Birth weight and childhood wheezing disorders: a systematic review and meta-analysis

Birth weight and premature ovarian insufficiency: a systematic review and meta-analysis

OBJECTIVE

To comprehensively evaluate the effect of low birth weight on premature ovarian insufficiency.

METHODS

We performed a systematic review of the literature by searching MEDLINE, EMBASE, Web of Science, Scopus, Wanfang and CNKI up to August 2023. All cohort and case-control studies that included birth weight as an exposure and premature ovarian insufficiency as an outcome were included in the analysis. Data were combined using inverse-variance weighted meta-analysis with fixed and random effects models and between-study heterogeneity evaluated. We evaluated risk of bias using the Newcastle Ottawa Scale and using Egger's method to test publication bias. All statistical analyses were performed with the use of R software.

RESULTS

Five articles were included in the review. A total of 2,248,594 women were included, including 21,813 (1%) cases of premature ovarian insufficiency, 150,743 cases of low birth weight, and 220,703 cases of macrosomia. We found strong evidence that changed the results of the previous review that low birth weight is associated with an increased risk of premature ovarian insufficiency (OR = 1.15, 95%CI 1.09-1.22) in adulthood compared with normal birth weight. No effect of macrosomia on premature ovarian insufficiency was found.

CONCLUSIONS

Our meta-analysis showed strong evidence of an association between low birth weight and premature ovarian insufficiency. We should reduce the occurrence of low birth weight by various methods to avoid the occurrence of premature ovarian insufficiency.

Effects of size at birth on health, growth and developmental outcomes in children up to age 18: an umbrella review

BACKGROUND

Size at birth, an indicator of intrauterine growth, has been studied extensively in relation to subsequent health, growth and developmental outcomes. Our umbrella review synthesises evidence from systematic reviews and meta-analyses on the effects of size at birth on subsequent health, growth and development in children and adolescents up to age 18, and identifies gaps.

METHODS

We searched five databases from inception to mid-July 2021 to identify eligible systematic reviews and meta-analyses. For each meta-analysis, we extracted data on the exposures and outcomes measured and the strength of the association.

FINDINGS

We screened 16 641 articles and identified 302 systematic reviews. The literature operationalised size at birth (birth weight and/or gestation) in 12 ways. There were 1041 meta-analyses of associations between size at birth and 67 outcomes. Thirteen outcomes had no meta-analysis.Small size at birth was examined for 50 outcomes and was associated with over half of these (32 of 50); continuous/post-term/large size at birth was examined for 35 outcomes and was consistently associated with 11 of the 35 outcomes. Seventy-three meta-analyses (in 11 reviews) compared risks by size for gestational age (GA), stratified by preterm and term. Prematurity mechanisms were the key aetiologies linked to mortality and cognitive development, while intrauterine growth restriction (IUGR), manifesting as small for GA, was primarily linked to underweight and stunting.

INTERPRETATION

Future reviews should use methodologically sound comparators to further understand aetiological mechanisms linking IUGR and prematurity to subsequent outcomes. Future research should focus on understudied exposures (large size at birth and size at birth stratified by gestation), gaps in outcomes (specifically those without reviews or meta-analysis and stratified by age group of children) and neglected populations.

PROSPERO REGISTRATION NUMBER

CRD42021268843.

An Association Between Pediatric Bronchiolitis and Atopic Dermatitis: A Multi-Institutional Electronic Medical Records Database Study From Taiwan

Atopic dermatitis (AD) is triggered by many environmental factors. We sought to determine the relationship between birth weight, infectious diseases, and AD. This retrospective cohort study analyzed data from the CGR Database for the period 2004 through 2015 in Taiwan. All diseases were classified using the International Classification of Disease codes. Logistic regression adjusted for birth weights and comorbidities were analyzed by SAS (version 9.4). P < .05 were considered statistically significant. In children with AD, bronchiolitis was significantly associated with the development of AD, whether the patients were aged < 2 years (odds ratio [OR] = 1.497; P = .014) or ≥ 2 years (OR = 1.882; P = .022). There was also no difference in the association between AD and different birth weights. We conclude that AD is associated with a previous history of bronchiolitis in children, regardless of age (less than or greater than 2 years).

Prenatal Exposure to Heavy Metals and Adverse Birth Outcomes: Evidence From an E-Waste Area in China

Electronic waste that has not been properly treated can lead to environmental contamination including of heavy metals, which can pose risks to human health. Infants, a sensitive group, are highly susceptible to heavy metals exposure. The aim of this study was to investigate the association between prenatal heavy metal exposure and infant birth outcomes in an e-waste recycling area in China. We analyzed cadmium (Cd), chromium (Cr), manganese (Mn), lead (Pb), copper (Cu), and arsenic (As) concentrations in 102 human milk samples collected 4 weeks after delivery. The results showed that 34.3% of participants for Cr, which exceeds the World Health Organization (WHO) guidelines, as well as the mean exposure of Cr exceeded the WHO guidelines. We collected data on the birth weight (BW) and length of infants and analyzed the association between metal concentration in human milk and birth outcomes using multivariable linear regression. We observed a significant negative association between the Cd concentration in maternal milk and BW in female infants (β = -162.72, 95% CI = -303.16, -22.25). In contrast, heavy metals did not associate with birth outcomes in male infants. In this study, we found that 34.3% of participants in an e-waste recycling area had a Cr concentration that exceeded WHO guidelines, and there was a significant negative association between prenatal exposure to the Cd and infant BW in females. These results suggest that prenatal exposure to heavy metals in e-waste recycling areas may lead to adverse birth outcomes, especially for female infants.

Preterm birth, birth weight, infant weight gain and their associations with childhood asthma and spirometry: a cross-sectional observational study in Nairobi, Kenya

BACKGROUND

In sub-Saharan Africa, the origins of asthma and high prevalence of abnormal lung function remain unclear. In high-income countries (HICs), associations between birth measurements and childhood asthma and lung function highlight the importance of antenatal and early life factors in the aetiology of asthma and abnormal lung function in children. We present here the first study in sub-Saharan Africa to relate birth characteristics to both childhood respiratory symptoms and lung function.

METHODS

Children attending schools in two socioeconomically contrasting but geographically close areas of Nairobi, Kenya, were recruited to a cross-sectional study of childhood asthma and lung function. Questionnaires quantified respiratory symptoms and preterm birth; lung function was measured by spirometry; and parents were invited to bring the child's immunisation booklet containing records of birth weight and serial weights in the first year.

RESULTS

2373 children participated, 52% girls, median age (IQR), 10 years (8-13). Spirometry data were available for 1622. Child immunisation booklets were available for 500 and birth weight and infant weight gain data were available for 323 and 494 children, respectively. In multivariable analyses, preterm birth was associated with the childhood symptoms 'wheeze in the last 12 months'; OR 1.64, (95% CI 1.03 to 2.62), p=0.038; and 'trouble breathing' 3.18 (95% CI 2.27 to 4.45), p<0.001. Birth weight (kg) was associated with forced expiratory volume in 1 s z-score, regression coefficient (β) 0.30 (0.08, 0.52), p=0.008, FVC z-score 0.29 (95% CI 0.08 to 0.51); p=0.008 and restricted spirometry, OR 0.11 (95% CI 0.02 to 0.78), p=0.027.

CONCLUSION

These associations are in keeping with those in HICs and highlight antenatal factors in the aetiology of asthma and lung function abnormalities in sub-Saharan Africa.

Risk Factors and Age-Related Patterns of Asthma-Like Symptoms in Early Childhood

BACKGROUND

Episodes of asthma-like symptoms in young children are common, but little is known about risk factors and their patterns for the daily symptom burden.

OBJECTIVE

We investigated a variety of possible risk factors and their age-related impact on the number of asthma-like episodes during age 0 to 3 years.

METHODS

The study population included 700 children from the Copenhagen Prospective Studies on Asthma in Childhood2010 mother-child cohort followed prospectively from birth. Asthma-like symptoms were recorded until age 3 by daily diaries. Risk factors were analyzed by quasi-Poisson regressions, and interaction with age was explored.

RESULTS

Diary data were available in 662 children. Male sex, maternal asthma, low birth weight, maternal antibiotic use, high asthma exacerbation polygenic risk score, and high airway immune score were associated with a higher number of episodes in a multivariable analysis. Maternal asthma, preterm birth, caesarean section, and low birth weight showed an increasing impact with age, whereas sibling(s) at birth showed a decreased association with age. The remaining risk factors had a stable pattern during age 0 to 3 years. For every additional clinical risk factor (male sex, low birth weight, and maternal asthma) a child had, we found 34% more episodes (incidence rate ratio: 1.34, 95% confidence interval: 1.21-1.48; P < .001).

CONCLUSION

Using unique day-to-day diary recordings, we identified risk factors for the burden of asthma-like symptoms in the first 3 years of life and described their unique age-related patterns. This provides novel insight into the origin of asthma-like symptoms in early childhood that potentially pave a path for personalized prognostics and treatment.

Small vulnerable newborns-big potential for impact

Despite major achievements in child survival, the burden of neonatal mortality has remained high and even increased in some countries since 1990. Currently, most neonatal deaths are attributable to being born preterm, small for gestational age (SGA), or with low birthweight (LBW). Besides neonatal mortality, these conditions are associated with stillbirth and multiple morbidities, with short-term and long-term adverse consequences for the newborn, their families, and society, resulting in a major loss of human capital. Prevention of preterm birth, SGA, and LBW is thus critical for global child health and broader societal development. Progress has, however, been slow, largely because of the global community's failure to agree on the definition and magnitude of newborn vulnerability and best ways to address it, to frame the problem attractively, and to build a broad coalition of actors and a suitable governance structure to implement a change. We propose a new definition and a conceptual framework, bringing preterm birth, SGA, and LBW together under a broader umbrella term of the small vulnerable newborn (SVN). Adoption of the framework and the unified definition can facilitate improved problem definition and improved programming for SVN prevention. Interventions aiming at SVN prevention would result in a healthier start for live-born infants, while also reducing the number of stillbirths, improving maternal health, and contributing to a positive economic and social development in the society.

Improving birth weight measurement and recording practices in Kenya and Tanzania: a prospective intervention study with historical controls

BACKGROUND

Low birth weight (LBW) is a significant public health concern given its association with early-life mortality and other adverse health consequences that can impact the entire life cycle. In many countries, accurate estimates of LBW prevalence are lacking due to inaccuracies in collection and gaps in available data. Our study aimed to determine LBW prevalence among facility-born infants in selected areas of Kenya and Tanzania and to assess whether the introduction of an intervention to improve the accuracy of birth weight measurement would result in a meaningfully different estimate of LBW prevalence than current practice.

METHODS

We carried out a historically controlled intervention study in 22 health facilities in Kenya and three health facilities in Tanzania. The intervention included: provision of high-quality digital scales, training of nursing staff on accurate birth weight measurement, recording and scale calibration practices, and quality maintenance support that consisted of enhanced supervision and feedback (prospective arm). The historically controlled data were birth weights from the same facilities recorded in maternity registers for the same calendar months from the previous year measured using routine practices and manual scales. We calculated mean birth weight (95% confidence interval CI), mean difference in LBW prevalence, and respective risk ratio (95% CI) between study arms.

RESULTS

Between October 2019 and February 2020, we prospectively collected birth weights from 8441 newborns in Kenya and 4294 in Tanzania. Historical data were available from 9318 newborns in Kenya and 12,007 in Tanzania. In the prospective sample, the prevalence of LBW was 12.6% (95% confidence intervals [CI]: 10.9%-14.4%) in Kenya and 18.2% (12.2%-24.2%) in Tanzania. In the historical sample, the corresponding prevalence estimates were 7.8% (6.5%-9.2%) and 10.0% (8.6%-11.4%). Compared to the retrospective sample, the LBW prevalence in the prospective sample was 4.8% points (3.2%-6.4%) higher in Kenya and 8.2% points (2.3%-14.0%) higher in Tanzania, corresponding to a risk ratio of 1.61 (1.38-1.88) in Kenya and 1.81 (1.30-2.52) in Tanzania.

CONCLUSION

Routine birth weight records underestimate the risk of LBW among facility-born infants in Kenya and Tanzania. The quality of birth weight data can be improved by a simple intervention consisting of provision of digital scales and supportive training.

Risk of low birthweight associated with the timing and frequency of antenatal care visits in Lao PDR: a retrospective cohort study

BACKGROUND

Antenatal care (ANC) plays an important role in preventing low birthweight (LBW). Whereas the government of Lao People's Democratic Republic (Lao PDR) has committed to increasing the usage of ANC, little attention has been given to the early initiation of ANC. The present study assessed the influence of delayed and fewer ANC visits on LBW in the country.

METHODS

This is a retrospective cohort study conducted at Salavan Provincial Hospital. Study participants were all pregnant women who gave birth at the hospital between 1 August 2016 and 31 July 31 2017. Data were collected from medical records. Logistic regression analyses were performed to quantify the relationship between ANC visits and LBW. We also investigated factors associated with inadequate ANC visits: first ANC visit after the first trimester or < 4 ANC visits.

RESULTS

The mean birth weight was 2808.7 g [standard deviation: SD 455.6]. Among 1804 participants, 350 (19.4%) had babies with LBW, and 147 (8.2%) had inadequate ANC visits. In multivariate analyses, compared to participants with adequate ANC visits, those with ≥ 4 ANC visits and the first ANC visit after the second trimester, those with < 4 ANC visits, and those with no ANC visits had higher odds ratios (ORs) of LBW: 3.77 (95% confidence interval: CI = 1.66-8.57), 2.39 (95% CI = 1.18-4.83) and 2.22 (95% CI = 1.08-4.56), respectively. Younger maternal age (OR 1.42; 95% CI = 1.07-1.89), government subsidisation (OR 2.69; 95% CI = 1.97-3.68) and ethnic minority (OR 1.88; 95% CI = 1.50-2.34) were associated with increased risk of insufficient number of ANC visits after adjusting for covariates.

CONCLUSIONS

Frequent and early initiation of ANC was associated with a reduction in LBW in Lao PDR. Encouraging childbearing-aged women to receive sufficient ANC at proper timing may lead to a reduction in LBW and improvement in short- and long-term health outcomes of neonates. Special attention will be needed for ethnic minorities and women in lower socioeconomic classes.

Impact of biomass fuel smoke on respiratory health of children under 15 years old in Madagascar

BACKGROUND

Children exposed to biomass used in households are at risk to develop diseases or respiratory symptoms. In Madagascar more than 95% of households use it daily. The main objective is to study the impact of chronic exposure to biomass on respiratory health of children under 15 years old in Madagascar.

METHODS

Descriptive cross-sectional study conducted with questionnaires among urban and rural population of Antananarivo and Mahajanga provinces between 2016 and 2017. Variables were collected: number of hours spent in kitchen per day, respiratory symptoms and spirometric data. Categorized symptoms score and exposure index expressing chronic exposure to biomass were analyzed with multinomial logistic regression models.

RESULTS

Of the 661 children included in the analysis, 27.7% had 1 respiratory symptom and 29.3% had 2 or more respiratory symptoms. Moderate exposure index (aOR=1.57; CI95%=[1.30-1.89]; p<0.001) and high exposure index (aOR=1.76; CI95%=[1.39-2.24]; p<0.001) were significantly associated with 1 respiratory symptom, adjusted with provinces, household members and visitors smoking, perceived discomfort related to air pollution and birthweight. Exposure index was not significantly associated with an increased risk of having 2 or more respiratory symptoms (p = 0.754).

CONCLUSION

Respiratory symptoms were associated with exposure to biomass, living in coastal areas, birthweight, tobacco and perceived discomfort related to air pollution. Recommendations and actions must be implemented in order to improve respiratory health related to biomass among children.

Childhood overweight and obesity and abnormal birth anthropometric measures are associated with a higher prevalence of childhood asthma in pre-school age

OBJECTIVES

Childhood asthma is one of the most common non-communicable diseases in the world. Several perinatal and postnatal factors have been associated with increased risk of developing childhood asthma. The present study aims to assess whether childhood overweight and obesity and abnormal birth anthropometric measures affect the risk of developing childhood asthma in preschool age.

METHODS

In this study, 5215 preschool children at the age of 2-5 years were enrolled after applying several inclusion and exclusion criteria and they examined whether they present asthma symptoms. Non-adjusted and adjusted statistical analysis was performed to assess whether perinatal and postnatal factors increase the risk of developing childhood asthma.

RESULTS

A prevalence of 4.5% of childhood asthma was recorded. Among children diagnosed with asthma, 19.4% were affected by overweight and 13.9% were obese. Childhood overweight/obesity was indepedently associated with a 76% higher risk of childhood asthma than normal weight. Abnormal birth anthropometric measures, i.e. birth weight, length, and head circumference, were independently associated with higher odds (87%, 29%, and 23%, respectively) of childhood asthma than normal ranges.

CONCLUSIONS

This is a cross-sectional, nationally representative study which supported evidence that childhood overweight/obesity and abnormal birth anthropometric measures may independently increase the risk of childhood asthma in preschool age. Emergent health policies and strategies are recommended to promote a healthy lifestyle, preventing childhood obesity at the early stages of life.

Investigating the influence of breastfeeding on asthma in children under 12 years old in the UK Biobank

Background

Childhood-onset asthma (COA) has become a major and growing problem worldwide and imposes a heavy socioeconomic burden on individuals and families; therefore, understanding the influence of early-life experiences such as breastfeeding on COA is of great importance for early prevention.

Objectives

To investigate the impact of breastfeeding on asthma in children under 12 years of age and explore its role at two different stages of age in the UK Biobank cohort.

Methods

A total of 7,157 COA cases and 158,253 controls were obtained, with information regarding breastfeeding, COA, and other important variables available through questionnaires. The relationship between breastfeeding and COA were examined with the logistic regression while adjusting for available covariates. In addition, a sibling analysis was performed on 398 pairs of siblings to explain unmeasured family factors, and a genetic risk score analysis was performed to control for genetic confounding impact. Finally, a power evaluation was conducted in the sibling data.

Results

In the full cohort, it was identified that breastfeeding had a protective effect on COA (the adjusted odds ratio (OR)=0.875, 95% confidence intervals (CIs): 0.831~0.922; P=5.75×10^-7). The impact was slightly pronounced in children aged 6-12 years (OR=0.852, 95%CIs: 0.794~0.914, P=7.41×10^-6) compared to those aged under six years (OR=0.904, 95%CIs: 0.837~0.975, P=9.39×10^-3), although such difference was not substantial (P=0.266). However, in the sibling cohort these protective effects were no longer significant largely due to inadequate samples as it was demonstrated that the power was only 23.8% for all children in the sibling cohort under our current setting. The protective effect of breastfeeding on COA was nearly unchanged after incorporating the genetic risk score into both the full and sibling cohorts.

Conclusions

Our study offered supportive evidence for the protective effect of breastfeeding against asthma in children less than 12 years of age; however, sibling studies with larger samples were warranted to further validate the robustness our results against unmeasured family confounders. Our findings had the potential to encourage mothers to initiate and prolong breastfeeding.

Risk factors for current wheeze among school children (6–7 and 13–14 years old) in Khuzestan, Iran

Objectives

In recent years, there has been a clear trend of increasing allergic diseases especially in children, and developing countries are no exception. Thepresentstudy sought to determine the risk factors associated with wheezing among school children aged 6–7 and 13–14 years living in Khuzestan Province, Iran.

Study design

Cross-sectional.

Methods

Data for this cross-sectional study is the history of wheeze in the last 12 months. The participants included 6-7- and 13-14-year-old girls and boys studying in urban schools in Khuzestan Province in 2019. We collected the data using the multi stage sampling technique as suggested in the International Study of Asthma and Allergies in Childhood (ISAAC). The research reviewed the literature and consulted experts to collect the risk factors for demographic and clinical information, environmental exposure and lifestyle.

Results

Eight thousand questionnaires were handed out to both age groups, of which 7344 were completed. Two hundred ninety-nine (4.1 %) of the participants had current wheeze. Three-point four percent (124 individuals) in the 6–7 year age group and 4.8 % in the 13–14-year-old age group had current wheezing. The results of the logistic regression model suggest that the most significant risk factors associated with the chance of developing current wheeze in the both age groups are: being male (OR: 1.46, 95 % CI: 1.12–1.88), being from employed mother families (OR: 1.50, 95 %, CI:1.05–2.08), property ownership (OR:1.36, 95 %, CI:1.04–1.79) bugs in the property (OR: 1.29, 95 %, CI:0.99–1.70) mold in the property (OR: 1.75, 95 %, CI:1.12–2.76), pet(s) in the student's bedroom (OR: 1.75, 95 %, CI: 0.97–3.14), a family history of asthma and allergic diseases (OR: 2.20, 95 %, CI: 1.69–2.87), tobacco smoke exposures in the property (OR: 1.43, 95 %, CI:1.04–1.96), having allergic rhinitis (OR: 7.86, 95 % CI: 5.89–10.50) and eczema (OR: 3.85, 95 % CI: 2.10–7.08).

Conclusions

Families are suggested to adopt strategies to reduce exposure to outdoor air pollutants and contain indoor allergens. More studies are necessary to further explore the effects of modifying and changing these risk factors.

•

3.4 % in the 6–7 year age group and 4.8 % in the 13–14 year age group had current wheezing.

•

In both age groups, current wheeze is more common in boys than girls.

•

Mold in the home, pet in the bedroom and tobacco smoke exposures are the most important risk factors for current wheeze.

The effects of different parity and delivery mode on wheezing disorders in the children-a retrospective cohort study in Fujian, China

BACKGROUND

The relationship between childbirth delivery methods and the risk of wheezing in children remains controversial. Few studies have explored it under different maternal conditions.

OBJECTIVE

To explore the influence of childbirth delivery method on the onset of wheezing in children of different parity.

METHODS

A total of 21716 patients were included in this retrospective observational study. Multivariable logistic regression was used to analyze the relationship between childbirth delivery method and wheezing in children under 18 years of age in Fujian Province.

RESULTS

Wheezing differed statistically based on the child's sex, age, season of onset, parity, jaundice history, and feeding patterns (P < 0.05). After adjusting for confounding factors, in cases of parity greater than two, the risk of wheezing in cesarean section deliveries was higher than that in vaginal deliveries (OR: 1.107; 95% CI 1.010-1.214). In girls with parity greater than two (OR: 1.179; 95% CI 1.003-1.387) and normal-weight infants with parity greater than two (OR: 1.106; 95% CI 1.003-1.220), the risk of wheezing in cesarean section deliveries was higher. The interaction term between the mode of childbirth and parity was significant in girls (P = 0.014).

CONCLUSION

The method of childbirth delivery and parity are related to the risk of wheezing and may be relevant to gender and birth weight. Parity and gender have synergistic effects on wheezing.

National and subnational trends of birthweight in Peru: Pooled analysis of 2,927,761 births between 2012 and 2019 from the national birth registry

Background

National and subnational characterization of birthweight profiles lacks in low- and middle-income countries, yet these are needed for monitoring the progress of national and global nutritional targets. We aimed to describe birthweight indicators at the national and subnational levels in Peru (2012-2019), and by selected correlates.

Methods

We studied mean birthweight (g), low birthweight (<2,500 g) and small for gestational age (according to international growth curves) prevalences. We analysed the national birth registry and summarized the three birthweight indicators at the national, regional, and province level, also by geographic area (Coast, Highlands, and Amazon). With individual-level data from the mother, we described the birthweight indicators by age, educational level and healthcare provider. Following an ecological approach (province level), we described the birthweight indicators by human development index (HDI), altitude above sea level, proportion of the population living in poverty and proportion of rural population.

Findings

Mean birthweight was always the lowest in the Highlands (2,954 g in 2019) yet the highest in the Coast (3,516 g in 2019). The same was observed for low birthweight and small for gestational age. In regions with Coast and Highlands, the birthweight indicators worsen from the Coast to the Highlands; the largest absolute difference in mean birthweight between Coast and Highlands in the same region was 367 g. All birthweight indicators were the worst in mothers with none/initial education, while they improved with higher HDI.

Interpretation

This analysis suggests that interventions are needed at the province level, given the large differences observed between Coast and Highlands even in the same region.

Funding

Wellcome Trust (214185/Z/18/Z).

Exploring the association between adverse maternal circumstances and low birth weight in neonates: a nationwide population-based study in Bangladesh

OBJECTIVE

This study is concerned with helping to improve the health and care of newborn babies in Bangladesh by exploring adverse maternal circumstances and assessing whether these are contributing towards low birth weight (LBW) in neonates.

STUDY DESIGNS AND SETTINGS

Data were drawn and analysed from the Bangladesh Demographic and Health Survey, 2014. Any association between LBW and adverse maternal circumstances were assessed using a Chi-square test with determinants of LBW identified by multivariate logistic regression analysis.

PARTICIPANTS

The study is based on 4728 children aged below 5 years and born to women from selected households.

RESULTS

The rate of LBW was around 19.9% (199 per 1000 live births) with the highest level found in the Sylhet region (26.2%). The rate was even higher in rural areas (20.8%) and among illiterate mothers (26.6%). Several adverse maternal circumstances of the women included in the survey were found to be significant for increasing the likelihood of giving birth to LBW babies. These circumstances included the women being underweight (adjusted odds ratio (AOR) 1.26, 95% CI 1.06 to 1.49); having unwanted births (AOR 1.22, 95% CI 1.03 to 1.44); had previous pregnancies terminated (AOR 1.28, 95% CI 1.05 to 1.57); were victims of intimate partner violence (AOR 1.23, 95% CI 1.05 to 1.45) and taking antenatal care <4 times (AOR 1.23, 95% CI 1.03 to 1.48). Other important risk factors that were revealed included age at birth <18 years (AOR 1.42, 95% CI 1.11 to 1.83) and intervals between the number of births <24 months (AOR 1.25, 95% CI 1.01 to 1.55). When taking multiple fertility behaviours together such as, the ages of the women at birth (<18 years with interval <24 months (AOR 1.26, 95% CI 1.02 to 1.57) and birth order (>3 with interval <24 months (AOR 1.68, 95% CI 1.18 to 2.37), then the risk of having LBW babies significantly increased.

CONCLUSION

This study finds that adverse maternal circumstances combined with high-risk fertility behaviours are significantly associated with LBW in neonates. This situation could severely impede progress in Bangladesh towards achieving the sustainable development goal concerned with the healthcare of newborns.

Perinatal epidemiology: Issues, challenges, and potential solutions

Perinatal epidemiology research is concerned with identifying the effects of events during pregnancy on pregnancy outcomes that include maternal, fetal, and neonatal health outcomes. Randomized trials in perinatal research face many challenges, including randomization difficulties, ethical considerations, and inadequate statistical power due to the small number of subjects eligible for participation. For these reasons, most epidemiological studies conducted in this research field are observational and include different types of bias. This review describes the key methodological difficulties in the design and analysis of randomized and observational studies in perinatal epidemiology, and provides potential corrective approaches.

Chained Risk Assessment for Life-Long Disease Burden of Early Exposures - Demonstration of Concept Using Prenatal Maternal Smoking

Traditional risk factors and environmental exposures only explain less than half of the disease burden. The developmental origin of the health and disease (DOHaD) concept proposes that prenatal and early postnatal exposures increase disease susceptibility throughout life. The aim of this work is to demonstrate the application of the DOHaD concept in a chained risk assessment and to provide an estimate of later in life burden of disease related to maternal smoking. We conducted three systematic literature searches for meta-analysis and reviewed the literature reporting meta-analyses of long-term health outcomes associated with maternal smoking and intermediate risk factors (preterm birth, low birth weight, childhood overweight). In the chained model the three selected risk factors explained an additional 2% (34,000 DALY) of the total non-communicable disease burden (1.4 million DALY) in 2017. Being overweight in childhood was the most important risk factor (28,000 DALY). Maternal smoking was directly associated with 170 DALY and indirectly via the three intermediate risk factors 1000 DALY (1200 DALY in total). The results confirm the potential to explain a previously unattributed part of the non-communicable diseases by the DOHAD concept. It is likely that relevant outcomes are missing, resulting in an underestimation of disease burden.

Childhood Respiratory Risk Factor Profiles and Middle-Age Lung Function: A Prospective Cohort Study from the First to Sixth Decade

RATIONALE

Childhood risk factors for long-term lung health often coexist and their specific patterns may affect subsequent lung function differently.

OBJECTIVES

To identify childhood risk factor profiles and their influence on lung function and chronic obstructive pulmonary disease (COPD) in middle age, and potential pathways.

METHODS

Profiles of 11 childhood respiratory risk factors, documented at age 7, were identified in 8,352 participants from the Tasmanian Longitudinal Health Study using latent class analysis. We investigated associations between risk profiles and post-bronchodilator lung function and COPD at age 53, mediation by childhood lung function and adult asthma, and interaction with personal smoking.

RESULTS

Six risk profiles were identified: 1) unexposed or least exposed (49%); 2) parental smoking (21.5%); 3) allergy (10%); 4) frequent asthma, bronchitis (8.7%); 5) infrequent asthma, bronchitis (8.3%); and 6) frequent asthma, bronchitis, allergy (2.6%). Profile 6 was most strongly associated with lower forced expiratory volume in 1 second (FEV₁) (-261; 95% confidence interval, -373 to -148 ml); lower FEV₁/forced vital capacity (FVC) (-3.4; -4.8 to -1.9%) and increased COPD risk (odds ratio, 4.9; 2.1 to 11.0) at age 53. The effect of profile 6 on COPD was largely mediated by adult active asthma (62.5%) and reduced childhood lung function (26.5%). Profiles 2 and 4 had smaller adverse effects than profile 6. Notably, the effects of profiles 2 and 6 were synergistically stronger for smokers.

CONCLUSIONS

Profiles of childhood respiratory risk factors predict middle-age lung function levels and COPD risk. Specifically, children with frequent asthma attacks and allergies, especially if they also become adult smokers, are the most vulnerable group. Targeting active asthma in adulthood (i.e., a dominant mediator) and smoking (i.e., an effect modifier) may block causal pathways and lessen the effect of such established early-life exposures.

Preterm birth is associated with higher prevalence of wheeze and asthma in a selected population of Japanese children aged three years

BACKGROUND

The present cross-sectional study investigated the associations between low birthweight (LBW), high birthweight, preterm birth (PTB), postterm birth, small for gestational age (SGA), and large for gestational age (LGA) and the prevalence of wheeze and asthma in Japanese children aged three years (age range, 33-54 months; mean age, 38.7 months).

METHODS

Study subjects were 6364 children. A questionnaire was used to collect all data. Wheeze and asthma were defined according to the criteria of the International Study of Asthma and Allergies in Childhood.

RESULTS

The prevalence values of wheeze and asthma were 19.5% and 7.7%, respectively. Of the 6364 subjects, 8.8% were classified as LBW (<2500g), 90.4% as normal birthweight, 0.8% as high birthweight (≥4000g), 4.8% as PTB (<37 weeks), 94.8% as term birth, 0.4% as postterm birth (≥42 weeks), 7.8% as SGA (<10th percentile), 82.5% as appropriate for gestational age, and 9.7% as LGA (>90th percentile). Compared with term birth, PTB was independently positively associated with wheeze and asthma: the adjusted ORs (95% CI) were 1.47 (1.11-1.92) and 1.52 (1.02-2.20), respectively. An independent positive association was shown between PTB and wheeze only in boys; the interaction between PTB and sex was significant. Such an interaction between PTB and sex was not seen for asthma. No evident associations were observed between LBW, high birthweight, postterm birth, SGA, or LGA and wheeze or asthma.

CONCLUSIONS

This is the first study in Japan to show that PTB, but not LBW or SGA, was significantly positively associated with childhood wheeze and asthma.

The association between prenatal cadmium exposure and birth weight: A systematic review and meta-analysis of available evidence

We conducted a meta-analysis to evaluate the association between prenatal cadmium (Cd) exposure and birth weight. PubMed, Embase, China National Knowledge Infrastructure (CNKI), and Wanfang databases were searched for studies published before March 2019. We used a model-based method, standardizing effect size from linear regression models to include a maximum number of studies during our quantitative evaluations. As a result, 11 articles from the general population, containing 10 birth cohorts and one cross-sectional study, were included. Our meta-analysis demonstrated that a 50% increase of maternal urine Cd (UCd) would be associated with a 6.15 g decrease in neonatal birth weight (β = -6.15 g, 95% CI: -10.81, -1.49) as well as a 50% increase of maternal blood Cd (BCd) would be associated with an 11.57 g decrease (β = -11.57 g; 95% CI: -18.85, -4.30). Stratified analysis of UCd data indicated that the results of female newborns were statistically significant (β = -8.92 g, 95% CI: -17.51, -0.34), as was the first trimester (β = -11.34 g, 95% CI: -19.54, -3.14). Furthermore, increased UCd levels were associated with a higher rate of low birth weight (LBW) risk (OR = 1.12, 95% CI: 1.03, 1.22). This meta-analysis demonstrated that elevated maternal Cd levels are associated with decreased birth weight and higher LBW risk.

Birth weight is not causally associated with adult asthma: results from instrumental variable analyses

The association between lower birth weight and childhood asthma is well established. However, it remains unclear whether the influence of lower birth weight on asthma can persist into adulthood. We conducted a Mendelian randomization analysis to assess the causal relationship of birth weight (~140,000 individuals) on the risk of adult asthma (~62,000 individuals). We estimated the causal effect of birth weight to be 1.00 (95% CI 0.98~1.03, p = 0.737) using the genetic risk score method. We did not observe nonlinear relationship or gender difference for the estimated causal effect. With the inverse-variance weighted method, the causal effect of birth weight on adult asthma was estimated to be 1.02 (95% CI 0.84~1.24, p = 0.813). Additionally, the iMAP method provides no additional genome-wide evidence supporting the causal effects of birth weight on adult asthma. Our results were robust against various sensitivity analyses, and MR-PRESSO and MR-Egger regression showed that no instrument outliers and no horizontal pleiotropy were likely to bias the results. Overall, our study provides no evidence for the fetal origins of diseases hypothesis for adult asthma, implying that the impact of birth weight on asthma in years of children and adolescents does not persist into adult and previous findings may be biased by confounders.

Asthma, Rhinoconjunctivitis, Eczema, and the Association with Perinatal Anthropometric Factors in Vietnamese Children

Few studies have investigated possible causative and protective factors associated with allergic diseases in resource-limited countries, Southeast Asia. We estimated the current prevalence of asthma, rhinoconjunctivitis, and eczema among 6-year-old children, and identified anthropometric factors associated with asthma, rhinoconjunctivitis and eczema, in South-Central Vietnam. A birth cohort study recruited 1,999 children born at a provincial hospital in Nha Trang, Vietnam between May 2009 and May 2010. A 6-year follow-up survey was conducted where clinical, familial, and environmental information was collected by interviewing caregivers using a standardized form based on the International Study of Asthma and Allergies in Childhood, Phase Three Core and Environmental Questionnaire for 6–7-year-old children. The odds ratios of asthma, rhinoconjunctivitis, and eczema for anthropometric factors were estimated using logistic regression analysis. In total, 1202 children participated in the follow-up survey. The proportions of children who had current asthma, rhinoconjunctivitis, and eczema were 5.1% (95% confidence interval [CI] 3.9–6.5%), 11.5% (9.7–13.4%), and 6.7% (5.3–8.2%), respectively. Low birthweight (adjusted odds ratio 5.12, 95% CI 1.92–13.64) was independently associated with increased risk of eczema. Further studies are necessary to understand the involved mechanism.

Pregnancy and perinatal conditions and atopic disease prevalence in childhood and adulthood

BACKGROUND

Previous studies showed controversial results for the influence of pregnancy-related and perinatal factors on subsequent respiratory and atopic diseases in children. The aim of this study was to assess the association between perinatal variables and the prevalence of asthma, bronchial hyperreactivity (BHR), flexural eczema (FE), allergic rhinitis, and sensitization in childhood and early adulthood.

METHODS

The studied population was first examined in Munich and Dresden in 1995/1996 at age 9-11 years. Participants were followed until age 19-24 years using questionnaires and clinical examinations. Associations between perinatal data and subsequent atopic diseases were examined using logistic regression analyses adjusting for potential confounders.

RESULTS

Cesarean section was statistically significantly associated with BHR in early adulthood (odds ratio 4.8 [95% confidence interval 1.5-15.2]), while assisted birth was associated with presence of asthma symptoms in childhood (2.2 [1.2-3.9]), FE symptoms (2.2 [1.2-4.3]) and doctor's diagnosis of atopic dermatitis (1.9 [1.0-3.4]) in childhood, and sensitization in early adulthood (2.2 [1.1-4.3]). Lower birth length (1.9 [1.1-3.2]), lower birthweight (0.5 [0.3-0.9]), and higher birthweight (0.6 [0.4-1.0]) were predictive of sensitization in early adulthood compared to average birth length and birthweight, respectively. None of the other perinatal factors showed statistically significant associations with the outcomes.

CONCLUSIONS

Our results indicate that children who are born by cesarean section and especially by assisted birth, might be at greater risk for developing asthma, FE, and sensitization and should hence be monitored. Prenatal maternal stress might partly explain these associations, which should be further investigated.

Hospital admissions for lower respiratory tract infections in children born moderately/late preterm

OBJECTIVE

To evaluate the frequency and predictors of hospital admissions for lower respiratory tract infections (LRTIs) in moderately preterm (MP, 32⁺⁰ to 33⁺⁶ weeks) and late preterm (LP, 34⁺⁰ to 36⁺⁶ weeks) infants compared to term (T ≥37 weeks) and very preterm (VP, <32⁺⁰ weeks) infants.

STUDY DESIGN

This national register-based study covered all infants born in Finland in 1991-2008. Data on 1 018 256 infants were analyzed in four gestational age-based groups: VP (n = 6329), MP (n = 6796), LP (n = 39 928), and T (n = 965 203) groups. Data on hospital admissions due to bronchiolitis/bronchitis and pneumonia were collected up to the age of 7 years.

RESULTS

Hospital admissions for LRTIs were more common in the MP and LP groups than in the T group but less frequent than in the VP group: bronchiolitis/bronchitis (VP 24.4%, MP 13.9%, LP 9.5%, and T 5.6%) and pneumonia (VP 8.8%, MP 4.5%, LP 3.3%, and T 2.4%). Compared to the term group, MP and LP birth predicted bronchiolitis/bronchitis (MP OR 1.89; 95%CI 1.75-2.03, LP 1.51; 1.45-1.56) and pneumonia (MP 1.49; 1.32-1.67, LP 1.25; 1.18-1.33) admissions. Statistically significant risk factors for LRTIs included maternal smoking, cesarean section, male sex, admission to a neonatal unit and ventilator therapy. In addition, being first-born, being born SGA and neonatal antibiotic therapy were associated with bronchiolitis/bronchitis.

CONCLUSIONS

MP and LP births, in addition to VP birth, have a significant impact on respiratory infectious morbidity and the need of hospital admissions for LRTIs.

Pre-birth origins of allergy and asthma

Allergy is a chronic disease that can develop as early as infancy, suggesting that early life factors are important in its aetiology. Variable associations between size at birth, a crude marker of the fetal environment, and allergy have been reported in humans and require comprehensive review. Associations between birth weight and allergy are however confounded in humans, and we and others have therefore begun exploring the effects of early life events on allergy in experimental models. In particular, we are using ovine models to investigate whether and how a restricted environment before birth protects against allergy, whether methyl donor availability contributes to allergic protection in IUGR, and why maternal asthma during pregnancy is associated with increased risks of allergic disease in children. We found that experimental intrauterine growth restriction (IUGR) in sheep reduced cutaneous responses to antigens in progeny, despite normal or elevated IgE responses. Furthermore, maternal methyl donor supplementation in late pregnancy partially reversed effects of experimental IUGR, consistent with the proposal that epigenetic pathways underlie some but not all effects of IUGR on allergic susceptibility. Ovine experimental allergic asthma with exacerbations reduces relative fetal size in late gestation, with some changes in immune populations in fetal thymus suggestive of increased activation. Maternal allergic asthma in mice also predisposes progeny to allergy development. In conclusion, these findings in experimental models provide direct evidence that a perturbed environment before birth alters immune system development and postnatal function, and provide opportunities to investigate underlying mechanisms and develop and evaluate interventions.

Preterm birth and low birth weight continue to increase the risk of asthma from age 7 to 43

BACKGROUND

Perinatal events can influence the development of asthma in childhood but current evidence is contradictory concerning the effects on life-time asthma risk.

OBJECTIVE

To assess the relationship between birth characteristics and asthma from childhood to adulthood.

METHODOLOGY

All available birth records for the Tasmanian Longitudinal Health Study (TAHS) cohort, born in 1961 were obtained from the Tasmanian State Archives and Tasmanian hospitals. Low birth weight (LBW) was defined as less than 2500 grams. Preterm birth was defined as delivery before 37 weeks' gestation. Small for gestational age (SGA) was defined as a birth weight below the 10^th percentile for a given gestational age. Multivariate logistic and cox regression were used to examine associations between birth characteristics and lifetime risk of current and incident asthma, adjusting for confounders.

RESULTS

The prevalence of LBW was 5.2%, SGA was 13.8% and preterm was 3.3%. LBW (OR = 1.65, 95%CI 1.12,2.44) and preterm birth (OR = 1.81, 95%CI 0.99, 3.31) were both associated with an increased risk of current asthma between the ages of 7 to 43 years. There was no association between SGA and current asthma risk. However, SGA was associated with incident asthma (HR = 1.32, 95%CI 1.00, 1.74), and there was an interaction with sex (p value = 0.08), with males having a greater risk of incident asthma (HR = 1.70, 95%CI 1.16-2.49) than females (HR = 1.04, 95%CI 0.70-1.54).

CONCLUSIONS

Preterm birth and LBW were associated with an increased risk of current asthma into middle-age. These findings are the first to demonstrate the continuing impact of these characteristics on asthma risk into middle-age.

Birth weight in relation to health and disease in later life: an umbrella review of systematic reviews and meta-analyses

BACKGROUND

Birth weight, a marker of the intrauterine environment, has been extensively studied in epidemiological research in relation to subsequent health and disease. Although numerous meta-analyses have been published examining the association between birth weight and subsequent health-related outcomes, the epidemiological credibility of these associations has not been thoroughly assessed. The objective of this study is to map the diverse health outcomes associated with birth weight and evaluate the credibility and presence of biases in the reported associations.

METHODS

An umbrella review was performed to identify systematic reviews and meta-analyses of observational studies investigating the association between birth weight and subsequent health outcomes and traits. For each association, we estimated the summary effect size by random-effects and fixed-effects models, the 95 % confidence interval, and the 95 % prediction interval. We also assessed the between-study heterogeneity, evidence for small-study effects and excess significance bias. We further applied standardized methodological criteria to evaluate the epidemiological credibility of the statistically significant associations.

RESULTS

Thirty-nine articles including 78 associations between birth weight and diverse outcomes met the eligibility criteria. A wide range of health outcomes has been studied, ranging from anthropometry and metabolic diseases, cardiovascular diseases and cardiovascular risk factors, various cancers, respiratory diseases and allergies, musculoskeletal traits and perinatal outcomes. Forty-seven of 78 associations presented a nominally significant summary effect and 21 associations remained statistically significant at P < 1 × 10^-6. Thirty associations presented large or very large between-study heterogeneity. Evidence for small-study effects and excess significance bias was present in 13 and 16 associations, respectively. One association with low birth weight (increased risk for all-cause mortality), two dose-response associations with birth weight (higher bone mineral concentration in hip and lower risk for mortality from cardiovascular diseases per 1 kg increase in birth weight) and one association with small-for-gestational age infants with normal birth weight (increased risk for childhood stunting) presented convincing evidence. Eleven additional associations had highly suggestive evidence.

CONCLUSIONS

The range of outcomes convincingly associated with birth weight might be narrower than originally described under the "fetal origin hypothesis" of disease. There is weak evidence that birth weight constitutes an effective public health intervention marker.

In utero exposure to 25-hydroxyvitamin D and risk of childhood asthma, wheeze, and respiratory tract infections: A meta-analysis of birth cohort studies

BACKGROUND

Studies of the associations between in utero 25-hydroxyvitamin D (25[OH]D) exposure and risk of childhood asthma, wheeze, and respiratory tract infections are inconsistent and inconclusive.

OBJECTIVES

We sought to assess associations between 25(OH)D levels in cord blood or maternal venous blood and risk of offspring's asthma, wheeze, and respiratory tract infections.

METHODS

Data were derived from PubMed, Embase, Google Scholar, references from relevant articles, and de novo results from published studies until December 2015. A random-effects meta-analysis was conducted among 16 birth cohort studies.

RESULTS

Comparing the highest with the lowest category of 25(OH)D levels, the pooled odds ratios were 0.84 (95% CI, 0.70-1.01; P = .064) for asthma, 0.77 (95% CI, 0.58-1.03; P = .083) for wheeze, and 0.85 (95% CI, 0.66-1.09; P = .187) for respiratory tract infections. The observed inverse association for wheeze was more pronounced and became statistically significant in the studies that measured 25(OH)D levels in cord blood (0.43; 95% CI, 0.29-0.62; P < .001).

CONCLUSIONS

Accumulated evidence generated from this meta-analysis suggests that increased in utero exposure to 25(OH)D is inversely associated with the risk of asthma and wheeze during childhood. These findings are in keeping with the results of 2 recently published randomized clinical trials of vitamin D supplementation during pregnancy.

Longitudinal study of maternal body mass index, gestational weight gain, and offspring asthma

BACKGROUND

Sparse data are available on the relationship between prenatal exposures and asthma during later childhood. In a longitudinal study of adolescents and their mothers, we examined the association of (i) maternal prepregnancy body mass index (BMI) and (ii) gestational weight gain (GWG), with incidence of allergic and nonallergic asthma in offspring.

METHODS

Analyses were conducted using data from 12 963 children aged 9-14 years at enrolment in the Growing Up Today Study, and their mothers, who are participants in the Nurses' Health Study II. Physician-diagnosed asthma and allergies were assessed by questionnaires sent regularly to participants and their mothers. Logistic regression was used to evaluate associations of maternal BMI and GWG with offspring asthma, overall and by subtype.

RESULTS

Physician-diagnosed asthma during childhood or adolescence was reported by 2694 children (21%). Maternal prepregnancy overweight (OR: 1.19, 95% CI: 1.03-1.38) and obesity (1.34, 1.08-1.68) were associated with offspring asthma. In asthma subtype analyses, the association was seen only for asthma onset before age 12 years. Moreover, the association of maternal obesity with nonallergic asthma was observed in boys (2.39, 1.40-4.09) and not in girls (0.96, 0.50-1.85; Pinteraction = 0.03); the opposite pattern was suggested for allergic asthma. With regard to GWG, an association was suggested between gains of <15 lb and higher risk of offspring asthma (1.28, 0.98-1.66), without clear allergy- or sex-related patterns.

CONCLUSION

The relation of several prenatal factors to risk of childhood asthma supports the early origins hypothesis for asthma. The observed allergy- and sex-specific patterns suggest multiple etiologic pathways.

Maternal age and asthma in Latino populations

BACKGROUND

Younger maternal age at birth is associated with increased risk of asthma in offspring in European descent populations, but has not been studied in Latino populations.

OBJECTIVES

We sought to examine the relationship between maternal age at birth and prevalence of asthma in a nationwide study of Latino children.

METHODS

We included 3473 Latino children aged 8-21 years (1696 subjects with physician-diagnosed asthma and 1777 healthy controls) from five US centres and Puerto Rico recruited from July 2008 through November 2011. We used multiple logistic regression models to examine the effect of maternal age at birth on asthma in offspring overall and in analyses stratified by ethnic subgroup (Mexican American, Puerto Rican and other Latino). Secondary analyses evaluated the effects of siblings, acculturation and income on this relationship.

RESULTS

Maternal age < 20 years was significantly associated with decreased odds of asthma in offspring, independent of other risk factors (OR = 0.73, 95% CI: 0.57-0.93). In subgroup analyses, the protective effect of younger maternal age was observed only in Mexican Americans (OR = 0.53, 95% CI: 0.36, 0.79). In Puerto Ricans, older maternal age was associated with decreased odds of asthma (OR = 0.65, 95% CI: 0.44-0.97). In further stratified models, the protective effect of younger maternal age in Mexican Americans was seen only in children without older siblings (OR = 0.44, 95% CI: 0.23-0.81).

CONCLUSION AND CLINICAL RELEVANCE

In contrast to European descent populations, younger maternal age was associated with decreased odds of asthma in offspring in Mexican American women. Asthma is common in urban minority populations but the factors underlying the varying prevalence among different Latino ethnicities in the United States is not well understood. Maternal age represents one factor that may help to explain this variability.

In utero Programming of Allergic Susceptibility

BACKGROUND

Around 30-40% of the world's population will experience allergy, the most common and earliest-onset noncommunicable disease. With a steady rise in the incidence of allergic disease over recent decades, up to 18% of children will suffer a respiratory, food or skin allergy before their 18th birthday. There is compelling evidence that the risk of developing allergy is influenced by early life events and particularly in utero exposures.

METHODS

A comprehensive literature review was undertaken which outlines prenatal risk factors and potential mechanisms underlying the development of allergy in childhood.

RESULTS

Exposures including maternal cigarette smoking, preterm birth and Caesarean delivery are implicated in predisposing infants to the later development of allergy. In contrast, restricted growth in utero, a healthy maternal diet and a larger family size are protective, but the mechanisms here are unclear and require further investigation.

CONCLUSION

To ameliorate the allergy pandemic in young children, we must define prenatal mechanisms that alter the programming of the fetal immune system and also identify specific targets for antenatal interventions.

Gestational Age, Birthweight for Gestational Age, and Childhood Hospitalisations for Asthma and Other Wheezing Disorders

BACKGROUND

Preterm birth, early term birth, and low birthweight are associated with childhood wheezing disorders in developed Western settings, but observed associations could be confounded by socio-economic position. This study aims to clarify such associations in a developed non-Western setting with a different confounding structure.

METHODS

Using Cox regression, we examined the adjusted associations of gestational age and birthweight for gestational age with time to first public hospital admission for asthma, bronchitis, and bronchiolitis (International Classification of Diseases, Ninth Version Clinical Modification 466, 490, and 493) from 9 days to 12 years in a population-representative birth cohort of 8327 Chinese children in Hong Kong, a developed setting with less clear social patterning of prematurity or birthweight. Analyses were adjusted for infant and parental characteristics and socio-economic position.

RESULTS

Children born late preterm (34 to <37 weeks) had higher risk of hospitalisation for asthma and other wheezing disorders [hazard ratio (HR) 1.99, 95% confidence interval (CI) 1.48, 2.67] than children born full term (39 to <41 weeks). Early term births (37 to <39 weeks) had HR 1.01 (95% CI 0.84, 1.22), late term births (41 to <42 weeks) had HR 0.77 (95% 0.59, 1.01), and post-term births (≥42 weeks) had HR 0.56 (95% CI 0.32, 0.98). Large for gestational age was associated with lower risk of hospitalisation (HR 0.76, 95% CI 0.57, 0.99).

CONCLUSION

The association of preterm birth with childhood wheezing could be biologically mediated. We cannot rule out an association for early term births.

Reported associations between asthma and acute lymphoblastic leukemia: insights from a hybrid simulation study

Numerous studies have reported a protective association between asthma and acute lymphoblastic leukemia (ALL), but the causal structure of this association remains unclear. We present a hybrid simulation to examine the compatibility of this association with uncontrolled confounding by infection or another unmeasured factor. We generated a synthetic cohort using inputs on the interrelations of asthma, ALL, infections, and other suggested risk factors from the literature and the Danish National Birth Cohort. We computed odds ratios (ORs) between asthma and ALL in the synthetic cohort with and without adjustment for infections and other (including unmeasured) confounders. Only if infection was an extremely strong risk factor for asthma (OR of 10) and an extremely strong protective factor against ALL (OR of 0.1) was the asthma-ALL association compatible with the literature (OR of 0.78). Similarly, strong uncontrolled confounding by an unmeasured factor could downwardly bias the asthma-ALL association, but not enough to replicate findings in the literature. This investigation illustrates that the reported protective association between asthma and ALL is unlikely to be entirely due to uncontrolled confounding by infections or an unmeasured confounder alone. Simulation can be used to advance our understanding of risk factors for rare outcomes as demonstrated by this study.

Household Food Insecurity is Associated with Childhood Asthma

BACKGROUND

In 2013, 20% of U.S. households with children experienced food insecurity. Asthma afflicts over 7 million children; prevalence has steadily increased while incidence peaks in young children. Asthma and food insecurity share the determinants of poverty and race that are associated with weight, yet limited research on the relation between food insecurity and asthma exists.

OBJECTIVE

The objective of this study was to determine the association between food insecurity and asthma in a diverse sample of children.

METHODS

Cross-sectional data from grade 3 of the Early Childhood Longitudinal Study-Kindergarten Cohort were analyzed (n = 11,099). Food security based on the USDA module and asthma diagnosis were reported by parents; anthropometric factors were measured. Multivariate logistic regression models of food security and asthma were analyzed overall and by race/ethnicity.

RESULTS

Children in food-insecure households had a 4% higher adjusted odds of asthma (95% CI: 1.02, 1.06). Adjusted odds of asthma were also higher by 70% for males (95% CI: 1.69, 1.71), 53% for non-Hispanic black (NHB) children (95% CI: 1.51, 1.54), 20% for Hispanic children (95% CI: 1.19, 1.21), 38% for overweight children (95% CI: 1.36, 1.39), 67% for obese children (95% CI: 1.65, 1.68), 23% for low-birth weight children (95% CI: 1.21, 1.24), 24% if mothers had a high school diploma (95% CI: 1.23, 1.26), and 33% if mothers had some college education (95% CI: 1.32, 1.35). High-birth weight children (OR: 0.84; 95% CI: 0.83, 0.85) and those with foreign-born mothers (OR: 0.52; 95% CI: 0.51, 0.53) had lower odds of asthma. Being food-insecure remained positively associated with asthma in non-Hispanic whites and Hispanics but was inversely associated with odds among NHBs. Odds of asthma doubled (OR: 2.00; 95% CI: 1.97, 2.03) for all children in households that were both food-insecure and poor; this relation remained positive in race/ethnicity-specific models.

CONCLUSIONS

Food insecurity is positively associated with asthma in U.S. third graders, and household poverty strengthens the association.

Effects of birth weight and growth on childhood wheezing disorders: findings from the Born in Bradford Cohort

OBJECTIVES

To examine the effects of birth weight and childhood growth on childhood wheezing disorders. We hypothesised that low birth weight and fast growth during early age would increase the risk of wheezing disorders.

SETTING

Observational secondary analysis of data from the Born in Bradford cohort.

PARTICIPANTS

All children who were born at the Bradford Royal Infirmary hospital between March 2007 and December 2010 were eligible for the study. A total of 13,734 and 1598 children participated in the analyses of the effects of birth weight and growth on wheezing disorders, respectively.

PRIMARY AND SECONDARY OUTCOME MEASURES

Wheezing disorders diagnosis (diagnosed as asthma or had wheezing symptom) during the ages of 0-7 years were the primary outcome measures. Diagnosis of asthma and occurrence of wheezing during the same period were secondary outcome measures. Birth weight was classified as normal (2.5-4.0 kg), low (<2.5 kg) and high (>4.0 kg). Growth mixture models were used to drive growth pattern outcomes which were classified as 'normal', 'fast' and 'slow' growth based on their velocities between birth and 36 months.

RESULTS

The adjusted relative risks (RRs) of wheezing disorders diagnosis for the low and high birthweight children were 1.29 (95% CI 1.12 to 1.50; p=0.001) and 0.91 (95% CI 0.79 to 1.04; p=0.17), respectively. The adjusted RRs of wheezing disorders diagnosis were 1.30 (95% CI 0.56 to 3.06; p=0.54) and 0.60 (95% CI 0.16 to 2.18; p=0.44), respectively, for the 'fast' and 'slow' growth as compared with the 'normal' growth.

CONCLUSIONS

Low birth weight is associated with an increased risk of wheezing disorders; however, there is a weak evidence that suggests high birthweight children have a reduced risk in this birth cohort. Low birth weight coupled with a slower growth until 3 months and a sharp growth between 3 and 12 months has an increased risk of wheezing disorders diagnosis.