low intra-individual variability across tissues. ME methylation is vulnerable to environmental stressors, including diet. Tobacco smoke (TS) exposure during pregnancy is associated with adverse impacts on fetal health and maternal micronutrient levels as well as altered methylation. Our objective was to determine if maternal smoke exposure impacts methylation at MEs. Consistent with prior studies, we observed reductions in one-carbon pathway micronutrients with gestational TS exposure, including maternal folate (P = 0.02) and vitamins B6 (P = 0.05) and B12 (P = 0.007). We examined putative MEs BOLA3, PAX8, and ZFYVE28 in cord blood specimens from 85 Newborn Epigenetics STudy participants. Gestational TS exposure was associated with elevated DNA methylation at PAX8 (+5.22% average methylation; 95% CI: 0.33% to 10.10%; P = 0.037). In human conceptal kidney tissues, higher PAX8 transcription was associated with lower methylation (R s = 0.55; P = 0.07), suggesting that the methylation levels established at MEs, and their environmentally induced perturbation, may have meaningful, tissue-specific functional consequences. This may be particularly important because PAX8 is implicated in several cancers, including pediatric kidney cancer. Our data are the first to indicate vulnerability of human ME methylation establishment to TS exposure, with a general trend of increasing levels of methylation at these loci. Further investigation is needed to determine how TS exposure-mediated changes in DNA methylation at MEs, and consequent expression levels, might affect smoking-related disease risk.

Validation of differential DNA methylation in newborns exposed to tobacco smoke during gestation using bisulfite pyrosequencing

Maternal exposure to tobacco smoke during pregnancy has been associated with many negative child health outcomes. Tobacco smoke exposure alters DNA methylation in the developing embryo/fetus and may be a mechanism that increases risk of later life disease. Previous studies have identified CpG sites in umbilical cord blood that are associated with in utero tobacco smoke exposure. We sought to validate findings for CpG sites within several of the top hit genes, AHRR , CYP1A1 , and GFI1, using targeted quantitative bisulfite pyrosequencing. Comparing results from cord blood specimens of tobacco smoke-exposed to unexposed newborns, we confirmed significance at all previously identified CpG sites tested, including one in AHRR (p=0.007), three in CYP1A1 (p<0.0001), and one in GFI1 (p=0.008). These assays also captured novel differentially methylated CpGs located near the identified sites that were not included in the prior array-based studies (p value range, 0.02 to <0.0001). These results validate the prior findings and provide a simplified and more economical approach to analysis of CpG sites for expanded use as biomarkers of in utero tobacco smoke exposure.

Cotinine as an indicator of fetal exposure to active and passive smoking in pregnant women

Introduction

Within 5 years, the number of pregnant smokers in Poland decreased by 5%. Still, 6% of pregnant women are active and 18% are passive smokers, and 5% smoke and drink alcohol. The study examined the levels of cotinine concentration in the blood of pregnant women and in the umbilical cord blood of their children in relation to the number of cigarettes smoked; the places and persons conducive to exposure of pregnant women to tobacco smoke were determined.

Materials and Methods

The study included 123 women who have entered medical facilities for childbirth during physiological pregnancy, who filled out a questionnaire about their lifestyle. Moreover, venous and umbilical blood was collected from them and their newborns for cotinine evaluation. The nicotine marker was determined by the UPLC/MS/MS analytical method.

Results

When examining the frequency of smoking and exposure to smoke, it was found that 38% of the respondents concealed their smoking status by giving false answers, as shown by the biochemical analysis of the presence of cotinine in the blood. A significant correlation was found between the cotinine levels of exposed and smoking mothers and their babies. Pregnant smokers were in the presence of smokers more often (p = 0.019). Moreover, it was found that the presence of women in the company of smokers who smoked more than 20 cigarettes/day resulted in a significant (p = 0.011) increase of cotinine in the umbilical blood in 31.5% of newborns, higher than the concentration in mothers.

Conclusions

Protecting women from passive smoking requires extensive educational measures. The inclusion of cotinine level assessment in pregnant women in the program of the standard of perinatal examinations should be considered in order to protect children from diseases resulting from the effects of nicotine in the embryonic period.

Identifying the Best Questions for Rapid Screening of Secondhand Smoke Exposure Among Children

INTRODUCTION

Many children suffer from secondhand smoke exposure (SHSe), which leads to a variety of negative health consequences. However, there is no consensus on how clinicians can best query parents for possible SHSe among children. We employed a data-driven approach to create an efficient screening tool for clinicians to quickly and correctly identify children at risk for SHSe.

METHODS

Survey data from mothers and biospecimens from children were ascertained from the Neurodevelopment and Improving Children's Health following Environmental Tobacco Smoke Exposure (NICHES) study. Included were mothers and their children whose saliva were assayed for cotinine (n = 351 pairs, mean child age = 5.6 years). Elastic net regression predicting SHSe, as indicated from cotinine concentration, was conducted on available smoking-related questions and cross-validated with 2015-2016 National Health and Nutrition Examination Survey (NHANES) data to select the most predictive items of SHSe among children (n = 1670, mean child age = 8.4 years).

RESULTS

Answering positively to at least one of the two final items ("During the past 30 days, did you smoke cigarettes at all?" and "Has anyone, including yourself, smoked tobacco in your home in the past 7 days?") showed area under the curve = .82, and good specificity (.88) and sensitivity (.74). These results were validated with similar items in the nationally representative NHANES sample, area under the curve = .82, specificity = .78, and sensitivity = .77.

CONCLUSIONS

Our data-driven approach identified and validated two items that may be useful as a screening tool for a speedy and accurate assessment of SHSe among children.

IMPLICATIONS

The current study used a rigorous data-driven approach to identify questions that could reliably predict SHSe among children. Using saliva cotinine concentration levels as a gold standard for determining SHSe, our analysis employing elastic net regression identified two questions that served as good classifier for distinguishing children who might be at risk for SHSe. The two items that we validated in the current study can be readily used by clinicians, such as pediatricians, as part of screening procedures to quickly identify whether children might be at risk for SHSe.

Smoke-Free Home Rules and Association with Child Secondhand Smoke Exposure among Mother-Child Dyad Relationships

Smoke-free home rules restrict smoking in the home, but biomarkers of secondhand smoke exposure are needed to help understand the association between smoke-free homes and child secondhand smoke exposure. Participants (n = 346) were majority Black/African American mother-child dyads from a longitudinal study in North Carolina. Mothers completed questionnaires on household smoking behaviors and rules, and child saliva samples were assayed for secondhand smoke exposure. Regression models used smoke-free home rules to predict child risk for secondhand smoke exposure. Children in households with smoke-free home rules had less salivary cotinine and risk for secondhand smoke exposure. After controlling for smokers in the household, home smoking rules were not a significant predictor of secondhand smoke exposure. Compared to children in households with no smokers, children in households with at least one smoker but a non-smoking mother (OR 5.35, 95% CI: 2.22, 13.17) and households with at least one smoker including a smoking mother (OR 13.73, 95% CI: 6.06, 33.28) had greater risk for secondhand smoke exposure. Results suggest smoke-free home rules are not sufficient to fully protect children from secondhand smoke exposure, especially in homes with smokers. Future research should focus on how household members who smoke can facilitate the prevention of child secondhand smoke exposure.

DNA Methylation in Babies Born to Nonsmoking Mothers Exposed to Secondhand Smoke during Pregnancy: An Epigenome-Wide Association Study

BACKGROUND

Maternal smoking during pregnancy is related to altered DNA methylation in infant umbilical cord blood. The extent to which low levels of smoke exposure among nonsmoking pregnant women relates to offspring DNA methylation is unknown.

OBJECTIVE

This study sought to evaluate relationships between maternal prenatal plasma cotinine levels and DNA methylation in umbilical cord blood in newborns using the Infinium HumanMethylation 450K BeadChip.

METHODS

Participants from the Newborn Epigenetics Study cohort who reported not smoking during pregnancy had verified low levels of cotinine from maternal prenatal plasma (0 ng / mL to < 4  ng / mL ), and offspring epigenetic data from umbilical cord blood were included in this study (n = 79 ). Multivariable linear regression models were fit to the data, controlling for cell proportions, age, race, education, and parity. Estimates represent changes in response to any 1 -ng / mL unit increase in exposure.

RESULTS

Multivariable linear regression models yielded 29,049 CpGs that were differentially methylated in relation to increases in cotinine at a 5% false discovery rate. Top CpGs were within or near genes involved in neuronal functioning (PRKG1, DLGAP2, BSG), carcinogenesis (FHIT, HSPC157) and inflammation (AGER). Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggest cotinine was related to methylation of gene pathways controlling neuronal signaling, metabolic regulation, cell signaling and regulation, and cancer. Further, enhancers associated with transcription start sites were enriched in altered CpGs. Using an independent sample from the same study population (n = 115 ), bisulfite pyrosequencing was performed with infant cord blood DNA for two genes within our top 20 hits (AGER and PRKG1). Results from pyrosequencing replicated epigenome results for PRKG1 (cg17079497, estimate = - 1.09 , standard error  ( SE ) = 0.45 , p = 0.018 ) but not for AGER (cg09199225; estimate = - 0.16 , SE = 0.21 , p = 0.44 ).

DISCUSSION

Secondhand smoke exposure among nonsmoking women may alter DNA methylation in regions involved in development, carcinogenesis, and neuronal functioning. These novel findings suggest that even low levels of smoke exposure during pregnancy may be sufficient to alter DNA methylation in distinct sites of mixed umbilical cord blood leukocytes in pathways that are known to be altered in cord blood from pregnant active smokers. https://doi.org/10.1289/EHP8099.

An examination of social and environmental determinants of secondhand smoke exposure among non-smoking adolescents

INTRODUCTION

Adolescents are at increased risk of secondhand smoke exposure (SHS) due to the limited control that they have over social and physical environments. Yet, knowledge regarding determinants of SHS among non-smoking adolescents is limited. This study identifies social and environmental factors associated with SHS among non-smoking adolescents.

METHODS

To be included, parents and adolescents (aged 11–17 years) of the Adolescents, Place, and Behavior Study had to have completed surveys between March 2019 and May 2020. Adolescents had to have not reported smoking within the past 30 days and provided a saliva sample assayed for cotinine (≤3 ng/mL). A series of stepwise linear regression models were fit to the data to identify social and environmental determinants of SHS, using log-transformed salivary cotinine.

RESULTS

Of the 105 adolescent and parent dyads included, 90.3% were African American, 26.9% of parents reported smoking, 33.3% resided in multi-unit housing, and 67.7% lived in homes where smoking was not permitted. Significant associations were found between parent tobacco use (β=2.56, SE=0.98, p=0.0082) and residing in multi-unit housing (β=1.72, SE=0.86, p=0.0460) with increased log-transformed cotinine levels among non-smoking adolescents. Adolescent age, gender, and race/ ethnicity, parental education, peer tobacco use, the number of adults and children in the home, average number of days of self-reported SHS within public spaces outside of the home, and home smoking policies were not significantly associated with cotinine.

CONCLUSIONS

Results emphasize the importance of reducing secondhand smoke exposure by reducing parental smoking and altering exposures within social and home environments. Parental tobacco use and residential setting should be considered when developing interventions to reduce secondhand smoke exposure among non-smoking adolescents.

Impact of population tobacco control interventions on socioeconomic inequalities in smoking: a systematic review and appraisal of future research directions

BACKGROUND

While price increases and targeted cessation support have been found to reduce inequalities in smoking by socioeconomic status (SES), evidence on other measures is mixed. We aimed to update the most recent (2014) previous review by identifying and appraising evidence published since 2013 on the equity impact of population tobacco control measures.

METHODS

Systematic searching of 10 electronic databases and hand-searching of four key journals identified 68 primary research articles published since 2013 that sought to examine the equity impact of population tobacco control measures in high-income countries with a negative socioeconomic gradient in smoking. Reported equity impacts were categorised as positive (greater impact among lower SES), neutral (no difference by SES), negative (greater impact among higher SES) or mixed/unclear.

RESULTS

There was substantial growth in research seeking to evaluate the equity impact of tobacco control interventions, but the majority of new studies showed mixed/unclear results. Findings for price increases and targeted cessation support continue to suggest an equity-positive impact, but limitations in the available evidence make further assessment difficult. Substantial differences in the context, scale and implementation of tobacco control policies make straightforward comparison of findings from the previous 2014 and current reviews problematic.

CONCLUSION

Researchers need to adopt more sophisticated, multidisciplinary approaches in evaluating the equity impact of tobacco control measures-developing robust measures of equity effect and using frameworks that take account of context, existing systems/processes and the likely mechanisms of action. Socioeconomic differences in intervention impact within low-income and middle-income countries require evaluation.

Effect of Prenatal Smoke Exposure on Birth Weight: The Moderating Role of Maternal Depressive Symptoms

INTRODUCTION

Both prenatal smoke exposure and depression have been linked to lower birth weight, a risk factor for morbidity and mortality. Few studies have looked at the interaction between these risk factors and none have used a biomarker to objectively measure prenatal smoke exposure. The current study sought to examine independent and interactive effects of cotinine and depression on birth weight. The effect of race was also explored.

METHOD

Data were drawn from a prospective study of pregnant women (N = 568) in the southeastern United States. Maternal demographic, health information, depressive symptoms, and birth data were collected via self-report and medical record abstraction. Prenatal blood samples were assayed for cotinine.

RESULTS

Controlling for covariates, multiple regression analyses indicated that both cotinine and depressive symptoms independently predicted lower birth weight and a significant interaction was also observed. Upon probing the interaction, a negative association between cotinine levels and birth weight was found in the context of higher depression but not lower depression scores. Similarly, logistic regression analyses revealed a significant interaction between cotinine and depression, such that cotinine predicted having a baby less than 2500 g among women who fell above the indicated cutoff score. African American women had the highest levels of cotinine and lowest weight babies; however, race was not a significant moderator.

CONCLUSIONS

Results suggest prenatal smoke exposure has a greater negative effect on birth weight for women endorsing co-occurring depressive symptoms. Findings can inform targeted interventions and assist medical providers with identifying women at increased risk for poor perinatal outcomes.

IMPLICATIONS

Despite the common occurrence of smoking during pregnancy and prenatal depression, the interaction between these risk factors on birth weight has rarely been examined. Further, the extant results have been mixed, likely due in part to difficulties in measurement. The current study was the first to use prenatal cotinine to assess bias-free, continuous levels of prenatal smoke exposure. Results indicate that prenatal cotinine was a significant predictor of birth weight only in the context of maternal depressive symptoms. These findings have important implications for mitigating negative perinatal outcomes for pregnant women and their children.

Partial Smoking Ban and Secondhand Smoke Exposure in Japan

Implementing smoking bans is a worldwide common practice for tobacco control. However, if the policy prohibits smoking partially rather than comprehensively, it may increase nonsmokers’ exposure to secondhand smoke (SHS) in nonprohibited places. This paper investigates how a partial smoking ban affected nonsmokers’ SHS exposure (measured by frequency of having exposure to SHS in days per month) in households, workplaces, and restaurants by examining the case of a partial smoking ban introduced in a large Japanese prefecture in 2013. Using data from the National Health and Nutrition Survey (NHNS) in 2010, 2013, and 2016 (n = 30,244) and the Comprehensive Survey of Living Conditions (CSLC) from 2001 to 2016 (n = 2,366,896), this paper employs a difference-in-differences (DID) approach. We found that the partial smoking ban significantly increased their SHS exposure in households and workplaces by 2.64 days and 4.70 days per month, respectively, while it did not change nonsmokers’ SHS exposure in restaurants. The results imply that the smoking ban displaced smokers from public places to private places. We also found that neither smokers’ smoking status nor smoking intensity changed significantly after implementing the partial smoking ban. Comprehensive smoking bans are needed to better protect nonsmokers from SHS exposure.

Social determinants of smoke exposure during pregnancy: Findings from waves 1 & 2 of the Population Assessment of Tobacco and Health (PATH) Study

Maternal smoking during pregnancy (MSDP) and secondhand smoke (SHS) exposure are associated with a myriad of negative health effects for both mother and child. However, less is known regarding social determinants for SHS exposure, which may differ from those of maternal smoking during pregnancy (MSDP). To identify social determinants for SHS exposure only, MSDP only, and MSDP and SHS exposure, data were obtained from all pregnant women (18-54 years; N = 726) in waves 1 and 2 of the Population Assessment of Tobacco and Health Study (2014-2015). Multiple logistic regressions were conducted using SAS 9.4. Smoke exposure during pregnancy was common; 23.0% reported SHS exposure only, 6.1% reported MSDP only, and 11.8% reported both SHS exposure and MSDP. Results demonstrate that relationships between smoke exposure during pregnancy and social determinants vary by type of exposure. Women at risk for any smoke exposure during pregnancy include those who are unmarried and allow the use of combustible tobacco products within the home. Those who are at higher risk for SHS exposure include those who are younger in age, and those who are earlier in their pregnancy. Those who are at higher risk for maternal smoking include those with fair/poor mental health status and those who believe that others' view tobacco use more positively. These results suggest the need for implementing more comprehensive policies that promote smoke-free environments. Implementing these strategies have the potential to improve maternal and fetal health outcomes associated with tobacco smoke exposure.

Self-reported prenatal tobacco smoke exposure, AXL gene-body methylation, and childhood asthma phenotypes

BACKGROUND

Epigenetic modifications, including DNA methylation, act as one potential mechanism underlying the detrimental effects associated with prenatal tobacco smoke (PTS) exposure. Methylation in a gene called AXL was previously reported to differ in response to PTS.

METHODS

We investigated the association between PTS and epigenetic changes in AXL and how this was related to childhood asthma phenotypes. We tested the association between PTS and DNA methylation at multiple CpG loci of AXL at birth using Pyrosequencing in two separate study populations, the Children's Health Study (CHS, n = 799) and the Newborn Epigenetic Study (NEST, n = 592). Plasma cotinine concentration was used to validate findings with self-reported smoking status. The inter-relationships among AXL mRNA and miR-199a1 expression, PTS, and AXL methylation were examined. Lastly, we evaluated the joint effects of AXL methylation and PTS on the risk of asthma and related symptoms at age 10 years old.

RESULTS

PTS was associated with higher methylation level in the AXL gene body in both CHS and NEST subjects. In the pooled analysis, exposed subjects had a 0.51% higher methylation level in this region compared to unexposed subjects (95% CI 0.29, 0.74; p < 0.0001). PTS was also associated with 21.2% lower expression of miR-199a1 (95% CI - 37.9, - 0.1; p = 0.05), a microRNA known to regulate AXL expression. Furthermore, the combination of higher AXL methylation and PTS exposure at birth increased the risk of recent episodes of bronchitic symptoms in childhood.

CONCLUSIONS

PTS was associated with methylation level of AXL and the combination altered the risk of childhood bronchitic symptoms.