To examine the relationship between maternal intimate partner violence (IPV) and asthma onset in children and the role of supportive caregiving factors in modifying this relationship.
Prospective birth cohort.
In-person interview at enrollment as well as in-home interviews during study follow-up.
Children (N = 3116) enrolled in the Fragile Families and Child Wellbeing Study.
Maternal report of IPV assessed after the child's birth and at 12 and 36 months. In addition, mothers indicated how many days a week they participated in activities with the child and the amount and type of educational/recreational toys available for the child.
Main Outcome Measure
Maternal report of physician-diagnosed asthma by age 36 months.
Asthma was diagnosed in 19% of children. In adjusted analysis, children of mothers experiencing IPV chronically, compared with those not exposed, had a 2-fold increased risk of developing asthma. In stratified analysis, children of mothers experiencing IPV and low levels of mother-child activities (relative risk, 2.7; 95% confidence interval, 1.6-4.7) had a significant increased risk for asthma. Those exposed to IPV and high levels of mother-child activities had a lower risk for asthma (relative risk, 1.6; 95% confidence interval, 0.9-3.2). A similar buffering effect was noted among children with high numbers of educational/recreational toys.
Intimate partner violence is associated with increased early childhood asthma risk. Maternal ability to maintain positive caregiving processes in this context may buffer the effects of violence on child asthma risk. The best way to promote positive health in toddlers may be to help their mothers.
Evidence linking psychological stress to asthma continues to grow with our increased understanding of the natural history of asthma and the neurobiology underlying stress vulnerability.1- 3 Stress exposure during infancy and early childhood may exert particularly robust effects on the physiological systems that respond to stress.4- 6 Evidence from animal and human studies strongly suggests that early life adversity shapes stress neurobiology,7 resulting in disturbed regulation of endocrine and autonomic processes (eg, hypothalamic-pituitary-adrenal [HPA] axis, sympathetic-adrenal-medullary system). These disturbed patterns of stress regulation are hypothesized to subsequently modulate immune function, increasing susceptibility to asthma and related diseases.8
Developmental psychologists purport that the ability to regulate one's responses to stress (“self-regulation”) emerges in the context of the caregiver-child relationship, particularly in the first 3 years of life. Self-regulation involves the ability to modify the intensity and duration of physiological arousal, attention, and affective states to protect oneself from becoming overwhelmed by stimulation and modulate one's emotional expressions and social behaviors9,10 and is an important predictor of resilience among children.11- 13 That is, in the face of stress, children with good self-regulation skills have better adaptive behavior and coping strategies.12 In the infancy and toddler periods, sensitive and emotionally engaged caregiving has been found to buffer the reactivity of the child's stress regulation systems and promote state and arousal regulation at the physiological, affective, and behavioral levels, with self-regulation emerging as a major developmental milestone of the preschool period.14,15 It has been proposed that insensitive maternal-child interactions in early life may result in disturbed stress reactivity and impaired self-regulation abilities and, consequently, disrupted neuroimmune development, setting the stage for asthma.7 Notably, increased levels of negative affect and emotion dysregulation have been documented among children with severe asthma.16 Also, among children with asthma, difficulties with emotion regulation have been found to increase asthma severity,6 supporting a link between regulation and asthma.
Considering the caregiver's critical role in shaping the child's stress regulation systems in early development, factors that increase maternal stress and influence parenting behaviors may be particularly relevant in the etiology of asthma.17,18 Maternal exposure to intimate partner violence (IPV) has been identified as such a stressor. Cross-sectional evidence suggests that maternal IPV is associated with decreased lung function19 and increased child asthma risk in early development20 as well as children's behavioral and physiological stress reactivity and emotional and behavioral development.21- 23 However, while mothers experiencing IPV show increased levels of stress, they do not always show deficient parenting. Van Horn and Lieberman24 suggest that women experiencing IPV are remarkably similar to comparison women in their beliefs about parenting, self-reported parenting behaviors, and observed interactions with their children. Other evidence shows that while some mothers in violent relationships were struggling with parenting, other mothers seemed to compensate for the violence by becoming more effective parents.25 Therefore, the effects of maternal IPV on child health outcomes may be attenuated if mothers are able to maintain supportive caregiving in this context.
The goal of the current study was to prospectively examine associations between maternal IPV and child asthma risk and to consider the potentially buffering effects of the maintenance of supportive caregiving on this relationship. The supportive caregiving factors included in the current analyses—positive maternal-child activities and cognitive stimulation—have been associated with the development of optimal child self-regulation abilities.26- 29
Analyses were conducted using public-use data available from the Fragile Families and Child Wellbeing Study, a prospective birth cohort study that follows up a nationally representative sample of children from 20 large cities in the United States. Nonmarital births were oversampled relative to marital births in a ratio of 3 to 1. The study is a joint effort by the Princeton University Center for Research on Child Wellbeing and Center for Health and Wellbeing, the Columbia Population Research Center, and the National Center for Children and Families at Columbia University (http://www.fragilefamilies.princeton.edu). Details on the study design can be found in Reichman et al.30 In brief, 4789 women were recruited from 75 hospitals during childbirth in 20 US cities with populations more than 200 000. Random samples of both married and unmarried births were selected until preset quotas were reached based on the percentage of nonmarital births in the city that occurred at that hospital in 1996 or 1997. Families were excluded if any of the following criteria were met: mother planned to place the child for adoption; father of the baby was not living at the time of the birth; mother did not speak either English or Spanish well enough to complete the interview; mother or baby was too ill for the mother to complete the interview; or baby died before the interview could take place. Among eligible mothers, 82% of those married and 87% of those unmarried agreed to participate. Mothers completed a baseline interview at delivery and participated in follow-up interviews when the children were approximately 12 and 36 months of age. At the time of the 36-month in-home assessment, 3288 families remained in the study.30 No significant differences were found between those who did and did not complete the 36-month follow-up assessment on baseline demographics or IPV exposure. In addition, 172 children were missing data on other covariates, leaving 3116 children for the current analyses.
Maternal IPV was assessed at baseline and at the 12- and 36-month assessments, with study questions, previously validated,31,32 varying slightly between baseline and follow-up assessments. At baseline, mothers were asked to think about their relationship with the baby's father and asked how often does “he hit or slap you when he is angry?” Mothers who responded “often” or “sometimes” as opposed to “never” were categorized as experiencing baseline IPV. At 12 and 36 months, mothers were asked to think about their relationship with the baby's father or current partner and were then asked: “How often does he slap or kick you?” “How often does he hit you with a fist or object that could hurt you?” and “Were you ever cut or bruised or seriously hurt in a fight with the baby's father or current partner?” Mothers who responded “often” or “sometimes” as opposed to “never” to either of the first 2 questions or who responded yes to the third question were categorized as experiencing IPV for the relevant follow-up period. Physical IPV was characterized as (1) never experiencing IPV, (2) occurring prior to 12 months only (endorsed at baseline and/or 12-month follow-up), (3) occurring between 12 and 36 months only (endorsed at 36 months only), or (4) occurring both prior to 12 months and also between 12 and 36 months (chronic exposure).
During the 36-month follow-up interview, mothers were asked whether a physician had diagnosed the child with asthma, a standard approach with demonstrated reliability and validity. Parent-reported physician-diagnosed asthma is associated with more objective outcomes (eg, airway hyperresponsiveness) and more severe disease.33 Moreover, this definition is used by the National Center for Health Statistics in surveys of the US population to facilitate generalizability.34
Based on prior work on caregiving characteristics important in the development of self-regulatory processes,27- 29,35,36 factors reflective of supportive caregiving were categorized across 2 domains: engagement in mother-child activities and availability of educational/recreational toys as a measure of cognitive stimulation. Both factors were assessed at the 36-month assessment.
Mothers reported how many days a week they gave the child physical affection (eg, told the child she loved him or her, gave the child hugs or physical affection), spent time with the child in various activities (eg, read or told stories, played with toys or imaginary games, and sang songs), and assisted the child with eating and bedtime. Exploratory factor analysis with orthogonal rotation was used to uncover the number of latent constructs underlying this set of 10 items. A cutoff of 0.40 was used for factor loading with an eigenvalue greater than 1, which allows the extracted factor to explain a reasonable proportion of the total variance. Principal components analysis of the 10 items revealed 3 factors that explained 52% of the total variance: 1 factor included the 2 items on physical affection, a second factor included the 6 items on mother-child activities, and a third factor included the 2 items on eating and bedtime. Closer examination revealed that 98% of the mothers reported expressing physical affection toward their child every day and 97% reported telling the child she loved him or her every day. Because of the limited variability of these 2 items, a scale of mother-child activities was created summing the 6 items that loaded onto the second factor, corresponding to activities such as reading, singing songs, telling stories, playing with toys, or playing imaginary games. Scale scores ranged from 0 to 42, with higher scores indicating a higher number of different activities and a higher frequency of activities. Scale reliability was found to be adequate (Cronbach α = .74).
Mothers quantified the number of educational materials and recreational toys available in the home, including books, toys that make music, toys that have pieces that fit together, push or pull toys, toys that let the child work his or her muscles, toys that can be put together in different ways, cuddly toys, and toys with wheels. Mothers were asked whether their children owned none, 1 to 2, 3 to 4, or 5 or more of each of these types of toys/books. Principal component factor analyses revealed 2 factors that explained 50% of the total variance: 1 factor for the 6 toy items and another factor with 2 items (books and cuddly toys). Because 90% of mothers reported their children owned 5 or more books, a scale consisting of educational/recreational toys was created by summing the 6 items on toys. Scale scores ranged from 0 to 18, with higher scores indicating a higher number of toys as well as a greater diversity of toys. Scale reliability was found to be adequate (Cronbach α = .75).
The baseline and follow-up questionnaires ascertained information on sociodemographic factors, including maternal race/ethnicity, maternal education level, and child sex, as well as maternal smoking and birth weight of the child. Racial/ethnic minorities as well as those of lower socioeconomic status (SES) experience higher rates of family violence as well as higher rates of asthma37 than their white, higher-SES counterparts.38- 40 Analyses were therefore adjusted for maternal race/ethnicity and maternal education level. We further adjusted for SES based on maternal report on whether they had faced any of the following economic hardships in the past year (yes/no): not having enough money to pay full electricity, gas, or oil bill; having to borrow money from friends or family; moving in with other people because of financial problems; staying in a shelter, car, or abandoned building; being evicted from their home; not having enough money to pay rent or mortgage; and receiving free food or meals. Economic hardship in the past year was categorized as responding yes to 1 or more of these questions. Women who experience IPV are also more likely to have lower-birth-weight babies,41 a risk factor that has also been linked with increased childhood asthma risk.42,43 Birth weight was categorized as less than 2.5 kg compared with 2.5 kg and higher. Furthermore, because smoking (maternal and other sources) has been shown to be associated with more stressful violent environments44- 46 and with asthma prevalence,47 tobacco exposure was included as another potential confounder. Mothers reported whether they smoked during pregnancy at the baseline assessment. During follow-up assessments, mothers were asked to report on their current smoking status and whether anyone in the household smoked. Child tobacco smoke exposure was categorized as follows: (1) no exposure; (2) postnatal tobacco smoke exposure only; and (3) both in utero and postnatal tobacco smoke exposure. There were few children with in utero tobacco exposure but no postnatal exposure (3.5%, n = 110); hence, they were included in the in utero and postnatal tobacco smoke exposure category.
Summary measures of continuous covariates are reported as mean and standard deviation unless otherwise noted. Logistic regression analyses were conducted to estimate the effect of maternal IPV on asthma diagnosed by age 36 months while adjusting for potential confounders (child's sex, age, race/ethnicity, low birth weight, maternal education, economic hardship, and tobacco exposure). First, a model was run regressing maternal IPV occurring during at least once (ever) on child's asthma diagnosis. Next, a regression model was run accounting for chronicity of exposure to maternal IPV (exposure in both postnatal periods). Lastly, 2 separate logistic regression models were run regressing maternal IPV on child's asthma diagnosis, stratified by the supportive caregiving factors: mother-child activities (model 1) stratified by the median score of the scale and educational/recreational toys (model 2) stratified by the median score of the scale. All analyses were conducted in SAS version 9.0 (SAS Institute, Cary, North Carolina).
Among the 3116 children available for analyses, 52% were boys, 48% were black, 26% were Hispanic, 19% had been diagnosed with asthma, and 16% lived in a household with maternal IPV at some time during follow-up (Table 1). The mean (SD) score on the mother-child activities scale was 31 (8.6), and the mean (SD) score on the educational/recreational toys scale was 12 (3.8). The mother-child activities scale and the educational/recreational toy scale scores were moderately correlated (r = 0.25; P < .001). Neither scale was significantly correlated with SES (P > .05).
In adjusted analysis, children of mothers experiencing IPV at any point, compared with those not exposed, were at increased risk of developing asthma (relative risk [RR], 1.3; 95% confidence interval [CI], 1.0-1.7]. Children of mothers experiencing IPV in only one period, that is, prior to 12 months or at 36 months only, did not have a significant increased risk for asthma compared with children never exposed (Table 2). Those exposed to IPV during both points (chronic exposure) had a 2-fold risk (RR, 2.1; 95% CI, 1.4-3.2) of having an asthma diagnosis.
In stratified analyses, children of mothers experiencing IPV chronically and who had a lower level of mother-child interactions were at increased risk of developing asthma (RR, 2.7; 95% CI, 1.6-4.7) compared with thosenot exposed to IPV with low mother-child interactions (Figure 1). No significant associations were noted among children of mothers experiencing IPV chronically with high mother-child interactions (RR, 1.6; 95% CI, 0.9-3.2) compared with those not exposed with high mother-child interactions. Similarly, children of mothers experiencing IPV chronically and with low levels of educational/recreational toys were at increased risk of developing asthma (RR, 2.5; 95% CI, 1.5-4.1) compared with those not exposed with low levels of educational/recreational toys (Figure 2). Children of mothers experiencing IPV chronically with higher levels of educational/recreational toys did not have an increased risk of developing asthma (RR, 1.6; 95% CI, 0.8-3.4) compared with those not exposed with high levels of educational/recreational toys.
Risk of child asthma by maternal intimate partner violence stratified by mother-child activities. Models were adjusted for child's age, sex, race/ethnicity, maternal education, economic hardship, tobacco exposure, and low birth weight. Error bars show 95% confidence interval.
Risk of child asthma by maternal intimate partner violence stratified by availability of educational/recreational toys. Models adjusted for child's age, sex, race/ethnicity, maternal education, economic hardship, tobacco exposure, and low birth weight. Error bars show 95% confidence interval.
These prospective data demonstrate that maternal IPV is associated with increased early childhood asthma risk. Cumulative or chronic exposure to violence was most clearly associated with asthma risk, consistent with the notion that stress beginning in infancy may sensitize children to later stress and more adverse consequences. This is consistent with the findings of Essex and colleagues,48 who examined associations among maternal stress and preschoolers' physiological stress response and later mental health. Analyses showed that children exposed to stress only in infancy or only in the preschool period had cortisol levels similar to those never exposed to stress, whereas children exposed to maternal stress in infancy and preschool had elevated cortisol levels. These findings are also in line with other studies that have shown that chronic caregiver stress in the postpartum and early childhood period has been associated with persistent wheeze in early childhood4 as well as factors that may initiate or potentiate inflammation in the lung (eg, IgE expression, enhanced nonspecific and allergen-specific lymphocyte proliferation, differential cytokine expression).5,7 Both persistent wheeze and atopy have been linked to reduced lung function in childhood.49 This cumulative stress model is particularly relevant given that maternal IPV may become a more direct stressor for toddlers who are witnessing violence against their mothers.50
Our analyses further show that, while maternal IPV is associated with increased childhood asthma risk, factors contributing to a supportive caregiving environment appear to buffer the maternal IPV–asthma association. While no other studies, to our knowledge, have explored the buffering effects of the caregiving environment in the stress-asthma association, animal studies have shown that environmental enrichment can reverse the effects of early stress experiences on stress reactivity.51 Laviola et al52 and Morley-Fletcher et al53 have shown that environmental enrichment eliminates the outcomes of prenatal stress on corticosterone response and reactivity to an immune-suppressive agent. Similarly, Francis et al54 have shown that environmental enrichment can reverse the effects of early stress on HPA activation and behavioral response to stress. In humans, parental social support has been shown to be inversely associated with asthma prevalence among children.55 Furthermore, maternal sensitivity has been shown to modify the effects of prenatal stress experiences on infant stress reactivity.56
The stress-health paradigm provides a useful framework to link maternal IPV to child health effects. Numerous studies suggest that maternal stress experienced in utero influences programming of key physiological systems that contribute to childhood disease57 and that nonoptimal early childhood environments and caregiving experiences also influence these processes.58- 61 Specifically, emerging data implicate the disruptive impact of stress on the HPA, autonomic, neuroendocrine, and immune systems.1,3,7,57,62 Disruptions of these stress regulatory systems may, in turn, be linked to immune dysregulation, increasing vulnerability to the development of diseases such as asthma.
In humans, both the HPA system and the autonomic nervous system show developmental changes in infancy, with the HPA axis becoming organized between 2 and 6 months of age and the autonomic nervous system demonstrating relative stability by 6 to 12 months of age.63 The HPA axis in particular has been shown to be highly responsive to child-caregiver interactions, with sensitive caregiving programming the HPA axis to become an effective physiological regulator of stress and insensitive caregiving promoting hyperreactive or hyporeactive HPA systems.17 Several animal models as well as human studies also support the connection between caregiver experiences in early postnatal life and alterations of autonomic nervous system balance.63- 65 Furthermore, children who have a history of sensitive caregiving are more likely to demonstrate optimal affective and behavioral strategies for coping with stress.66,67 Therefore, children with histories of supportive, sensitive caregiving in early development may be better able to self-regulate their physiological, affective, and behavioral responses to environmental stressors and, consequently, less likely to manifest disturbed HPA and autonomic reactivity that put them at risk for stress-related illnesses such as asthma.
While these data allow us to explore prospective relationships between maternal IPV and childhood asthma, there are limitations worth mentioning. As is typical with longitudinal studies, there was a reduction in the sample available from the original cohort over time. However, there were no differences based on race/ethnicity, maternal education, smoking status, low birth weight, or maternal IPV at baseline between those who completed the 36-month assessment and those who did not. While we were able to adjust for a number of factors associated with asthma and violence exposure, the associations found in this study may be attributable to unmeasured or residual confounding. For example, we were unable to adjust for traffic exposures or other environmental exposures that have been shown to affect asthma and to be more common in lower-SES, higher–social risk households.68 It is possible that mothers may have underreported IPV or overreported positive caregiving factors to present more socially desirable responses. However, this potential misclassification of exposure is likely nondifferential with respect to the outcome and thus unlikely to account for the observed associations. A lack of a buffering effect of caregiving factors among children exposed to IPV before the 36-month follow-up could be due to the timing of the assessment of caregiving factors, which occurred at the 36-month assessment. Quality of parental caregiving has been shown to be relatively stable over time, with changes in caregiving quality predicted by changes in maternal life circumstances (eg, changes in overall life support, increase in life stress, and change in partner status).67 It is likely then that in a population where IPV is not stable over time, parental caregiving practices are also changing.
This study demonstrates a relationship between chronic maternal IPV and development of childhood asthma. Furthermore, our results suggest that supportive caregiving may buffer the effects of violence. Among children chronically exposed to IPV, a lower risk of asthma was found among children with higher levels of positive mother-child interactions and cognitive stimulation. While public health intervention should be aimed at eliminating maternal IPV, understanding factors that can buffer the effects of domestic violence in children may inform prevention strategies that can potentially benefit not only their psychological well-being, but also their physical health. The best way to promote positive health in infants and toddlers may be to support their mothers and intervene around factors influencing parenting behaviors, including IPV.
Correspondence: Shakira Franco Suglia, MS, ScD, Department of Environmental Health, Harvard School of Public Health, Landmark 415W, 401 Park Dr, Boston, MA 02215 (firstname.lastname@example.org).
Accepted for Publication: August 29, 2008.
Author Contributions:Study concept and design: Franco Suglia, Bosquet Enlow, Kullowatz, and Wright. Acquisition of data: Franco Suglia and Wright. Analysis and interpretation of data: Franco Suglia, Bosquet Enlow, and Wright. Drafting of the manuscript: Franco Suglia and Wright. Critical revision of the manuscript for important intellectual content: Franco Suglia, Bosquet Enlow, and Kullowatz. Statistical analysis: Franco Suglia. Obtained funding: Franco Suglia and Wright. Administrative, technical, and material support: Kullowatz and Wright.
Financial Disclosure: None reported.
Funding/Support: Support was provided by the Robert Wood Johnson Foundation New Connections Initiative Award (Dr Franco Suglia) and National Institutes of Health grants T32MH073122-04 (Dr Franco Suglia), R01HL080674 (Dr Wright), and K08MH074588 (Dr Bosquet Enlow).
Suglia SF, Enlow MB, Kullowatz A, Wright RJ. Maternal Intimate Partner Violence and Increased Asthma Incidence in ChildrenBuffering Effects of Supportive Caregiving. Arch Pediatr Adolesc Med. 2009;163(3):244-250. doi:10.1001/archpediatrics.2008.555