The association between maternal smoking and secondhand exposure and autonomic functioning at 2-4 weeks of age

Neonatal heart rate variability: a contemporary scoping review of analysis methods and clinical applications

BACKGROUND

Neonatal heart rate variability (HRV) is widely used as a research tool. However, HRV calculation methods are highly variable making it difficult for comparisons between studies.

OBJECTIVES

To describe the different types of investigations where neonatal HRV was used, study characteristics, and types of analyses performed.

ELIGIBILITY CRITERIA

Human neonates ≤1 month of corrected age.

SOURCES OF EVIDENCE

A protocol and search strategy of the literature was developed in collaboration with the McGill University Health Center's librarians and articles were obtained from searches in the Biosis, Cochrane, Embase, Medline and Web of Science databases published between 1 January 2000 and 1 July 2020.

CHARTING METHODS

A single reviewer screened for eligibility and data were extracted from the included articles. Information collected included the study characteristics and population, type of HRV analysis used (time domain, frequency domain, non-linear, heart rate characteristics (HRC) parameters) and clinical applications (physiological and pathological conditions, responses to various stimuli and outcome prediction).

RESULTS

Of the 286 articles included, 171 (60%) were small single centre studies (sample size <50) performed on term infants (n=136). There were 138 different types of investigations reported: physiological investigations (n=162), responses to various stimuli (n=136), pathological conditions (n=109) and outcome predictor (n=30). Frequency domain analyses were used in 210 articles (73%), followed by time domain (n=139), non-linear methods (n=74) or HRC analyses (n=25). Additionally, over 60 different measures of HRV were reported; in the frequency domain analyses alone there were 29 different ranges used for the low frequency band and 46 for the high frequency band.

CONCLUSIONS

Neonatal HRV has been used in diverse types of investigations with significant lack of consistency in analysis methods applied. Specific guidelines for HRV analyses in neonates are needed to allow for comparisons between studies.

Prenatal nicotine exposure was associated with long-term impact on the cardiovascular system and regulation-Review

AIM

The aim of this structured review was to discuss knowledge of nicotine use during pregnancy and long-term effects on children's cardiovascular function.

METHODS

PubMed and MEDLINE were searched for original papers that covered various forms of nicotine exposure during pregnancy and this identified 314 papers published in English from inception of the databases to 1 March 2021. The research focus was prenatal exposure that had long-term effects on the cardiovascular system. The search was expanded from the reference list of the selected papers, which identified another 17 papers.

RESULTS

The 34 original papers that were included covered 172,696 subjects from foetuses to 19 years of age. Cardiovascular autonomic dysfunction was discussed in 12 of the papers and 16 studies reported on blood pressure. The remaining studies covered structural or functional changes in arterial wall or heart. There were convincing data on autonomic dysfunction and increased blood pressure. Some data were conflicting and problems with misclassification of exposure were evident.

CONCLUSION

Prenatal nicotine exposure was associated with long-term developmental changes in the cardiovascular system and regulation. There were no safe periods, doses or nicotine products during pregnancy and women should abstain when planning a pregnancy.

Exposures influencing the developing central autonomic nervous system

Autonomic nervous system function is critical for transition from in-utero to ex-utero life and is associated with neurodevelopmental and neuropsychiatric outcomes later in life. Adverse prenatal and neonatal conditions and exposures can impair or alter ANS development and, as a result, may also impact long-term neurodevelopmental outcomes. The objective of this article is to provide a broad overview of the impact of factors that are known to influence autonomic development during the fetal and early neonatal period, including maternal mood and stress during and after pregnancy, fetal growth restriction, congenital heart disease, toxic exposures, and preterm birth. We touch briefly on the typical development of the ANS, then delve into both in-utero and ex-utero maternal and fetal factors that may impact developmental trajectory of the ANS and, thus, have implications in transition and in long-term developmental outcomes. While many types of exposures and conditions have been shown to impact development of the autonomic nervous system, there is still much to be learned about the mechanisms underlying these influences. In the future, more advanced neuromonitoring tools will be required to better understand autonomic development and its influence on long-term neurodevelopmental and neuropsychological function, especially during the fetal period.

Autonomic functioning among cocaine-exposed kindergarten-aged children: Examination of child sex and caregiving environmental risk as potential moderators

The purpose of this study was to examine the hypothesis that child sex moderates the association between prenatal cocaine exposure (PCE) and autonomic functioning as well as to examine the role that caregiving environmental risk played in sex differences in autonomic functioning among exposed children. Measures of the parasympathetic nervous system (indexed by respiratory sinus arrhythmia [RSA]) and the sympathetic nervous system (indexed by skin conductance level [SCL]) were obtained from 146 (75 cocaine-exposed, 38 male; and 71 nonexposed, 36 male) children during baseline and a task designed to elicit negative affect (NA). We also examined the role of caregiving environmental risk as a moderator of the association between PCE and autonomic functioning separately for boys and girls. PCE boys had a significantly higher baseline RSA and lower baseline SCL than PCE girls or nonexposed children. Environmental risk also moderated the association between PCE and baseline RSA for boys, but not girls, such that boys with PCE and high environmental risk had the highest baseline RSA. These findings indicate that exposed boys had significantly lower levels of sympathetic activation while at rest. However, for autonomic reactivity, the exposed girls had a larger change in both RSA and SCL relative to nonexposed girls while exposed boys had significantly smaller increases in SCL during environmental challenge. Finally, girls with both PCE and high environmental risk had the highest levels of parasympathetic reactivity during challenge. These results underscore the importance of examining sex differences and considering comorbid environmental risk factors when examining developmental outcomes in cocaine-exposed children and highlight the complexity involved with understanding individual differences in cocaine-exposed populations.

Heart rate variability for determining autonomic nervous system effects of lifestyle behaviors in early life: A systematic review

BACKGROUND

An unhealthy lifestyle negatively alters autonomic nervous system (ANS) activity as reflected by decreased heart rate variability (HRV), increasing cardiovascular disease (CVD) risk. Research investigating the effect of modifiable lifestyle factors on ANS activity in young children is limited. Early identification of these risk factors is vital to improving long-term individual and public health outcomes. A systematic review was conducted to assess the effect of maternal or child modifiable lifestyle factors on child ANS activity.

METHODS

Following the 2009 PRISMA guidelines, three electronic databases were searched from February 2018 - July 2019 for articles describing human trials between 1996 - 2019. Included studies examined ANS activity of children between 28 weeks gestational age - 6 years in relation to modifiable lifestyle CVD risk factors.

RESULTS

Twenty-six studies fulfilled inclusion criteria. Sixteen studies reported that modifiable lifestyle factors significantly influenced the HRV of children. Increased HRV was significantly associated with higher maternal zinc and omega-3 fatty acid intake, regular maternal aerobic exercise and a non-smoking environment. Child diet and body composition demonstrated some support for an association between these modifiable lifestyle factors and child HRV.

CONCLUSION

There is cross-sectional evidence supporting an association between maternal lifestyle factors and child HRV. Evidence is less supportive of a relationship between child modifiable lifestyle factors and child HRV. Monitoring the effects of lifestyle interventions on the ANS via HRV measurements of both mother and child may identify child CVD risk.

Prenatal exposure to tobacco and marijuana and child autonomic regulation and reactivity: An analysis of indirect pathways via maternal psychopathology and parenting

We examined a conceptual model for the associations of prenatal exposure to tobacco (PTE) and marijuana with child reactivity/regulation at 16 months of age. We hypothesized that PTE would be associated with autonomic reactivity and regulation that these associations would be indirect via maternal anger/hostility, depression/stress, or harsh parenting assessed at 2 months and that these effects would be most pronounced among children exposed to both tobacco and marijuana (PTME). Participants were 247 dyads (81 PTE, 97 PTME, and 69 nonexposed) who were followed up at 2 (N = 247) and 16 months (N = 238) of child age. Results from model testing indicated an indirect association between PTME and autonomic functioning during the second year of life, which was mediated by harsh parenting during caregiver-infant interactions. This study fills an important gap in the literature on PTE, PTME, and autonomic regulation during the toddler years, highlighting the role of maternal parenting as important intervening variables.

An examination of the association between prenatal cocaine exposure and brain activation measures of arousal and attention in young adults: An fMRI study using the Attention Network Task

Prenatal drug exposure, including cocaine, alcohol, marijuana, and tobacco, is associated with deficits in behavioral regulation and attention. Using fMRI, the objective of this study was to characterize the association between prenatal cocaine exposure (PCE) and the underlying neural substrates associated with behavioral outcomes of attention. Forty-seven young adults were recruited for this study from the ongoing Maternal Health Practices and Child Development (MHPCD) Project, a longitudinal study of the effects of PCE on growth, behavior, and cognitive function. Three groups were compared: 1) prenatal exposure to cocaine, alcohol, marijuana, and tobacco (CAMT, n = 15), 2) prenatal exposure to alcohol, marijuana, and tobacco (AMT, n = 17), and 3) no prenatal exposure to drugs (Controls, n = 15). Subjects were frequency matched on gender, race, handedness, and 15-year IQ. This study used the theoretical model proposed by Posner and Peterson (1990), which posits three dissociable components of attention: alerting, orienting, and executive attention. Subjects completed a functional MRI (fMRI) scan while performing the Attention Network Task, a validated neuroimaging measure of the 3-network model of attention. Behavioral and fMRI data revealed no associations between PCE and task accuracy, speed of processing, or activation in key brain regions associated with each of the attention networks. The results of this study show that any subtle differences in brain function associated with PCE are not detectable using the ANT task and fMRI. These results should be interpreted in the context of other studies that have found associations between PCE and arousal with emotionally arousing stimuli, compared to this study that found no associations using emotionally neutral stimuli.

Prenatal exposure to tobacco and cannabis: Effects on autonomic and emotion regulation

Tobacco and cannabis are often used together in pregnancy and both have effects on children's regulatory system. Yet, little is known about the impact of co-use on the development of emotion regulation at the developmentally salient age of 2 years. One pathway linking co-exposure to tobacco and cannabis to toddler regulation may be via poor autonomic regulation in infancy. In addition, substance using mothers may be more dysregulated themselves, which may have direct effects on toddler regulation, but may also affect parenting, particularly maternal sensitivity during mother-child interactions. Thus, a second pathway linking exposure to toddler regulation may be via maternal dysregulation and low maternal sensitivity. We examined a conceptual model linking prenatal exposure to toddler regulation via these two pathways in a prospective sample (N = 247) of mother-child dyads recruited in the first trimester of pregnancy. Results indicated significant effects of co-exposure on poor autonomic regulation in infancy, which in turn predicted poor toddler emotion regulation. Mothers who used both tobacco and cannabis displayed lower sensitivity during play interactions with their infants. Maternal sensitivity was modestly stable from infant to toddler period and was predictive of higher toddler emotion regulation. Continued postnatal exposure to tobacco was also a significant, unique predictor of lower toddler emotion regulation. Results highlight the importance of examining co-exposure effects and suggest that this common pattern of use may be associated with higher infant/toddler risks.

Environmental tobacco smoke exposure and risk of habitual snoring in children: a meta-analysis

BACKGROUND

The association between environmental tobacco smoke (ETS) exposure and habitual snoring (HS) risk in children remains controversial. Therefore, a meta-analysis was carried out to evaluate and compare the effect of ETS by different family members and prenatal smoke exposure on the risk of HS in children.

METHODS

Relevant studies published in English were identified by a search of PubMed, Embase and Web of Science up to December 2017. Random effect model and fixed effect model were used to pool the findings. Restricted cubic splines were used to assess the dose-response relationship.

RESULTS

A total of 24 studies with 87 829 participants were included in the present meta-analysis. When comparing ETS exposed with non-ETS exposed, the pooled OR of HS were 1.46 (95% CI, 1.29 to 1.65) for household smoking exposure, 1.45 (95% CI, 1.27 to 1.65) for paternal smoking exposure, 1.87 (95% CI, 1.56 to 2.23) for maternal smoking exposure and 1.95 (95% CI, 1.63 to 2.34) for prenatal tobacco smoke exposure. For dose-response analysis, evidence of a linear association was found between household smoking exposure and HS, and the risk of HS increased by 2.1% (OR=1.02, 95% CI, 1.00 to 1.04, p=0.022) for every 1 cigarette/day increment of smoking by people living with children.

CONCLUSIONS

This meta-analysis of observational studies indicates that exposure to ETS, in particularly prenatal tobacco smoke exposure and maternal smoking, is associated with an increased risk of HS.

Assessment of tobacco smoke effects on neonatal cardiorespiratory control using a semi-automated processing approach

A semi-automated processing approach was developed to assess the effects of early postnatal environmental tobacco smoke (ETS) on the cardiorespiratory control of newborn lambs. The system consists of several steps beginning with artifact rejection, followed by the selection of stationary segments, and ending with feature extraction. This approach was used in six lambs exposed to 20 cigarettes/day for the first 15 days of life, while another six control lambs were exposed to room air. On postnatal day 16, electrocardiograph and respiratory signals were obtained from a 6-h polysomnographic recording. The effects of postnatal ETS exposure on heart rate variability, respiratory rate variability, and cardiorespiratory interrelations were explored. The unique results suggest that early postnatal ETS exposure increases respiratory rate variability and decreases the coupling between cardiac and respiratory systems. Potentially harmful consequences in early life include unstable breathing and decreased adaptability of cardiorespiratory function, particularly during early life challenges, such as prematurity or viral infection. Graphical abstract ᅟ.

Prenatal Risk and Infant Regulation: Indirect Pathways via Fetal Growth and Maternal Prenatal Stress and Anger

Pathways from maternal tobacco, marijuana, stress, and anger in pregnancy to infant reactivity and regulation (RR) at 9 months of infant age were examined in a low-income, diverse sample beginning in the first trimester of pregnancy, with fetal growth and postnatal stress/anger as potential mediators, and infant sex as a moderator. Participants were 247 dyads (173 substance-exposed infants). There were no direct effects of prenatal risk on RR and no moderation by sex. However, there were significant indirect effects on RR via poor fetal growth and higher postnatal anger. The study adds to the sparse literature on joint effects of tobacco and marijuana, and highlights the role of fetal growth and maternal anger as important pathways from prenatal risk to infant RR.

Cardiovascular Consequences of Childhood Secondhand Tobacco Smoke Exposure: Prevailing Evidence, Burden, and Racial and Socioeconomic Disparities: A Scientific Statement From the American Heart Association

BACKGROUND

Although public health programs have led to a substantial decrease in the prevalence of tobacco smoking, the adverse health effects of tobacco smoke exposure are by no means a thing of the past. In the United States, 4 of 10 school-aged children and 1 of 3 adolescents are involuntarily exposed to secondhand tobacco smoke (SHS), with children of minority ethnic backgrounds and those living in low-socioeconomic-status households being disproportionately affected (68% and 43%, respectively). Children are particularly vulnerable, with little control over home and social environment, and lack the understanding, agency, and ability to avoid SHS exposure on their own volition; they also have physiological or behavioral characteristics that render them especially susceptible to effects of SHS. Side-stream smoke (the smoke emanating from the burning end of the cigarette), a major component of SHS, contains a higher concentration of some toxins than mainstream smoke (inhaled by the smoker directly), making SHS potentially as dangerous as or even more dangerous than direct smoking. Compelling animal and human evidence shows that SHS exposure during childhood is detrimental to arterial function and structure, resulting in premature atherosclerosis and its cardiovascular consequences. Childhood SHS exposure is also related to impaired cardiac autonomic function and changes in heart rate variability. In addition, childhood SHS exposure is associated with clustering of cardiometabolic risk factors such as obesity, dyslipidemia, and insulin resistance. Individualized interventions to reduce childhood exposure to SHS are shown to be at least modestly effective, as are broader-based policy initiatives such as community smoking bans and increased taxation.

PURPOSE

The purpose of this statement is to summarize the available evidence on the cardiovascular health consequences of childhood SHS exposure; this will support ongoing efforts to further reduce and eliminate SHS exposure in this vulnerable population. This statement reviews relevant data from epidemiological studies, laboratory-based experiments, and controlled behavioral trials concerning SHS and cardiovascular disease risk in children. Information on the effects of SHS exposure on the cardiovascular system in animal and pediatric studies, including vascular disruption and platelet activation, oxidation and inflammation, endothelial dysfunction, increased vascular stiffness, changes in vascular structure, and autonomic dysfunction, is examined.

CONCLUSIONS

The epidemiological, observational, and experimental evidence accumulated to date demonstrates the detrimental cardiovascular consequences of SHS exposure in children.

IMPLICATIONS

Increased awareness of the adverse, lifetime cardiovascular consequences of childhood SHS may facilitate the development of innovative individual, family-centered, and community health interventions to reduce and ideally eliminate SHS exposure in the vulnerable pediatric population. This evidence calls for a robust public health policy that embraces zero tolerance of childhood SHS exposure.

Physiological reactivity during object manipulation among cigarette-exposed infants at 9 months of age

The purpose of this study was to examine the association between prenatal exposure to cigarettes and heart rate during an object manipulation task at 9 months of age. Second-by-second heart rate was recorded for 181 infants who were prenatally exposed to cigarettes and 77 nonexposed infants during the manipulation of four standardized toys. A series of longitudinal multilevel models were run to examine the association of prenatal smoking on the intercept and slope of heart rate during four 90-second object manipulation tasks. After controlling for maternal age, prenatal marijuana and alcohol use, duration of focused attention and activity level, results indicated that the heart rates of exposed infants significantly increased during the object manipulation task. These findings suggest casual rather than focused attention and a possible increase in physiological arousal during object manipulation.

Predictors of obstructive sleep apnea severity in adenotonsillectomy candidates

STUDY OBJECTIVES

There is uncertainty over which characteristics increase obstructive sleep apnea syndrome (OSAS) severity in children. In candidates for adenotonsillectomy (AT), we evaluated the relationship of OSAS severity and age, sex, race, body mass index (BMI), environmental tobacco smoke (ETS), prematurity, socioeconomic variables, and comorbidities.

DESIGN

Cross-sectional screening and baseline data were analyzed from the Childhood Adenotonsillectomy Trial, a randomized, controlled, multicenter study evaluating AT versus medical management. Regression analysis assessed the relationship between the apnea hypopnea index (AHI) and risk factors obtained by direct measurement or questionnaire.

SETTING

Clinical referral setting.

PARTICIPANTS

Children, ages 5 to 9.9 y with OSAS.

MEASUREMENTS AND RESULTS

Of the 1,244 children undergoing screening polysomnography, 464 (37%) were eligible (2 ≤ AHI < 30 or 1 ≤ obstructive apnea index [OAI] < 20 and without severe oxygen desaturation) and randomized; 129 (10%) were eligible but were not randomized; 608 (49%) had AHI/OAI levels below entry criteria; and 43 (3%) had levels of OSAS that exceeded entry criteria. Among the randomized children, univariate analyses showed significant associations of AHI with race, BMI z score, environmental tobacco smoke (ETS), family income, and referral source, but not with other variables. After adjusting for potential confounders, African American race (P = 0.003) and ETS (P = 0.026) were each associated with an approximately 20% increase in AHI. After adjusting for these factors, obesity and other factors were not significant.

CONCLUSIONS

Apnea hypopnea index level was significantly associated with race and environmental tobacco smoke, highlighting the potential effect of environmental factors, and possibly genetic factors, on pediatric obstructive sleep apnea syndrome severity. Efforts to reduce environmental tobacco smoke exposure may help reduce obstructive sleep apnea syndrome severity.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov (#NCT00560859).

Programming of respiratory health in childhood: influence of outdoor air pollution

PURPOSE OF REVIEW

This overview highlights recent experimental and epidemiological evidence for the programming effects of outdoor air pollution exposures during early development on lung function and chronic respiratory disorders, such as asthma and related allergic disorders.

RECENT FINDINGS

Air pollutants may impact anatomy and/or physiological functioning of the lung and interrelated systems. Programming effects may result from pollutant-induced shifts in a number of molecular, cellular, and physiological states and their interacting systems. Specific key regulatory systems susceptible to programming may influence lung development and vulnerability to respiratory diseases, including both central and peripheral components of neuroendocrine pathways and autonomic nervous system (ANS) functioning which, in turn, influence the immune system. Starting in utero, environmental factors, including air pollutants, may permanently organize these systems toward trajectories of enhanced pediatric (e.g., asthma, allergy) as well as adult disease risk (e.g., chronic obstructive pulmonary disease). Evidence supports a central role of oxidative stress in the toxic effects of air pollution. Additional research suggests xenobiotic metabolism and subcellular components, such as mitochondria are targets of ambient air pollution and play a role in asthma and allergy programming. Mechanisms operating at the level of the placenta are being elucidated. Epigenetic mechanisms may be at the roots of adaptive developmental programming.

SUMMARY

Optimal coordinated functioning of many complex processes and their networks of interaction are necessary for normal lung development and the maintenance of respiratory health. Outdoor air pollution may play an important role in early programming of respiratory health and is potentially amenable to intervention.

Physiological Regulation at 9 Months of Age in Infants Prenatally Exposed to Cigarettes

The primary purpose of this study was to examine the association between prenatal cigarette exposure and physiological regulation at 9 months of age. Specifically, we explored the possibility that any association between prenatal cigarette exposure and infant physiological regulation was moderated by postnatal environmental tobacco smoke (ETS) exposure or infant gender. We evaluated whether male infants with prenatal cigarette exposure or infants who were also exposed to ETS after birth had the highest levels of physiological dysregulation. Respiratory sinus arrhythmia (RSA) was obtained from 206 (142 exposed and 64 nonexposed) infants during a baseline period and during procedures designed to elicit both positive and negative affect. There was a significant suppression of RSA during the negative affect task for nonexposed infants but not for exposed infants. Postnatal ETS exposure did not moderate this association; however, gender did moderate this association such that boys with prenatal cigarette exposure had a significant increase in RSA rather than the suppression seen among both nonexposed boys and girls. These results provide additional support for the idea that boys are particularly vulnerable to the effects of prenatal cigarette exposure.

Autonomic nervous system function following prenatal opiate exposure

In utero exposure to opiates may affect autonomic functioning of the fetus and newborn. We investigated heart rate variability (HRV) as a measure of autonomic stability in prenatal opiate-exposed neonates (n = 14) and in control term infants (n = 10). Electrocardiographic data during both non-nutritive and nutritive sucking were evaluated for RR intervals, heart rate (HR), standard deviation of the consecutive RR intervals (SDRR), standard deviation of the differences of consecutive RR intervals (SDDRR), and the power spectral densities in low and high frequency bands. In controls, mean HR increased significantly, 143-161 per min (p = 0.002), with a trend toward a decrease in RR intervals from non-nutritive to nutritive sucking; these measures did not change significantly among exposed infants. Compared to controls, exposed infants demonstrated significantly greater HRV or greater mean SDRR and SDDRR during non-nutritive period (p < 0.01), greater mean SDDRR during nutritive sucking (p = 0.02), and higher powers in the low and high frequency bands during nutritive feedings. Our findings suggest that prenatal opiate exposure may be associated with changes in autonomic nervous system (ANS) functioning involving both sympathetic and parasympathetic branches. Future studies are needed to examine the effects of prenatal opiate exposure on ANS function.

Profiles of Reactivity in Cocaine-Exposed Children

This study explored the possibility that specific, theoretically consistent profiles of reactivity could be identified in a sample of cocaine-exposed infants and whether these profiles were associated with a range of infant and/or maternal characteristics. Cluster analysis was used to identify distinct groups of infants based on physiological, behavioral and maternal reported measures of reactivity. Five replicable clusters were identified which corresponded to 1) Dysregulated/High Maternal Report Reactors, 2) Low Behavioral Reactors, 3) High Reactors, 4) Optimal Reactors and 5) Dysregulated/Low Maternal Report Reactors. These clusters were associated with differences in prenatal cocaine exposure status, birthweight, maternal depressive symptoms, and maternal negative affect during mother-infant interactions. These results support the presence of distinct reactivity profiles among high risk infants recruited on the basis of prenatal cocaine exposure and demographically similar control group infants not exposed to cocaine.

Physiological regulation in cigarette exposed infants: an examination of potential moderators

The primary purpose of this study was to examine pathways from prenatal cigarette exposure to physiological regulation at 2 months of age. Specifically, we explored the possibility that any association between prenatal cigarette exposure and infant physiological regulation was moderated by fetal growth, prenatal or postnatal environmental tobacco smoke (ETS) exposure or maternal depressive symptomatology during pregnancy. We evaluated whether exposed infants who were also exposed to ETS after birth, were small for gestational age (SGA) or had mothers with higher depressive symptoms during pregnancy had the highest levels of physiological dysregulation. Respiratory sinus arrhythmia (RSA) was obtained from 234 (166 exposed and 68 nonexposed) infants during sleep. As expected, cigarette-exposed infants had significantly lower RSA than nonexposed infants. This association was not moderated by prenatal or postnatal ETS exposure, or maternal depressive symptomatology during pregnancy. However, small for gestational age status did moderate this association such that nonexposed infants who were not small for gestational age had a significantly higher RSA than nonexposed small for gestational age infants and exposed infants. These findings provide additional evidence that prenatal cigarette exposure is directly associated with dysregulation during infancy.

A new look at quantifying tobacco exposure during pregnancy using fuzzy clustering

BACKGROUND

Prenatal tobacco exposure is a risk factor for the development of externalizing behaviors and is associated with several adverse health outcomes. Because pregnancy smoking is a complex behavior with both daily fluctuations and changes over the course of pregnancy, quantifying tobacco exposure is a significant challenge. To better measure the degree of tobacco exposure, costly biological specimens and repeated self-report measures of smoking typically are collected throughout pregnancy. With such designs, there are multiple, and substantially correlated, indices that can be integrated via new statistical methods to identify patterns of prenatal exposure.

METHOD

A multiple-imputation-based fuzzy clustering technique was designed to characterize topography of prenatal exposure. This method leveraged all repeatedly measured maternal smoking variables in our sample data, including (a) cigarette brand; (b) Fagerstrom nicotine dependence item scores; (c) self-reported smoking; and (d) cotinine level in maternal urine and infant meconium samples. Identified exposure groups then were confirmed using a suite of clustering validation indices based on multiple imputed datasets. The classifications were validated against irritable reactivity in the first month of life and birth weight of 361 neonates (Male(_n)=185; Female(_n)=176; Gestational Age_(Mean)=39weeks).

RESULTS

This proposed approach identified three exposure groups, non-exposed, lighter-tobacco-exposed, and heavier-tobacco-exposed based on high-dimensional attributes. Unlike cut-off score derived groups, these groupings reflect complex smoking behavior and individual variation of nicotine metabolism across pregnancy. The identified groups predicted differences in birth weight and in the pattern of change in neonatal irritable reactivity, as well as resulted in increased predictive power. Multiple-imputation-based fuzzy clustering appears to be a useful method to categorize patterns of exposure and their impact on outcomes.

Prenatal tobacco exposure: developmental outcomes in the neonatal period

Smoking during pregnancy is a persistent public health problem that has been linked to later adverse outcomes. The neonatal period--the first month of life--carries substantial developmental change in regulatory skills and is the period when tobacco metabolites are cleared physiologically. Studies to date mostly have used cross-sectional designs that limit characterizing potential impacts of prenatal tobacco exposure on the development of key self-regulatory processes and cannot disentangle short-term withdrawal effects from residual exposure-related impacts. In this study, pregnant participants (N = 304) were recruited prospectively during pregnancy, and smoking was measured at multiple time points, with both self-report and biochemical measures. Neonatal attention, irritable reactivity, and stress dysregulation were examined longitudinally at three time points during the first month of life, and physical growth indices were measured at birth. Tobacco-exposed infants showed significantly poorer attention skills after birth, and the magnitude of the difference between exposed and nonexposed groups attenuated across the neonatal period. In contrast, exposure-related differences in irritable reactivity largely were not evident across the 1st month of life, differing marginally at 4 weeks of age only. Third-trimester smoking was associated with pervasive, deleterious, dose–response impacts on physical growth measured at birth, whereas nearly all smoking indicators throughout pregnancy predicted level and growth rates of early attention. The observed neonatal pattern is consistent with the neurobiology of tobacco on the developing nervous system and fits with developmental vulnerabilities observed later in life.

Sex differences in heart rate variability during sleep following prenatal nicotine exposure in rat pups

The influence of both prenatal nicotine exposure (PNE; 6 mg/kg/day) and sex on heart rate (HR) regulation during sleep versus wakefulness was evaluated in 13, 16 and 26 day old rat pups. Pups were chronically instrumented at least 24 h before testing. On postnatal day 13 (P13), PNE males spent significantly more time in NREM sleep and demonstrated a greater drop in HR when transitioning from quiet wake to sleep compared to age and sex matched controls (-14±5 bpm versus -1±3 bpm, respectively). Heart rate variability (HRV) analysis indicated that this state-dependent drop in HR was primarily associated with a greater reduction in sympathovagal balance (LF/HF ratio) in PNE males compared to controls. No parallel changes in indices of parasympathetic drive (HF power) were identified. In contrast, no significant effect of PNE on HR during sleep versus wakefulness was identified in P13 females. However, independent of state, a significant decrease in HF power was identified in P13 PNE females compared to controls. At P16, state-dependent differences in HR or HRV between PNE and sex-matched control pups were resolved. Additionally, at P26 no significant effect of PNE on state-dependent changes in HR or HRV was identified in either sex. Analysis of the hypothalamic peptide orexin identified that PNE induced approximately a 50% reduction in hypothalamic prepro-orexin mRNA and total mRNA was lowest in PNE males. These findings suggest that PNE induces sex dependent changes in sleep related autonomic regulation of HR during early postnatal development and these changes may be related to epigenetic alterations in the orexin system.

Using propensity score modeling to minimize the influence of confounding risks related to prenatal tobacco exposure

INTRODUCTION

Despite efforts to control for confounding variables using stringent sampling plans, selection bias typically exists in observational studies, resulting in unbalanced comparison groups. Ignoring selection bias can result in unreliable or misleading estimates of the causal effect.

METHODS

Generalized boosted models were used to estimate propensity scores from 42 confounding variables for a sample of 361 neonates. Using emergent neonatal attention and orientation skills as an example developmental outcome, we examined the impact of tobacco exposure with and without accounting for selection bias. Weight at birth, an outcome related to tobacco exposure, also was used to examine the functionality of the propensity score approach.

RESULTS

Without inclusion of propensity scores, tobacco-exposed neonates did not differ from their nonexposed peers in attention skills over the first month or in weight at birth. When the propensity score was included as a covariate, exposed infants had marginally lower attention and a slower linear change rate at 4 weeks, with greater quadratic deceleration over the first month. Similarly, exposure-related differences in birth weight emerged when propensity scores were included as a covariate.

CONCLUSIONS

The propensity score method captured the selection bias intrinsic to this observational study of prenatal tobacco exposure. Selection bias obscured the deleterious impact of tobacco exposure on the development of neonatal attention. The illustrated analytic strategy offers an example to better characterize the impact of prenatal tobacco exposure on important developmental outcomes by directly modeling and statistically accounting for the selection bias from the sampling process.

Neonatology and the Environment: Impact of Early Exposure to Airborne Environmental Toxicants on Infant and Child Neurodevelopment

Environmental contaminants pose a threat to infant neurodevelopment. In this current paper, we discuss evidence for the potentially harmful impact of fetal and early childhood exposure to polycyclic aromatic hydrocarbons (PAHs), environmental tobacco smoke (ETS), and organophosphorus (OP) insecticides. We focus on effects resulting from chronic and low-level exposure during the prenatal period and early childhood, when the brain is still undergoing rapid developmental changes.

The association between prenatal cocaine exposure and physiological regulation at 13 months of age

BACKGROUND

This study examined the association between prenatal cocaine exposure (PCE) and autonomic regulation at 13 months of age.

METHODS

Measures of respiratory sinus arrhythmia (RSA) were obtained from 156 (79 exposed, and 77 nonexposed) infants during baseline and during tasks designed to elicit positive (PA) and negative affect (NA).

RESULTS

There was a significant suppression of RSA during the negative affect task for nonexposed infants but not for exposed infants. Maternal symptoms of depression or anxiety (MDA) did not mediate this association. However, gender and MDA did moderate this association such that exposed boys and exposed infants whose mothers had higher levels of MDA had an increase in RSA during a task designed to elicit NA rather than the typical pattern of RSA suppression.

CONCLUSIONS

These results suggest that there are several possible pathways from PCE to physiological dysregulation during late infancy.

Application of Psychobiological Measures in Occupational Science and Occupational Therapy Research

The authors discuss the use of psychobiological measures (i.e., biomarkers) for furthering understanding of the biological foundations supporting human occupational behavior. They explore the possible applications of psychobiological measures in research relevant to occupational therapy practice and occupational science, including the documentation of outcomes following occupational therapy intervention. Common psychobiological measures that are available and of particular interest to occupational scientists and therapists are described based on a review of research that has applied psychobiological measures. Psychobiological measures have rarely been reported in the occupational science and occupational therapy literature to date, although such measures are beginning to emerge as researchers expand their questions and methods related to occupational engagement. Psychobiological measures may provide promising insights into the effectiveness of interventions designed to improve self-regulation and more effectively manage stressors for enhancing occupational performance. These measures also may be used to increase understanding of how participation in desired occupations influences arousal levels, stress response, and overall states of well-being and productivity.

The impact of maternal smoking on fast auditory brainstem responses

Deficits in auditory processing have been posited as one of the underlying neurodevelopmental consequences of maternal smoking during pregnancy that leads to later language and reading deficits. Fast auditory brainstem responses were used to assess differences in the sensory processing of auditory stimuli among infants with varying degrees of prenatal cigarette exposure. Maternal report of consumption of cigarettes and blood samples were collected in the hospital to assess exposure levels and participants were then seen at 6-months. To participate in the study, all infants had to pass the newborn hearing exam or a clinically administered ABR and have no known health problems. After controlling for participant age, maternal smoking during pregnancy was negatively related to latency of auditory brainstem responses. Of several potential covariates, only perinatal complications and maternal alcohol use were also related to latency of the ABR responses and maternal smoking level accounted for significant unique variance after controlling for these factors. These results suggest that the relationship between maternal smoking may lead to disruption in the sensory encoding of auditory stimuli.

Prenatal Cocaine Exposure and Infant Sleep at 7 Months of age: The Influence of the Caregiving Environment

The primary goal of this study was to examine sleep problems in a sample of cocaine-exposed 7-month-old infants and to determine if maternal psychopathology mediated any existing association between substance exposure and sleep behaviors. We also examined the differences in sleep behaviors of cocaine-exposed infants in parental custody and cocaine-exposed infants in nonparental custody. Participants were 65 cocaine-exposed and 53 nonexposed infants and their primary caregivers who were recruited at delivery and assessed at 7 months of infant age. As expected, women who used cocaine during pregnancy had more psychiatric symptoms than nonusers. Prenatal exposure to heavier amounts of cocaine was significantly related to more severe sleep difficulties, and maternal anxiety mediated this association. Approximately 28% of cocaine mothers lost custody of their infants by 7 months of age. Nonmaternal caregivers had significantly fewer symptoms of psychopathology than the cocaine-using women who retained custody of their children. Infants who were in nonparental care at 7 months of age also had less severe sleep problems than did infants who remained in parental care.