Respiratory symptoms in the first 7 years of life and birth weight at term: the PIAMA Birth Cohort

Association of exposure to fine particulate matter wave over the preconception and pregnancy periods with adverse birth outcomes: Results from the project ELEFANT

BACKGROUND

No study has explored the effects of sustained maternal exposure to high-level ambient fine particulate matter (PM_2.5) within a short period, i.e., PM_2.5 wave, on adverse birth outcomes, though increasing epidemiological studies demonstrated that exposure to single days of high ambient PM_2.5 could increase risks of adverse birth outcomes. In this study, we aim to evaluate associations of maternal PM_2.5 wave exposure around pregnancy with preterm birth (PTB), small for gestational age (SGA), and large for gestational age (LGA).

METHODS

Totally 10,916 singleton pregnant women from all 16 districts in Tianjin, China, and their followed-up birth outcomes were included in this study. We defined PM_2.5 wave as at least 2 consecutive days with daily average PM_2.5 concentration exceeding 75 μg/m³, and 90th, 92.5th, 95th, 97.5th, 99th percentiles of PM_2.5 distribution during the study period in Tianjin, respectively. Cox proportional hazard model was applied to evaluate the durational effects of PM_2.5 wave during each exposure window on PTB, SGA, and LGA after adjusting for potential confounders.

RESULTS

Exposure to PM_2.5 wave over the preconception and pregnancy periods was associated with increased risks of adverse birth outcomes. For PTB, the strongest association was found during the first trimester when PM_2.5 wave was defined as at least 4 consecutive days with daily average PM_2.5 concentration >90th (HR, 10.46; 95% CI, 6.23-17.54); and for SGA (HR, 6.23; 95% CI, 3.34-11.64) and LGA (HR, 4.70; 95% CI, 3.35-6.59), the strongest associations both were found when PM_2.5 wave was defined as at least 2 consecutive days with daily average PM_2.5 concentration >99th. Additionally, the risks of adverse birth outcomes generally increased at higher PM_2.5 thresholds or longer durations of PM_2.5 wave.

CONCLUSION

Prolonged exposure to high-level PM_2.5 over preconception and pregnancy periods was associated with increasing risks of PTB, SGA and LGA.

Individual and contextual socioeconomic status as effect modifier in the air pollution-birth outcome association

BACKGROUND

Several studies have examined whether air pollution is associated with adverse births outcomes, but it is not clear if socioeconomic status (SES) modifies this relationship.

OBJECTIVES

We investigated if maternal education and area-level socioeconomic status modified the relationship between ozone, nitrogen dioxide and particulate matter with aerodynamic diameter <10 μm (PM₁₀) on preterm births (PTB; gestational age <37 weeks) and term low birth weight (TLBW; weight < 2500 g on term deliveries).

METHODS

Analyses were based on almost 1 million singleton live births in São Paulo municipality between 2011 and 2016. The final sample included 979,306 births for PTB analysis and 888,133 for TLBW analysis. Exposure to PM₁₀, NO₂ and O₃ were based on date of birth and estimated for the entire gestation and for each trimester. Multilevel logistic regression models were conducted to examine the effect of air pollutants on both adverse birth outcomes and whether it was modified by individual and area-level SES.

RESULTS

In fully adjusted models, over the entire pregnancy, a 10 μg/m³ increase in O₃ and PM₁₀ was associated with increased chance of PTB (odds ratio; OR = 1.14 CI 1.13, 1.16 and 1.08 CI = 1.02, 1.15 respectively) and PM₁₀ with TLBW (OR = 1.08 CI 1.03, 1.14). Associations were modified by maternal educational and area-level SES for both outcomes. Mothers of lower education had an additional chance of PTB and TLBW due to PM₁₀ exposure (OR = 1.04 CI 1.04, 1.05 and 1.10 CI 1.08, 1.14 respectively), while mothers living in low SES areas have an additional chance for TLBW (OR = 1.05 CI 1.03, 1.06). Similar modification effects were found for O₃ exposure. Trimester specific associations were weaker but followed a similar pattern.

CONCLUSION

Socioeconomic status modifies the effect of air pollution on adverse birth outcomes. Results indicate that mothers with lower SES may be more susceptible to air pollution effects.

Accelerated decline in lung function in adults with a history of remitted childhood asthma

AIM

A significant number of children with asthma show remission in adulthood. Although these adults are often diagnosed with chronic obstructive pulmonary disease in later life, the effect of clinically remitted childhood asthma on the decline in lung function during adulthood is uncertain. We examined whether clinical remission of childhood asthma was associated with an accelerated decline in lung function in apparently non-asthmatic adults.

METHODS

Here, 3584 participants (mean age, 48.1 years; range, 35-65 years) who did not have adulthood asthma and other lung diseases and had normal lung function at the baseline visit were included. They were categorised as follows: those with remitted childhood asthma (n=121) and healthy controls (n=3463) according to their self-reported childhood asthma history. Spirometry was performed at baseline and follow-up visits.

RESULTS

The mean follow-up time was 5.3 years. Multivariate regression analysis showed that remitted childhood asthma and smoking were independently associated with a rapid decline in forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC). Besides, smoking was an independent predictor of a rapid decline in the FEV₁/FVC. The annual decline in FEV₁ and FVC was significantly greater in participants with remitted childhood asthma than in healthy controls, and the differences remained significant after adjusting for the propensity score.

CONCLUSION

A history of clinically remitted childhood asthma is an independent risk factor for accelerated decline in lung function in adults. Remitted childhood asthma and smoking may additively accelerate the development of obstructive lung disease.

Are prenatal anxiety or depression symptoms associated with asthma or atopic diseases throughout the offspring's childhood? An updated systematic review and meta-analysis

Background

Asthma is the most common respiratory disease among children, while atopic diseases such as atopic dermatitis affect about 20% of infants under 2 years of age. Studies suggested that these conditions might be related to prenatal depression or anxiety. This study aimed to explore the association between prenatal mental disorders and childhood asthma or atopic disease in a systematic review and meta-analysis.

Methods

PubMed, Embase, and the Cochrane Library were searched up to May 2020. The primary outcome was childhood asthma and childhood atopic dermatitis. Random-effects models were used because of high heterogeneity indicated by I² > 50% and Q-test P < 0.10.

Results

A total of 598 studies were initially identified, but nine studies met the inclusion criteria. Prenatal mental disorder was associated with childhood asthma (n = 6 studies; ES = 1.146, 95%CI: 1.054–1.245, P = 0.001; I² = 93.5%, P_{heterogeneity} < 0.001) whereas no significant association was found for childhood atopic dermatitis (n = 4 studies; ES = 1.211, 95%CI: 0.982–1.494, P = 0.073; I² = 78.5%, P_{heterogeneity} < 0.001). Childhood asthma seems to be related more to depression (n = 1 study; ES = 1.170, 95%CI: 1.061–1.291, P = 0.002) and anxiety/depression (n = 4 studies; ES = 1.157, 95%CI: 1.050–1.275, P = 0.073; I² = 95.3%, P_{heterogeneity} < 0.001).

Conclusion

This meta-analysis demonstrated that prenatal mental disorders increase the risk of childhood asthma. We limited the included samples to pregnant women to investigate the association between prenatal psychological factors and offspring’s physical health. Future studies should include large high-quality cohort studies to investigate the behavioral, environmental, and genetic causes for this association.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-03909-z.

Associations of adverse pregnancy outcomes with high ambient air pollution exposure: Results from the Project ELEFANT

BACKGROUND

Investigations on the potential effects of high air pollution exposure before pregnancy on adverse pregnancy outcomes are limited, and it is unknown whether air quality standards looser than that set by World Health Organization (WHO) still can provide sufficient protection pregnant women from adverse pregnancy outcomes.

OBJECTIVES

To evaluate the potential effects of high ambient air pollution around pregnancy on preterm birth (PTB) and low birth weight (LBW), and assess the risk of PTB and LBW associated with air pollutants with reference to different air quality standards of WHO and China.

METHODS

Our study leveraged 10,960 pregnant women from the Project ELEFANT. Daily average particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO) and ozone (O₃) concentrations were collected based on Chinese Air Quality Reanalysis datasets. Hazard ratios (HR) of PTB and LBW were estimated for maternal PM_2.5, PM₁₀, NO₂, SO₂, CO and O₃ exposures and related proportions of days with daily average air pollution concentrations exceeding air quality standards of WHO and China around pregnancy using Cox proportional hazards regression models with adjustment for potential confounders.

RESULTS

Ambient PM_2.5, PM₁₀, NO₂, SO₂ and CO exposure during the before pregnancy and pregnancy period were both significantly and positively associated with increased risk of PTB, PTB subtypes and LBW. A 10% increase in proportion of days with daily average PM_2.5 exceeding 25 μg/m³ over the entire pregnancy was most apparently associated with risk of PTB (HR, 12.66; 95% CI, 8.20-19.53) and LBW (HR, 17.42; 95% CI, 6.88-44.10) among all PM_2.5 proportion variables based on different air quality standards.

CONCLUSION

Air quality standards of WHO are necessary to be implemented to control for risks of adverse pregnancy outcomes associated with ambient air pollution in areas with high air pollution levels.

Impact of air pollution on low birth weight in Spain: An approach to a National Level Study

BACKGROUND

According to the WHO, low birth weight (<2500 gr) is a primary maternal health indicator as the cause of multiple morbi-mortality in the short and long-term. It is known that air pollution from road traffic (PM₁₀, NO₂) and O₃ have an important impact on low birth weight (LBW), but there are few studies of this topic in Spain. The objective of this study is to determine the possible exposure windows in the gestational period in which there is greater susceptibility to urban air pollution and to quantify the relative risks (RR) and population attributable risks (PAR) of low birth weight associated with pollutant concentrations in Spain.

METHODS

We calculated the weekly average births with low birth weight (ICD-10: P07.0-P07.1) for each Spanish province for the period 2001-2009, using the average weekly concentrations of PM₁₀, NO₂ and O₃, measured in the capital cities of the provinces. The estimation of RR and PAR were carried out using generalized linear models with link Poisson, controlling for the trend, seasonality and auto-regressive character of the series and for the influence of temperature during periods of heat waves and/or cold. Finally, a meta-analysis was used to estimate the global RR and PAR based on the RR obtained for each of the provinces.

RESULTS

The RR for the whole of Spain is 1.104 (CI95%: 1.072, 1.138) for the association between LBW and PM₁₀, and 1.091 (CI95%: 1.059, 1.124) for the association between NO₂ and LBW. Our results suggest that 5% of low birth weight births in the case of PM₁₀ and 8% in the case of NO₂ could have been avoided with a reduction of 10 μg/m³ in the concentrations of these pollutants.

CONCLUSIONS

The impact of the results obtained- with 6105 cases attributable to PM₁₀ and up to 9385 cases attributable to NO₂ in a period of 9 study years- suggest the need to design structural and awareness public health measures to reduce air pollution in Spain.

Exposure to coarse particulate matter during gestation and term low birthweight in California: Variation in exposure and risk across region and socioeconomic subgroup

Despite evidence that particulate matter with an aerodynamic diameter ≤10 μm (PM₁₀) or ≤2.5 μm (PM_2.5) are associated with several adverse birth outcomes, research on the association between coarse particulate matter (PM_10-2.5) and birth outcomes is scarce, and results have been inconsistent. Furthermore, the literature is unclear whether associations between PM₁₀ and adverse birth outcomes were driven by PM_2.5 alone or also by PM_10-2.5 exposure. Research on the variation in exposure to and risk from PM_10-2.5 across populations is also needed to identify potentially vulnerable subgroups. We used birth certificate and ambient air monitoring data in California from 2002 to 2013 to develop a retrospective cohort study of pregnant women and their infants. Averaged gestational and trimester-specific exposures of PM_10-2.5 and PM_2.5 were calculated for mothers whose residential zip code tabulation areas were within a 20 km radius of monitors. We assessed the relationship between prenatal exposure to PM_10-2.5 and term low birthweight (TLBW) using logistic and linear regression, adjusting for maternal and paternal demographic, environmental, temporal, and health-related covariates. We also conducted analyses stratified by socioeconomic characteristics and regions. We found a relationship between PM_10-2.5 exposure during pregnancy and TLBW after controlling for PM_2.5 exposure: odds ratio for second quartile of exposure: 1.00 (95% confidence interval: 0.98, 1.03), third quartile: 1.03 (1.00, 1.06), fourth quartile: 1.04 (1.01, 1.07), compared to the first quartile. Associations were strong among Non-Hispanic Black mothers, mothers living in the Central Valley, and fathers without a college degree. Exposure to and risk from PM_10-2.5 were heterogeneous across California indicating environmental justice implications. We also found that paternal characteristics were associated with the risk of TLBW even after controlling for maternal characteristics. In addition to PM_10-2.5 total mass, further research is needed on the components of PM_10-2.5 which may be driving these associations.

Birth weight for gestational age and the risk of asthma in childhood and adolescence: a retrospective cohort study

OBJECTIVE

To examine the association between birth weight for gestational age and asthma in childhood and adolescence while controlling for potential confounders and considering smoking as an effect modifier.

METHODS

A retrospective cohort of all singleton term births in Nova Scotia, Canada, between 1989 and 1993 was identified in the provincial perinatal database and followed through 2014 by linking with administrative health data. The outcome, asthma, was defined as having one hospitalisation or two physician visits with an International Classification of Diseases code for asthma in a 2-year period. Birth weight was categorised as small (SGA), large (LGA) or appropriate (AGA) for gestational age. Multivariable-adjusted Cox proportional hazards models were used to examine the association between the birth weight for gestational age and asthma and to test for effect modification by maternal smoking in pregnancy.

RESULTS

Of the 40 724 cohort children, 10.5% and 11.7% were born SGA and LGA, respectively, and the risk of developing asthma to age 18 years was 30.2%. The adjusted HRs for SGA and LGA (relative to AGA) and asthma were 1.07 (95% CI 1.02 to 1.14) and 0.96 (95% CI 0.91 to 1.02), respectively. Relative to AGA children born to non-smoking mothers, SGA children were not at increased risk of asthma (HR 1.02), whereas both AGA and SGA children born to smoking mothers were at significantly increased risk (HR 1.14 and 1.29, respectively).

CONCLUSIONS

Our findings suggest that SGA in term infants is not associated with asthma in childhood in the absence of smoking in pregnancy.

Is preterm birth associated with asthma among children from birth to 17 years old? -A study based on 2011-2012 US National Survey of Children's Health

BACKGROUND

Preterm birth can interrupt lung development in utero and is associated with early life factors, which adversely affects the developing respiratory system. Studies on preterm birth and asthma risk are comparatively sparse and the results are not consistent.

METHODS

Multivariate analyses were performed on a cross-sectional data from the National Survey of Children's Health (NSCH) collected in 2011 to 2012. The NSCH was a nationally representative telephone survey sponsored by the Maternal and Child Health Bureau and conducted by the National Center for Health Statistics. A cross-sectional analysis using data from the US on 90,721 children was conducted to examine the relationship between preterm birth and asthma risk.

RESULTS

A total of 90,721 children under 17 years were included and 12% of the children were reported as preterm birth. The prevalence of diagnosed asthma was 15%, with a male to female ratio of 1.26:1. Children who were born preterm were 1.64 times (95% confidence interval: 1.45-1.84) more likely to develop asthma compared with those who were born term after controlling for confounders. Similarly, children who were low birth weight were 1.43 times (95% confidence interval: 1.25-1.63) more likely for asthma, and the odds ratio increased to 1.77 for those both preborn and low birth weight. Child's gender, race/ethnicity, age, family structure, family income levels, and household smoking were significantly associated with the odds of reported asthma.

CONCLUSIONS

Preterm birth was associated with increased risk of asthma among US children, supporting the notion that preterm birth may play a critical role in asthma development.

Temperature and Term Low Birth Weight in California

Few investigations have explored temperature and birth outcomes. In a retrospective cohort study, we examined apparent temperature, a combination of temperature and relative humidity, and term low birth weight (LBW) among 43,629 full-term LBW infants and 2,032,601 normal-weight infants in California (1999-2013). The California Department of Public Health provided birth certificate data, while meteorological data came from the California Irrigation Management Information System, US Environmental Protection Agency, and National Centers for Environmental Information. After considering several temperature metrics, we observed the best model fit for term LBW over the full gestation (per 10-degrees-Fahrenheit (°F) increase in apparent temperature, 13.0% change, 95% confidence interval: 4.1, 22.7) above 55°F, and the greatest association was for third-trimester exposure above 60°F (15.8%, 95% confidence interval: 5.0, 27.6). Apparent temperature during the first month of pregnancy exhibited no significant risk, while the first trimester had a significantly negative association, and second trimester, last month, and last 2 weeks had slightly increased risks. Mothers who were black or older, delivered male infants, or gave birth during the warm season had infants at the highest risks. This study provides further evidence for adverse birth outcomes from heat exposure for vulnerable subgroups of pregnant women.

Early Life Weight Gain and Development of Childhood Asthma in a Prospective Birth Cohort

RATIONALE

The prevalence of childhood asthma has been increasing worldwide in parallel with childhood obesity.

OBJECTIVES

We investigated whether there is a temporal relationship between early life weight gain (reflecting growth velocity) and early life body mass index (BMI) attained status (reflecting accumulative weight) with future risk of asthma in the Boston Birth Cohort.

METHODS

This report includes 1,928 children from the Boston Birth Cohort with a mean age of 7.8 years (standard deviation, 3.3 yr), enrolled at birth and followed prospectively. Asthma was defined using physician diagnosis code (International Classification of Diseases, Ninth Revision, Clinical Modification code 493.xx) in children 2 years and older. We categorized the children by their weight gain trajectory on the basis of changes in z-scores: slow (less than -0.67), on track (-0.67 to 0.67), rapid (0.67-1.28), and extremely rapid (>1.28); and by their BMI attained status (underweight, normal weight, and overweight) during the first 4, 12, and 24 months. Poisson regression models with robust variance estimation were applied to examine the relationship between early life weight gain/attained BMI and asthma.

RESULTS

During the first 4 months of life, 37% had on-track weight grain, 22% had slow weight gain, 15% had rapid weight gain, and 26% had extremely rapid weight gain. At 4 months, 61% were normal weight, 7% were underweight, and 32% were overweight. In adjusted analyses, extremely rapid early life weight gain during the first 4 and 24 months of life were each associated with increased risks of asthma (risk ratio, 1.34 for extremely rapid weight gain at 4 months; 95% confidence interval [CI], 1.06-1.70; risk ratio, 1.32 for extremely rapid weight gain at 24 months; 95% CI, 1.00-1.75) Similarly, overweight at 4, 12, and 24 months were each associated with an increased risk of asthma. Analyses that further adjusted for birthweight or preterm birth showed similar findings.

CONCLUSIONS

In this predominantly urban U.S. low-income minority birth cohort, excessive early life weight gain and overweight status were both associated with an increased risk of asthma in childhood.

Increased risk of asthma in overweight children born large for gestational age

BACKGROUND

Being born large for gestational age (LGA) is a marker of increased growth velocity in fetal life and a risk factor for childhood overweight. Both being born LGA and childhood overweight may influence the development of asthma, although the role of overweight in the association between LGA and childhood asthma is unclear. Importantly, recent studies have suggested that the association between overweight and asthma may be related to non-allergic pathways. If this also applies to the association between LGA and asthma, the association between being born LGA and asthma may be different for atopic and non-atopic children.

OBJECTIVE

We investigated the association of being LGA with the prevalence of asthma at age 8 in atopic and non-atopic children and the role of overweight in this association.

METHODS

Complete data on asthma, anthropometry and atopy at age of 8 years, and potential confounders were available for 1608 participants of the PIAMA birth cohort. Odds ratios for the association between LGA and asthma in atopic and non-atopic children were estimated by logistic regression analysis adjusting for potential confounders. Overweight was assessed as a potential modifier of the association between LGA and asthma.

RESULTS

Being born LGA was not significantly associated with asthma at age of 8 in atopic and non-atopic children. However, overweight at age of 8 years modified the association between asthma at age of 8 and LGA. In non-atopic children, children who were born LGA and were overweight at age of 8 years had a significantly increased odds of asthma compared to non-LGA, non-overweight children (adj OR 7.04; 95% CI 2.2-24).

CONCLUSIONS

We observed that non-atopic children born LGA, who were overweight by 8 years have an increased risk of asthma. If confirmed, these findings suggest that non-atopic children born LGA may be identified early in life as a high-risk group for asthma.

Estimation of disease burdens on preterm births and low birth weights attributable to maternal fine particulate matter exposure in Shanghai, China

BACKGROUND

Studies have shown that maternal exposure to particulate matter ≤2.5μm in aerodynamic diameter (PM_2.5) was associated with adverse birth outcomes such as preterm birth (PTB) and low birth weight (LBW). However, the burdens of PTB and LBW attributable to PM_2.5 were rarely evaluated, especially in developing countries.

OBJECTIVES

To estimate the burdens of PTBs and LBWs attributable to outdoor PM_2.5 in Shanghai, China.

METHODS

We collected annual-average PM_2.5 concentrations, concentration-response relationships between PM_2.5 exposure during pregnancy and PTBs and LBWs, rates of PTB and LBW, number of live births, and population sizes in grids of 10km×10km in Shanghai in 2013. Then, they were combined to estimate the odds ratios (ORs), relative risks (RRs), attributable fractions (AFs), and numbers of PTBs and LBWs associated with PM_2.5 exposure.

RESULTS

The population-weighted annual-average concentration of PM_2.5 in Shanghai was 56.19μg/m³ in 2013. According to the first-class limit of PM_2.5 (15μg/m³) in the Ambient Air Quality Standards of China, the weighted RRs of PTBs or LBWs associated with PM_2.5 in Shanghai were 1.49 [95% confidence interval (CI): 1.16-1.80] and 1.31 (95% CI: 1.04-1.67), respectively. There might be 32.61% (95% CI: 13.93%-44.42%) or 4160 (95% CI: 1778-5667) PTBs and 23.36% (95% CI: 3.86%-40.02%) or 1882 (95% CI: 311-3224) LBWs attributable to PM_2.5 exposure. The estimates varied appreciably among different districts of Shanghai.

CONCLUSIONS

Our analysis suggested that outdoor PM_2.5 air pollution might have led to considerable burdens of PTBs and LBWs in Shanghai, China.

Characteristics and respiratory risk profile of children aged less than 5 years presenting to an urban, Aboriginal-friendly, comprehensive primary health practice in Australia

AIM

There are no published data on factors impacting on acute respiratory illness (ARI) among urban Indigenous children. We describe the characteristics and respiratory risk profile of young urban Indigenous children attending an Aboriginal-friendly primary health-care practice.

METHODS

We conducted a cross-sectional analysis of data collected at baseline in a cohort study investigating ARI in urban Indigenous children aged less than 5 years registered with an Aboriginal primary health-care service. Descriptive analyses of epidemiological, clinical, environmental and cultural factors were performed. Logistic regression was undertaken to examine associations between child characteristics and the presence of ARI at baseline.

RESULTS

Between February 2013 and October 2015, 180 Indigenous children were enrolled; the median age was 18.4 months (7.7-35), 51% were male. A total of 40 (22%) children presented for a cough-related illness; however, ARI was identified in 33% of all children at the time of enrolment. A total of 72% of children were exposed to environmental tobacco smoke. ARI at baseline was associated with low birthweight (adjusted odds ratio (aOR) 2.54, 95% confidence interval (CI) 1.08-5.94), a history of eczema (aOR 2.67, 95% CI 1.00-7.15) and either having a family member from the Stolen Generation (aOR 3.47, 95% CI 1.33-9.03) or not knowing this family history (aOR 3.35, 95% CI 1.21-9.26).

CONCLUSIONS

We identified an urban community of children of high socio-economic disadvantage and who have excessive exposure to environmental tobacco smoke. Connection to the Stolen Generation or not knowing the family history may be directly impacting on child health in this community. Further research is needed to understand the relationship between cultural factors and ARI.

Preconception Blood Pressure and Risk of Low Birth Weight and Small for Gestational Age

Our objective was to examine whether high blood pressure in the preconception period was associated with low birth weight (LBW) and small-for-gestational age (SGA) in Chinese women. Data were obtained from the China–US Collaborative Project for Neural Tube Defects Prevention, a large population-based cohort study. We included 43 718 singleton live births delivered at gestational ages of 28−45 weeks to women who were registered before pregnancy in 7 counties in southern China. Blood pressure was measured during registration by trained healthcare workers, and other health-related information was recorded prospectively. We used logistic regression to evaluate the associations between preconception blood pressure and the risk of LBW and SGA, adjusting for potential confounders. The prevalence of hypertension in the preconception study population was 4.62% (2019/43 718). The incidences of LBW and SGA were 2.33% and 5.05% for the hypertension group and 2.01% and 5.68% for the nonhypertension group. Compared with the nonhypertension group, the hypertension group did not show significantly increased risk for LBW overall (adjusted risk ratio =1.16, 95% confidence interval 0.86−1.57) or SGA (adjusted risk ratio =0.89, 95% confidence interval 0.73−1.09). When participants with normal blood pressure were used as the reference, the adjusted risk ratio of SGA for prehypertensive women was 1.13 (95% confidence interval 1.03−1.25). Our results do not support an association between hypertension or higher blood pressure before pregnancy and increased risk of LBW or SGA.

Maternal body mass index before pregnancy is associated with increased bronchodilator dispensing in early childhood: A cross-sectional study

RATIONALE

Maternal prepregnancy obesity has been associated with early wheeze and childhood asthma in their offspring. Some of these studies have been in minority, urban, and disadvantaged populations using parental recall and questionnaires. The association of maternal prepregnancy obesity with bronchodilator dispensing to their offspring, in a primarily insured, non-urban, White population in the United States is unknown.

OBJECTIVES AND METHODS

We conducted a retrospective cohort study using pharmacy dispensing data from the electronic medical records of a large United States health maintenance organization to examine the relationship between maternal prepregnancy body mass index (BMI) and inhaled bronchodilator dispensing in the offspring to 4 years of age. We included infants ≥37 weeks' gestation with birth weight ≥2.5 kg which yielded 6,194 mother-baby pairs. Maternal prepregnancy BMI was categorized as underweight (<18.5 kg/m(2) ), normal (18.5-24.9 kg/m(2) ), overweight (25-29.9 kg/m(2) ), or obese (≥30 kg/m(2) ).

RESULTS

In the entire cohort, 27.6% of the offspring received a bronchodilator dispensing. This ranged from 19.2% in the offspring of underweight mothers to 31.3% of those born to obese mothers. In the fully adjusted model using normal BMI as the referent, children of obese mothers had a 22% higher rate of bronchodilator dispensing (adjusted OR = 1.22; 95%CI 1.05-1.41; P = 0.008).

CONCLUSIONS

In this insured, non-urban, White population, maternal prepregnancy obesity was associated with bronchodilator dispensing in the offspring in early life. These results extend previous data and reaffirm the potential widespread public health impact that prepregnancy obesity may have on subsequent childhood respiratory health. Pediatr Pulmonol. 2016;51:803-811. © 2016 Wiley Periodicals, Inc.

The Association between Birth Weight and Gestational Age and Asthma in 6-7- and 13-14-Year-Old Children

Background. Previous studies that assessed the role of birth weight and gestational age in the risk of asthma have been conflicting. Objectives. To examine the association between birth weight and gestational age and symptoms of asthma. Patients and Methods. Subjects were 6656 school children of ages 6-7 and 13-14 years from urban districts of Mazandaran, Iran. ISAAC questionnaires were used. Results. There was an increased risk of "wheeze ever" in both age groups with birth weight under 2.5 kg and in all subgroups of low birth weight (LBW). Birth weight more than 3.5 kg was associated with lower risk of "severe asthma" in age group 6-7 years. With respect to gestational age, higher risks of "wheeze ever," "asthma ever," and "night cough in the past 12 months" were found in age group 13-14 years born before 37 weeks and the risk of "severe asthma" was higher in younger group (6-7 years). A lower risk of "asthma ever" was also found in 6-7-year-old children and 13-14-year-old girls who were born after 40 weeks. Conclusions. This study showed that there is a direct relation between "wheeze ever" and LBW and an inverse relation between risk of "severe asthma" and birth weight more than 3.5 kg.

Incidence and characteristics of early childhood wheezing, Dhaka, Bangladesh, 2004-2010

BACKGROUND

Early childhood wheezing substantially impacts quality of life in high-income countries, but data are sparse on early childhood wheezing in low-income countries. We estimate wheezing incidence, describe wheezing phenotypes, and explore the contribution of respiratory viral illnesses among children aged <5 years in urban Bangladesh.

METHODS

During 2004-2010, respiratory illness surveillance was conducted through weekly home visits. Children with fever or respiratory illness were referred for examination by study physicians including lung auscultation. During 2005-2007, every fifth referred child had nasal washes tested for human metapneumovirus, respiratory syncytial viruses, and influenza and parainfluenza viruses.

RESULTS

During April 2004-July 2010, 23,609 children were enrolled in surveillance. Of these, 11,912 (50%) were male, median age at enrollment was 20 months (IQR 5-38), and 4,711 (20%) had ≥1 wheezing episode accounting for 8,901 episodes (733 [8%] associated with hospitalization); 25% wheezed at <1 year of age. Among children aged <5 years, incidences of wheezing and wheezing hospitalizations were 2,335/10,000 and 192/10,000 child-years. Twenty-eight percent had recurrent wheezing. Recurrent versus non-recurrent wheezing episodes were more likely to be associated with oxygen saturation <93% (OR 6.9, 95%CI 2.8-17.3), increased work of breathing (OR 1.6, 95%CI 1.4-1.8), and hospitalization (OR 2.0, 95%CI 1.6-2.4). Respiratory viruses were detected in 66% (578/873) of episodes with testing.

CONCLUSION

In urban Bangladesh, early childhood wheezing is common and largely associated with respiratory virus infections. Recurrent wheezing is associated with more severe illness and may predict children who would benefit most from closer follow-up and targeted interventions. Pediatr Pulmonol. 2016;51:588-595. © 2015 Wiley Periodicals, Inc.

Foetal and infant growth patterns, airway resistance and school-age asthma

BACKGROUND AND OBJECTIVE

Preterm birth, low birth weight and rapid infant weight gain are associated with increased risks of asthma symptoms in childhood. The underlying mechanism may include persistently higher airway resistance (Rint). The aim of our study was to examine the associations of longitudinally measured foetal and infant growth characteristics with Rint and asthma outcomes in school-age children.

METHODS

This study was embedded in a population-based prospective cohort study in Rotterdam, The Netherlands. Foetal growth was estimated by ultrasound in the second and third trimesters. Infant growth was measured at birth, 3, 6 and 12 months. At age 6 years, Rint was measured, and information about wheezing and asthma was obtained by questionnaires. The number of subjects per analysis differed per available outcome (3954-5066 subjects).

RESULTS

Longitudinal growth analyses showed that school-age children with increased Rint had lower foetal length growth and weight gain, and lower infant length growth. Children with persistent wheezing until age 6 years and physician-diagnosed asthma had a higher Rint compared with children who never wheezed or without asthma (difference z-scores Rint: 0.58 (0.19, 0.97) and 0.55 (0.15, 0.95), respectively).

CONCLUSION

Rint in school-age children is influenced by foetal growth restriction and is associated with asthma outcomes. See article, page 574.

Nocturnal dry cough in the first 7 years of life is associated with asthma at school age

BACKGROUND

Childhood wheeze is an important, well-known risk factor for asthma, yet little is known about the contribution of nocturnal dry cough. We investigated the association of nocturnal dry cough at ages 1-7 years with doctor-diagnosed asthma at 8 years of age, both in the presence and absence of wheeze.

METHODS

Data of 3,252 children from the PIAMA birth cohort were studied. Parents reported the presence of nocturnal dry cough, wheeze, and doctor-diagnosed asthma in the past 12 months yearly, from birth up to the age of 8 years.

RESULTS

Nocturnal dry cough without wheeze was significantly associated with doctor-diagnosed asthma at age 8, except for age 1 (range of Relative Risks (RR) at ages 2-7: 1.8 (age 5) - 7.1 (age 7), all P-values <0.048). As expected, wheeze without nocturnal dry cough was strongly associated with doctor-diagnosed asthma at age 8 (range of RR: 2.0 (age 1) - 22.2 (age 7), all P-values <0.003). Of interest, nocturnal dry cough with wheeze showed the strongest association with doctor-diagnosed asthma at age 8 (range of RR: 3.7 (age 1) - 26.0 (age 7), all P-values <0.001). The relative excess risk of asthma at age 8 due to interaction of nocturnal dry cough with wheeze at age 1 year was 1.8 (0.1-3.6, P < 0.01).

CONCLUSION

Nocturnal dry cough and wheeze in early childhood are both independently associated with asthma at school age. The presence of both nocturnal dry cough and wheeze at age 1 almost doubles the risk of asthma at age 8 compared to wheeze alone.

Epigenetic contributions to the developmental origins of adult lung disease

Perinatal insults, including intrauterine growth restriction, preterm birth, maternal exposure to toxins, or dietary deficiencies produce deviations in the epigenome of lung cells. Occurrence of perinatal insults often coincides with the final stages of lung development. The result of epigenome disruptions in response to perinatal insults during lung development may be long-term structural and functional impairment of the lung and development of lung disease. Understanding the contribution of epigenetic mechanisms to life-long lung disease following perinatal insults is the focus of the developmental origins of adult lung disease field. DNA methylation, histone modifications, and microRNA changes are all observed in various forms of lung disease. However, the perinatal contribution to such epigenetic mechanisms is poorly understood. Here we discuss the developmental origins of adult lung disease, the interplay between perinatal events, lung development and disease, and the role that epigenetic mechanisms play in connecting these events.

Influence of childhood growth on asthma and lung function in adolescence

Background

Low birth weight and rapid infant growth in early infancy are associated with increased risk of childhood asthma, but little is known about the role of postinfancy growth in asthmatic children.

Objectives

We sought to examine the associations of children's growth patterns with asthma, bronchial responsiveness, and lung function until adolescence.

Methods

Individual growth trajectories from birth until 10 years of age were estimated by using linear spline multilevel models for 9723 children participating in a population-based prospective cohort study. Current asthma at 8, 14, and 17 years of age was based on questionnaires. Lung function and bronchial responsiveness or reversibility were measured during clinic visits at 8 and 15 years of age.

Results

Rapid weight growth between 0 and 3 months of age was most consistently associated with increased risks of current asthma at the ages of 8 and 17 years, bronchial responsiveness at age 8 years, and bronchial reversibility at age 15 years. Rapid weight growth was associated with lung function values, with the strongest associations for weight gain between 3 and 7 years of age and higher forced vital capacity (FVC) and FEV₁ values at age 15 years (0.12 [95% CI, 0.08 to 0.17] and 0.11 [95% CI, 0.07 to 0.15], z score per SD, respectively) and weight growth between 0 and 3 months of age and lower FEV₁/FVC ratios at age 8 and 15 years (−0.13 [95% CI, −0.16 to −0.10] and −0.04 [95% CI, −0.07 to −0.01], z score per SD, respectively). Rapid length growth was associated with lower FVC and FVC₁ values at age 15 years.

Conclusion

Faster weight growth in early childhood is associated with asthma and bronchial hyperresponsiveness, and faster weight growth across childhood is associated with higher FVC and FEV₁ values.

Early origins of chronic obstructive lung diseases across the life course

Chronic obstructive lung diseases, like asthma and chronic obstructive pulmonary disease, have high prevalences and are a major public health concern. Chronic obstructive lung diseases have at least part of their origins in early life. Exposure to an adverse environment during critical periods in early life might lead to permanent developmental adaptations which results in impaired lung growth with smaller airways and lower lung volume, altered immunological responses and related inflammation, and subsequently to increased risks of chronic obstructive lung diseases throughout the life course. Various pathways leading from early life factors to respiratory health outcomes in later life have been studied, including fetal and early infant growth patterns, preterm birth, maternal obesity, diet and smoking, children's diet, allergen exposure and respiratory tract infections, and genetic susceptibility. Data on potential adverse factors in the embryonic and preconception period and respiratory health outcomes are scarce. Also, the underlying mechanisms how specific adverse exposures in the fetal and early postnatal period lead to chronic obstructive lung diseases in later life are not yet fully understood. Current studies suggest that interactions between early environmental exposures and genetic factors such as changes in DNA-methylation and RNA expression patterns may explain the early development of chronic obstructive lung diseases. New well-designed epidemiological studies are needed to identify specific critical periods and to elucidate the mechanisms underlying the development of chronic obstructive lung disease throughout the life course.

Sources and contents of air pollution affecting term low birth weight in Los Angeles County, California, 2001-2008

BACKGROUND

Low birth weight (LBW, <2500 g) has been associated with exposure to air pollution, but it is still unclear which sources or components of air pollution might be in play. The association between ultrafine particles and LBW has never been studied.

OBJECTIVES

To study the relationships between LBW in term born infants and exposure to particles by size fraction, source and chemical composition, and complementary components of air pollution in Los Angeles County (California, USA) over the period 2001-2008.

METHODS

Birth certificates (n=960,945) were geocoded to maternal residence. Primary particulate matter (PM) concentrations by source and composition were modeled. Measured fine PM, nitrogen dioxide and ozone concentrations were interpolated using empirical Bayesian kriging. Traffic indices were estimated. Associations between LBW and air pollution metrics were examined using generalized additive models, adjusting for maternal age, parity, race/ethnicity, education, neighborhood income, gestational age and infant sex.

RESULTS

Increased LBW risks were associated with the mass of primary fine and ultrafine PM, with several major sources (especially gasoline, wood burning and commercial meat cooking) of primary PM, and chemical species in primary PM (elemental and organic carbon, potassium, iron, chromium, nickel, and titanium but not lead or arsenic). Increased LBW risks were also associated with total fine PM mass, nitrogen dioxide and local traffic indices (especially within 50 m from home), but not with ozone. Stronger associations were observed in infants born to women with low socioeconomic status, chronic hypertension, diabetes and a high body mass index.

CONCLUSIONS

This study supports previously reported associations between traffic-related pollutants and LBW and suggests other pollution sources and components, including ultrafine particles, as possible risk factors.

Perinatal risk factors for wheezing phenotypes in the first 8 years of life

BACKGROUND

A novel data-driven approach was used to identify wheezing phenotypes in pre-schoolchildren aged 0-8 years, in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort. Five phenotypes were identified: never/infrequent wheeze, transient early wheeze, intermediate onset wheeze, persistent wheeze and late onset wheeze. It is unknown which perinatal risk factors drive development of these phenotypes.

OBJECTIVE

The objective of the study was to assess associations of perinatal factors with wheezing phenotypes and to identify possible targets for prevention.

METHODS

In the PIAMA study (n = 3963), perinatal factors were collected at 3 months, and wheezing was assessed annually until the age of 8 years. Associations between perinatal risk factors and the five wheezing phenotypes were assessed using weighted multinomial logistic regression models. Odds ratios were adjusted for confounding variables and calculated with 'never/infrequent wheeze' as reference category.

RESULTS

Complete data were available for 2728 children. Risk factors for transient early wheeze (n = 455) were male gender, maternal and paternal allergy, low maternal age, high maternal body mass index, short pregnancy duration, smoking during pregnancy, presence of older siblings and day-care attendance. Risk factors for persistent wheeze (n = 83) were male gender, maternal and paternal allergy, and not receiving breastfeeding for at least 12 weeks. Intermediate onset wheeze (n = 98) was associated with a lower birth weight and late onset wheeze (n = 45) with maternal allergy.

CONCLUSION AND CLINICAL RELEVANCE

We identified different risk factors for specific childhood wheezing phenotypes. Some of these are modifiable, such as maternal age and body mass index, smoking, day-care attendance and breastfeeding, and may be important targets for prevention programmes.

Perinatal exposure to solvents and wheezing, eczema and food allergies at age 2

OBJECTIVES

The time from the prenatal period through early childhood is an important window of vulnerability for the developing immune and respiratory systems, both sensitive to environmental chemicals such as solvents. This study sought to examine the effects of solvent exposure during the prenatal and postnatal periods on wheezing, eczema and food allergies in early childhood.

METHODS

This study, based on the PELAGIE cohort, included 1505 mother-child pairs with measurements of prenatal and postnatal solvent exposures and data on wheezing, eczema or food allergies. The maternal occupation reported at inclusion, in early pregnancy allowed us to define prenatal occupational solvent exposure (by three specific job-exposure matrices). Data on prenatal and postnatal domestic solvent exposure, that is exposure to products that contain solvents, were obtained from self-administered questionnaires, once at inclusion and again when the child was 2 years old. Outcome data was collected at the 2-year follow-up. Associations between exposures and outcomes were estimated by logistic regression models, after adjustment for potential confounders.

RESULTS

No association was observed between prenatal exposure to solvents and the outcomes studied. Postnatal exposure was associated with an increased risk of wheezing (OR=1.80 (95% CI 1.25 to 2.59)) which persisted after adjustment for prenatal exposure. No significant association was observed with eczema or food allergies.

CONCLUSIONS

Postnatal exposure to solvent-containing products in the home may increase the risk of wheezing in early childhood. Follow-up studies are needed to determine if the health effects observed at age 2 persist at later ages.

Low birth weight and environmental tobacco smoke increases the risk of wheezing in adolescents: a retrospective cohort study

Background

Low birth weight (LBW) and environmental tobacco smoke (ETS) exposure are each associated with wheezing in children. This study was designed to examine the combined association of LBW and ETS with wheezing.

Methods

A retrospective birth cohort analysis linked with a national survey of allergic disorders among 1,018,031 junior high school students in Taiwan (1995–1996) was analyzed. The reported incidence of wheezing (yes or no) and ETS exposure (4 categories: 0, 1–20, 21–40 and greater than or equal to 41 household cigarettes per day) were obtained from validated questionnaires. Multiple logistic regression models were used to assess the associations of interest.

Results

There were 844,003 (83%) subjects analyzed after the exclusion criteria. LBW was associated with an increased risk of reporting ever wheezing (odds ratio [OR] = 1.08, 95% confidence interval [CI] = 1.01–1.16), current wheezing (OR = 1.09, 95% CI = 1.00–1.20) and wheezing with exercise (OR = 1.11, 95% CI = 1.02–1.21) within the smoke-free cohort. Higher ETS exposure correlated to a higher risk of wheezing (ever, current and with exercise). With ETS exposure, adolescents from the lowest birth weight cohorts were more likely to report wheezing (ever, current and with exercise).

Conclusions

ETS and LBW each has been related to increasing public health risk for respiratory symptoms among adolescents. Furthermore, LBW may aggravate the risk among those exposed to ETS. LBW, ETS and associated respiratory impairments may deserve special attention as part of a comprehensive environmental health risk assessment directed toward prevention and intervention.

Birthweight and the risk of atopic diseases: the ISAAC Phase III study

BACKGROUND

The association between birthweight and asthma, eczema and rhinoconjunctivitisis conflicting.

AIMS

To examine the association between birthweight and symptoms of asthma, eczema and rhinoconjunctivitis.

METHODS

Parents or guardians of children aged 6–7 yr completed written questionnaires about symptoms of asthma, rhinoconjunctivitis and eczema, and several risk factors, including birthweight.

RESULTS

There were 162,324 children from 60 centres in 26 countries. Low birthweight(<2.5 kg) was associated with an increased risk of symptoms of asthma (current wheeze odds ratio = 1.20; 95% confidence interval = 1.12–1.30). Low birthweight was associated with a lower risk of eczema ever. Low birthweight was not associated with rhinoconjunctivitis. Large babies (birthweight ≥4.5 kg) were not associated with any of these outcomes.

CONCLUSIONS

This study has confirmed that low birthweight is a risk factor for symptoms of asthma, but not for rhinoconjunctivitis. The findings for eczema are equivocal.

Birth weight, gestational age, fetal growth and childhood asthma hospitalization

Background

Childhood asthma may have a fetal origin through fetal growth and development of the immunocompetence or respiratory organs.

Objective

We examined to which extent short gestational age, low birth weight and fetal growth restriction were associated with an increased risk of asthma hospitalization in childhood.

Methods

We undertook a cohort study based on several national registers in Denmark, Sweden and Finland. We included all live singleton born children in Denmark during 1979-2005 (N = 1,538,093), in Sweden during 1973-2004 (N = 3,067,670), and a 90% random sample of singleton children born in Finland during 1987-2004 (N = 1,050,744). The children were followed from three years of age to first hospitalization for asthma, emigration, death, their 18th birthday, or the end of study (the end of 2008 in Denmark, and the end of 2007 in Sweden or Finland), whichever came first. We computed the pseudo-values for each observation and used them in a generalized estimating equation to estimate relative risks (RR) for asthma hospitalization.

Results

A total of 131,783 children were hospitalized for asthma during follow-up. The risk for asthma hospitalization consistently increased with lower birth weight and shorter gestational age. A 1000-g decrease in birth weight corresponded to a RR of 1.17 (95% confidence interval (CI) 1.15-1.18). A one-week decrease in gestational age corresponded to a RR of 1.05 (95% CI 1.04-1.06). Small for gestational age was associated with an increased risk of asthma hospitalization in term but not in preterm born children.

Conclusions

Fetal growth and gestational age may play a direct or indirect causal role in the development of childhood asthma.

Preterm birth, infant weight gain, and childhood asthma risk: a meta-analysis of 147,000 European children

Background

Preterm birth, low birth weight, and infant catch-up growth seem associated with an increased risk of respiratory diseases in later life, but individual studies showed conflicting results.

Objectives

We performed an individual participant data meta-analysis for 147,252 children of 31 birth cohort studies to determine the associations of birth and infant growth characteristics with the risks of preschool wheezing (1-4 years) and school-age asthma (5-10 years).

Methods

First, we performed an adjusted 1-stage random-effect meta-analysis to assess the combined associations of gestational age, birth weight, and infant weight gain with childhood asthma. Second, we performed an adjusted 2-stage random-effect meta-analysis to assess the associations of preterm birth (gestational age <37 weeks) and low birth weight (<2500 g) with childhood asthma outcomes.

Results

Younger gestational age at birth and higher infant weight gain were independently associated with higher risks of preschool wheezing and school-age asthma (P < .05). The inverse associations of birth weight with childhood asthma were explained by gestational age at birth. Compared with term-born children with normal infant weight gain, we observed the highest risks of school-age asthma in children born preterm with high infant weight gain (odds ratio [OR], 4.47; 95% CI, 2.58-7.76). Preterm birth was positively associated with an increased risk of preschool wheezing (pooled odds ratio [pOR], 1.34; 95% CI, 1.25-1.43) and school-age asthma (pOR, 1.40; 95% CI, 1.18-1.67) independent of birth weight. Weaker effect estimates were observed for the associations of low birth weight adjusted for gestational age at birth with preschool wheezing (pOR, 1.10; 95% CI, 1.00-1.21) and school-age asthma (pOR, 1.13; 95% CI, 1.01-1.27).

Conclusion

Younger gestational age at birth and higher infant weight gain were associated with childhood asthma outcomes. The associations of lower birth weight with childhood asthma were largely explained by gestational age at birth.

Birth weight and subsequent risk of asthma: a systematic review and meta-analysis

BACKGROUND

Previous studies suggest that birth weight is related to later risk of asthma. However, few meta-analyses have investigated these associations. Therefore, we performed a meta-analysis with different classifications to further validate the relationship between birth weight and asthma.

METHODS

PubMed (1990-2013), ScienceDirect (1990-2013), EMBASE(1990-2013),EBSCO (1990-2013) and Springer (1990-2013) were searched for articles. The following MeSH terms were used: "birth weight", "fetal growth retardation", "intrauterine growth restriction", "asthma", "wheezing".

RESULTS

We included 18 studies with data from a total of over 90,000 children and adults. (1) Low birth weight (<2,500g) as compared with BW>2,500g and BW=2500-4000g was associated with increased risk of asthma (Children: OR, 1.28; 95% CI, 1.09-1.50, P<0.05; OR, 1.34; 95% CI, 1.13-1.60, P<0.05, Adults: OR, 1.25; 95% CI, 1.12-1.39, P<0.05; OR, 1.25; 95% CI, 1.12-1.40, P<0.05). (2) High birth weight (>4,000g) was not associated with the risk of asthma when BW<4,000g and BW=2500-4000g were used as the reference.

CONCLUSIONS

These results suggest that low birth weight (<2,500g) is associated with increased risk of asthma both in children and adults and may serve as a mediator between prenatal influences and later disease risk; but high birth weight (>4,000g) was not associated with increased risk of asthma.

Effects of fine particulate matter and its constituents on low birth weight among full-term infants in California

Relationships between prenatal exposure to fine particles (PM2.5) and birth weight have been observed previously. Few studies have investigated specific constituents of PM2.5, which may identify sources and major contributors of risk. We examined the effects of trimester and full gestational prenatal exposures to PM2.5 mass and 23 PM2.5 constituents on birth weight among 646,296 term births in California between 2000 and 2006. We used linear and logistic regression models to assess associations between exposures and birth weight and risk of low birth weight (LBW; <2500g), respectively. Models were adjusted for individual demographic characteristics, apparent temperature, month and year of birth, region, and socioeconomic indicators. Higher full gestational exposures to PM2.5 mass and several PM2.5 constituents were significantly associated with reductions in term birth weight. The largest reductions in birth weight were associated with exposure to vanadium, sulfur, sulfate, iron, elemental carbon, titanium, manganese, bromine, ammonium, zinc, and copper. Several of these PM2.5 constituents were associated with increased risk of term LBW. Reductions in birth weight were generally larger among younger mothers and varied by race/ethnicity. Exposure to specific constituents of PM2.5, especially traffic-related particles, sulfur constituents, and metals, were associated with decreased birth weight in California.

Prevalence and co-occurrence of parentally reported possible asthma and allergic manifestations in pre-school children

Background

The aim of this study was to make an in-depth analysis of the prevalence and co-occurrence in pre-school children of possible asthma and atopic manifestations.

Methods

In Sweden 74%-84% of preschool children, depending on age, attend municipality organised day-care centres. Parents of 5,886 children 1–6 years of age, sampled from day-care centres in 62 municipalities all over Sweden, responded to a postal questionnaire regarding symptoms indicating prevalent possible asthma, allergic rhinitis, eczema, and food, furred pet and pollen allergy and other data in their children. Possible asthma was defined as any of the four criteria wheezing four times or more during the last year, physician diagnosis and current wheezing, ever had asthma and current wheezing, and current use of inhalation steroids, all based on questionnaire responses.

Results

The overall prevalence of possible asthma was 8.9%, of eczema 21.7%, of rhinitis 8.1%, and of food allergy 6.6%. There was a highly significant co-occurrence between possible asthma and all atopic manifestations, 35.7% having any of the manifestations. Presence of pet allergy was the manifestation showing the closest co-occurrence with presence of possible asthma, presence of pollen allergy with presence of rhinitis, and presence of food allergy with presence of eczema. Assessed from plots of age-specific prevalence of possible asthma, rhinitis, eczema and food allergy, the prevalence of all manifestations increased from one to three years of age and then decreased, except for rhinitis where the prevalence increased until six years of age, indicating no specific ordered sequence.

Conclusions

Parentally reported possible asthma, eczema and food allergy had a curvilinear prevalence course across age with a maximum at age 3, while rhinitis prevalence increased consistently with age. Co-occurrence between possible asthma and atopic manifestations was common, and some combinations were more common than others, but there was no evidence of a specific ordered onset sequence.

Influence of maternal and cord blood C-reactive protein on childhood respiratory symptoms and eczema

BACKGROUND

Inflammatory processes during pregnancy might affect fetal lung development and immune responses. We examined the associations of maternal and cord blood C-reactive protein levels with respiratory symptoms and eczema in preschool children.

METHODS

This study was embedded in a population-based prospective cohort study of 4984 children. Generalized estimating equations were used to assess the effect of C-reactive protein levels on respiratory symptoms or eczema. C-reactive protein levels were measured during early pregnancy and at birth. Wheezing, lower respiratory tract infections, and eczema until the age of 4 yr were annually obtained by questionnaires.

RESULTS

Maternal C-reactive protein was not associated with the risks of wheezing and lower respiratory tract infections. Compared to children with maternal C-reactive protein in the lowest quarter, children in the highest quarter had increased risks of eczema OR 1.20 (1.03, 1.40). Compared to children with cord blood C-reactive protein lower than 0.20 mg/l, those with levels higher than 0.20 mg/l had increased risks of wheezing, OR 1.21 (1.07, 1.36), and lower respiratory tract infections, OR 1.21 (1.05, 1.39), but not of eczema.

CONCLUSIONS

Our results suggest that elevated maternal C-reactive protein in pregnancy is associated with a higher risk of eczema, and C-reactive protein in cord blood with a higher risk of wheezing and lower respiratory tract infections in the first 4 yrs.

Human rhinovirus and wheezing: short and long-term associations in children

OBJECTIVES

Human rhinoviruses (HRVs) have been suggested to play a role in the development of childhood wheezing. However, whether HRV is causally related to the development of wheezing or HRV-associated wheeze is merely an indicator of disease susceptibility is unclear. Our aim was to study the role of HRV during infancy in the development of lower respiratory disease during infancy and childhood.

METHODS

In a population-based birth cohort, during the 1st year of life, nose and throat swabs were collected on a monthly basis, regardless of any symptoms. Polymerase chain reaction was used to detect an extensive panel of respiratory pathogens. Lung function was measured before 2 months of age. Information on respiratory symptoms was collected by daily questionnaires and electronic patient files.

RESULTS

1425 samples were collected in 140 infants. Both the presence of (single or multiple) pathogens (HRV equal to other pathogens) and increased respiratory system resistance were significantly associated with lower respiratory symptoms during infancy. HRV presence during infancy was not associated with the risk of wheezing at age 4, but every HRV episode with wheezing increased the risk of wheezing at age 4 (odds ratio 1.9, 1.1-3.5). This association weakened after adjustment for lung function (odds ratio 1.4, 0.7-2.9).

CONCLUSIONS

HRV and other viruses are associated with lower respiratory symptoms during infancy, as well as a high presymptomatic respiratory system resistance. HRV presence during infancy is not associated with childhood wheezing, but wheeze during a HRV episode is an indicator of children at high risk for childhood wheeze, partly because of a reduced neonatal lung function.

Parental psychological distress during pregnancy and wheezing in preschool children: the Generation R Study

BACKGROUND

Maternal psychological distress during pregnancy might affect fetal lung development and subsequently predispose children to childhood asthma.

OBJECTIVE

We sought to assess the associations of maternal psychological distress during pregnancy with early childhood wheezing.

METHODS

We performed a population-based prospective cohort study among 4848 children. We assessed maternal and paternal psychological distress at the second trimester of gestation and 3 years after delivery and maternal psychological distress at 2 and 6 months after delivery by using the Brief Symptom Inventory questionnaire. Wheezing in the children was annually examined by using questionnaires from 1 to 4 years. Physician-diagnosed ever asthma was reported at 6 years.

RESULTS

Mothers with psychological distress during pregnancy had increased odds of wheezing in their children from 1 to 4 years of life (overall distress: odds ratio [OR], 1.60 [95% CI, 1.32-1.93]; depression: OR, 1.46 [95% CI, 1.20-1.77]; and anxiety: OR, 1.39 [95% CI, 1.15-1.67]). We observed similar positive associations with the number of wheezing episodes, wheezing patterns, and physician-diagnosed asthma at 6 years. Paternal distress during pregnancy and maternal and paternal distress after delivery did not affect these results and were not associated with childhood wheezing.

CONCLUSION

Maternal psychological distress during pregnancy is associated with increased odds of wheezing in their children during the first 6 years of life independent of paternal psychological distress during pregnancy and maternal and paternal psychological distress after delivery. These results suggest a possible intrauterine programming effect of maternal psychological distress leading to respiratory morbidity.

Perinatal factors and respiratory health in children

BACKGROUND

There is conflicting evidence regarding the associations between anthropometric birth measures and asthma and lung function in children, particularly for apparently healthy infants born at term.

OBJECTIVE

Our objective was to elucidate these relationships paying particular attention to features of study design and analysis that may threaten the validity of previous studies in this field.

METHODS

We analysed data from a cohort of children with a family history of asthma who were recruited antenatally. Anthropometric birth measures and potential confounders were recorded at birth and within the first year of life. Lung function and asthma outcomes were measured at 8 years of age. Airway hyperresponsiveness (AHR) was measured by methacholine challenge. The potential for a reversal paradox, due to inclusion of covariates on the causal pathway, was investigated.

RESULTS

Four hundred and fifty (73% of the initial cohort) children were tested at age 8 years. Birth weight in the lowest tertile was associated with current asthma (OR 1.95, 95% CI 1.08, 3.54) and recent wheeze (OR 1.87, 95%CI 1.08, 3.24), but not with AHR (OR 1.37, 95% CI 0.68, 2.78). Birth weight was positively associated with lung function. Current height modified the relationship between birth length and lung function suggesting that post-natal growth has an effect on this relationship.

CONCLUSIONS

Low birth weight is associated with a greater risk of current asthma and lower lung function at 8 years in children with a family history of asthma. Current height should be treated as an effect modifier when investigating the fetal origins hypothesis.

Fetal growth and risk of childhood asthma and allergic disease

Introduction

Early genetic and environmental factors have been discussed as potential causes for the high prevalence of asthma and allergic disease in the western world, and knowledge on fetal growth and its consequence on future health and disease development is emerging.

Objective

This review article is an attempt to summarize research on fetal growth and risk of asthma and allergic disease. Current knowledge and novel findings will be reviewed and open research questions identified, to give basic scientists, immunologists and clinicians an overview of an emerging research field.

Methods

PubMed-search on pre-defined terms and cross-references.

Results

Several studies have shown a correlation between low birth weight and/or gestational age and asthma and high birth weight and/or gestational age and atopy. The exact mechanism is not yet clear but both environmental and genetic factors seem to contribute to fetal growth. Some of these factors are confounders that can be adjusted for, and twin studies have been very helpful in this context. Suggested mechanisms behind fetal growth are often linked to the feto-maternal circulation, including the development of placenta and umbilical cord. However, the causal link between fetal growth restriction and subsequent asthma and allergic disease remains unexplained. New research regarding the catch-up growth following growth restriction has posited an alternative theory that diseases later on in life result from rapid catch-up growth rather than intrauterine growth restriction per se. Several studies have found a correlation between a rapid weight gain after birth and development of asthma or wheezing in childhood.

Conclusion and clinical relevance

Asthma and allergic disease are multifactorial. Several mechanisms seem to influence their development. Additional studies are needed before we fully understand the causal links between fetal growth and development of asthma and allergic diseases.

Predictors for asthma at age 7 years for low-income children enrolled in the Childhood Asthma Prevention Study

OBJECTIVE

To identify the predictive factors of early childhood wheezing in children of low socioeconomic status.

STUDY DESIGN

The Childhood Asthma Prevention Study enrolled 177 low-income children (9-24 months old) with frequent wheezing. At age 7 years, presence of asthma was assessed through caregiver reports of physician diagnosis of asthma (CRPDA) and corroborated by assessment of bronchial hyperresponsiveness (BHR). Lung function, inflammatory markers, and asthma symptom severity were compared for children with ±CRPDA, ±BHR, and asthma. Baseline predictors for CRPDA, BHR, and asthma at 7 years of age were examined.

RESULTS

Maternal symptom report strongly differentiated children with +CRPDA (49%) despite comparable airflow measurements (P < .0001), and spirometric lung function measurements were different for +BHR (65%) versus -BHR (P < .005). Univariate analyses revealed different baseline predictors of +CRPDA and +BHR for children at age 7 years. Higher levels of maternal psychological resources were associated with +CRPDA, but not +BHR. Only 39% of children with a history of frequent wheezing met the conservative definition of asthma at age 7 years, with the following significant predictors found: low birth weight, baseline symptom severity, and maternal psychological resources.

CONCLUSIONS

This low-income, multi-ethnic group of wheezing infants represents a unique population of children with distinct characteristics and risks for persistent asthma. Determination of asthma status at 7 years of age required objective measurement of BHR in addition to CRPDA. The association of maternal psychological resources with +CRPDA may represent a previously unrecognized factor in the determination of asthma status among low-income groups.

[Indoor air quality and adult asthma]

INTRODUCTION

Asthma is a chronic inflammatory disease of the airways. The recent increase in its global prevalence suggests a possible role of environmental factors such as indoor air pollution. In 2000, according to the Institute Of Medicine, there was insufficient evidence to determine whether or not an association existed between high priority indoor air pollutants, listed by the French Indoor Air Quality Observatory, and asthma. The objective of this paper is to describe the current state of knowledge on the links between exposure to high priority indoor air pollutants and exacerbations of adult asthma.

METHOD

A review of the Medline database has been undertaken of the following pollutants: formaldehyde, benzene, acetaldehyde, volatile organic compounds, particles (PM2.5, PM10) and diethylhexyl-phthalate. The studies were classified by type and source of pollutant.

RESULTS

Twenty-three studies were included in the analysis. Most of the observational studies have shown an association between pollutants (by type and source) and adult asthma. The best documented pollutants were formaldehyde and volatile organic compounds. No studies were found on acetaldehyde and diethylhexyl-phthalate.

CONCLUSION

The analysis of the literature is complicated on account of the difficulty of comparing different studies. However, since the synthesis performed in 2000, the existence of a link between chemical indoor air pollutants and increased respiratory symptoms appears to be reinforced. It seems necessary to adopt preventive health measures while pursuing scientific research on this topic.

Pooling birth cohorts in allergy and asthma: European Union-funded initiatives - a MeDALL, CHICOS, ENRIECO, and GA²LEN joint paper

Long-term birth cohort studies are essential to understanding the life course and childhood predictors of allergy and the complex interplay between genes and the environment (including lifestyle and socioeconomic determinants). Over 100 cohorts focusing on asthma and allergy have been initiated in the world over the past 30 years. Since 2004, several research initiatives funded under the EU Framework Program for Research and Technological Development FP6-FP7 have attempted to identify, compare, and evaluate pooling data from existing European birth cohorts (GA(2)LEN: Global Allergy and European Network, FP6; ENRIECO: Environmental Health Risks in European Birth Cohorts, FP7; CHICOS: Developing a Child Cohort Research Strategy for Europe, FP7; MeDALL: Mechanisms of the Development of ALLergy, FP7). However, there is a general lack of knowledge about these initiatives and their potentials. The aim of this paper is to review current and past EU-funded projects in order to make a summary of their goals and achievements and to suggest future research needs of these European birth cohort networks.

Population-based study on association between birth weight and risk of asthma: a propensity score approach

BACKGROUND

Previous studies that assessed the role of birth weight in the risk of asthma have been limited because of selection bias and covariate imbalance.

OBJECTIVE

To assess the association between birth weight and risk of asthma by applying a propensity score approach.

METHODS

The study was designed as a retrospective cohort study based on a birth cohort of children born between January 1, 1976, and December 31, 1979, in Rochester, Minnesota. The propensity scores for birth weight were formulated using 16 covariates. We matched the propensity scores for children having low birth weight (<2,500 g) within a caliper of 0.2 SD of logit function of propensity scores. We calculated the cumulative incidence of asthma between low and normal birth weight groups using the Kaplan-Meier curve.

RESULTS

There were 3933 eligible children born between January 1, 1976, and December 31, 1979. Before matching, 13 of the 193 children (6.7%) born weighing 2,500 g developed asthma, whereas 201 of the 3,740 children (5.4%) born weighing 2,500 g and above developed asthma (P=.42). There were significant covariate imbalances between comparison groups. However, after propensity score matching, covariate imbalance was significantly reduced, and children born weighing less than 2,500 g had a similar risk to matched children born with normal birth weight (8.3% vs 7.3%, P=.75).

CONCLUSION

Birth weight is not associated with risk of asthma during the first 6 years of life. The propensity score may be a useful method for observational studies concerning asthma epidemiology.

Obesity and pulmonary disease: unanswered questions

Obesity is associated with risk of pulmonary disease, and adversely affects lung function. The parallel increase in obesity and asthma suggests the two conditions are linked; indeed, they can worsen each other. Obesity and inadequate asthma control are associated with poor quality of life, and place a high economic burden on public health. Although the obesity-lung interaction is a major issue for basic research and clinical studies, various questions remain unanswered. Do intrauterine and early life factors impact on the development of obesity and lung disease? If so, can this be prevented? Asthma is generally more severe in obese subjects, but is adiposity a driver of a new asthma phenotype that features greater morbidity and mortality, worse control and decreased response to medications? Obese individuals have small lung volumes, hence their airway calibre is reduced and airway resistance is increased. What puzzles physicians is whether peripheral airways undergo remodelling, which would increase bronchoconstriction. Obese asthmatics respond suboptimally to anti-inflammatory treatment, which raises the question: 'what drug for what patient?' Life expectancy is decreased in obesity and in chronic pulmonary disorders, but does obesity protect against or trigger chronic obstructive pulmonary disease? The time has come to find answers to these questions.

A nationwide study of asthma incidence rate and its determinants in Swedish pre-school children

While many studies on asthma prevalence have been published, the number of studies on asthma incidence in pre-school children is limited. In this project, a nationwide sample of pre-school children was followed with the aim of estimating cumulative 5-year asthma incidence and its determinants. Parents of 5,886 children 1-6 years of age, sampled from day-care centres in 62 municipalities all over Sweden, responded in 2002 to a baseline postal questionnaire with questions regarding symptoms indicating possible asthma or atopic conditions, and a number of other variables. In 2007, parents of 4,255 children responded to an almost identical follow-up questionnaire. Of these, the 3,715 children who were free from asthma at baseline constitute the study population for this report. A large number of potential baseline determinants for cumulative 5-year asthma incidence were identified. Of these, food allergy, rhinitis, incomplete asthma diagnosis criteria (wheezing last 12 months, and ever had asthma but no current symptoms), parental rhinitis, parental asthma, age, and eczema, in ranking order of importance, remained significant in multivariate logistic regression analysis. The asthma incidence rate was highly dependent on presence or absence of these variables, the average annual rate ranging from 2/1,000/year in 6-year-olds with no determinants to 154/1,000/year in 1-year-olds with all determinants, corresponding to 11/1,000/year based on the whole study population.

Interaction of a 17q12 variant with both fetal and infant smoke exposure in the development of childhood asthma-like symptoms

BACKGROUND

Gene variants on chromosome 17q12-21 are associated with an increased risk of childhood-onset asthma, a risk known to be modified by environmental tobacco smoke (ETS).

OBJECTIVES

To assess whether the association of rs2305480 on chromosome 17q12 in the GSDML gene with asthma-like symptoms in the first 4 years of life is modified by smoke exposure during fetal and early postnatal life.

METHODS

We used data from two independent prospective cohort studies from fetal life onwards in the Netherlands. We genotyped rs2305480 and assessed maternal smoking during pregnancy and ETS exposure at the age of 2. Asthma-like symptoms, defined as any reported wheezing, shortness of breath or dry nocturnal cough, were reported by parents when the children were 1, 2, 3, and 4 years. Analyses were based on a total group of 4461 Caucasian children.

RESULTS

The G risk-allele of rs2305480 was associated with asthma-like symptoms [overall odds ratio 1.17 (1.11, 1.24), 2.66E-9]. The effect of rs2305480 on asthma-like symptoms was stronger among children who were exposed to smoke during fetal life (P-interaction = 0.04). Smoke exposure in early postnatal life was also associated with an increased effect of the 17q12 single nucleotide polymorphism (SNP) on asthma-like symptoms (P-interaction = 5.06E-4). These associations were consistent in both cohorts.

CONCLUSION

A 17q12 variant, rs2305480, was associated with asthma-like symptoms in preschool children, and this association was modified by smoke exposure already during fetal life, and in infancy. Further investigation regarding SNPs in linkage disequilibrium with rs2305480 in relation to pathophysiological pathways is needed.

Neonatal size in term children is associated with asthma at age 7, but not with atopic dermatitis or allergic sensitization

BACKGROUND

We hypothesized that anthropometrics in the newborn is associated with development of asthma later in life.

METHODS

The study included a prospective, longitudinal clinical study of a birth cohort of 411 Danish neonates born at term of mothers with a history of asthma. The primary endpoint was physician-diagnosed asthma at age 7 years. Allergic sensitization and atopic dermatitis (AD) were also investigated. Infant size was measured at the research clinic on four occasions during the first year of life. Risk for asthma, AD, and allergic sensitization at age 6-7 were estimated from logistic regression. Time to first asthma and AD were investigated by Cox regression. Multivariate models were adjusted for gender, gestational age, and mothers smoking during pregnancy.

RESULTS

Neonatal weight, length, body mass index and head circumference (z-score) were all significantly associated with asthma at age 7. Adjusted odds ratio for asthma by estimated birth weight z-score: 1.87 [1.23-2.84]; P = 0.004. Adjusted HR for onset of asthma by neonatal weight z-score: 1.46 [1.08-1.96]; P = 0.013. Neonatal size did not associate with AD or allergic sensitization.

CONCLUSIONS

Increased neonatal size was significantly associated with asthma at age 7 but not AD or allergic sensitization in at-risk children born at term. The findings suggest some common prenatal mechanisms linking body size and asthma.

Fetal and infant origins of asthma

Previous studies have suggested that asthma, like other common diseases, has at least part of its origin early in life. Low birth weight has been shown to be associated with increased risks of asthma, chronic obstructive airway disease, and impaired lung function in adults, and increased risks of respiratory symptoms in early childhood. The developmental plasticity hypothesis suggests that the associations between low birth weight and diseases in later life are explained by adaptation mechanisms in fetal life and infancy in response to various adverse exposures. Various pathways leading from adverse fetal and infant exposures to growth adaptations and respiratory health outcomes have been studied, including fetal and early infant growth patterns, maternal smoking and diet, children's diet, respiratory tract infections and acetaminophen use, and genetic susceptibility. Still, the specific adverse exposures in fetal and early postnatal life leading to respiratory disease in adult life are not yet fully understood. Current studies suggest that both environmental and genetic factors in various periods of life, and their epigenetic mechanisms may underlie the complex associations of low birth weight with respiratory disease in later life. New well-designed epidemiological studies are needed to identify the specific underlying mechanisms. This review is focused on specific adverse fetal and infant growth patterns and exposures, genetic susceptibility, possible respiratory adaptations and perspectives for new studies.