A novel study design to investigate the early-life origins of asthma in children (SAGE study)

Comparison and validation of algorithms for asthma diagnosis in an electronic medical record system

BACKGROUND

Asthma is one of the most common chronic health conditions, and to leverage the wealth of data in the electronic medical record (EMR), it is important to be able to accurately identify asthma diagnosis.

OBJECTIVE

We aimed to determine the rule-based algorithm with the most balanced performance for sensitivity and positive predictive value of asthma diagnosis.

METHODS

We performed a diagnostic accuracy study of multiple rule-based algorithms intended to identify asthma diagnosis in the EMR. Algorithm performance was validated by manual chart review of 795 charts of patients seen in a multisite, tertiary-level, pulmonary specialty clinic using explicit diagnostic criteria to distinguish asthma cases from controls.

RESULTS

An asthma diagnosis anywhere in the medical record had a 97% sensitivity and a 77% specificity for asthma (F-score 80) when tested on a validation set of asthma cases and nonasthma respiratory disease from a pulmonary specialty clinic. The most balanced performance was seen with asthma diagnosis restricted to an encounter, hospital problem, or problem list diagnosis with a sensitivity of 94% and specificity of 85% (F-score 84). High sensitivity was achieved with the modified Health Plan Employer Data and Information Set criteria and high specificity was achieved with the NUgene algorithm, an algorithm developed for identifying asthma cases by EMR for genome-wide association studies.

CONCLUSION

Asthma diagnosis can be accurately identified for research purposes by restricting to encounter, hospital problem, or problem list diagnosis in a pulmonary specialty clinic. Additional rules lead to steep drop-offs in algorithm sensitivity in our population.

Accuracy of Asthma Computable Phenotypes to Identify Pediatric Asthma at an Academic Institution

OBJECTIVES

Asthma is a heterogenous condition with significant diagnostic complexity, including variations in symptoms and temporal criteria. The disease can be difficult for clinicians to diagnose accurately. Properly identifying asthma patients from the electronic health record is consequently challenging as current algorithms (computable phenotypes) rely on diagnostic codes (e.g., International Classification of Disease, ICD) in addition to other criteria (e.g., inhaler medications)-but presume an accurate diagnosis. As such, there is no universally accepted or rigorously tested computable phenotype for asthma.

METHODS

We compared two established asthma computable phenotypes: the Chicago Area Patient-Outcomes Research Network (CAPriCORN) and Phenotype KnowledgeBase (PheKB). We established a large-scale, consensus gold standard (n = 1,365) from the University of California, Los Angeles Health System's clinical data warehouse for patients 5 to 17 years old. Results were manually reviewed and predictive performance (positive predictive value [PPV], sensitivity/specificity, F1-score) determined. We then examined the classification errors to gain insight for future algorithm optimizations.

RESULTS

As applied to our final cohort of 1,365 expert-defined gold standard patients, the CAPriCORN algorithms performed with a balanced PPV = 95.8% (95% CI: 94.4-97.2%), sensitivity = 85.7% (95% CI: 83.9-87.5%), and harmonized F1 = 90.4% (95% CI: 89.2-91.7%). The PheKB algorithm was performed with a balanced PPV = 83.1% (95% CI: 80.5-85.7%), sensitivity = 69.4% (95% CI: 66.3-72.5%), and F1 = 75.4% (95% CI: 73.1-77.8%). Four categories of errors were identified related to method limitations, disease definition, human error, and design implementation.

CONCLUSION

The performance of the CAPriCORN and PheKB algorithms was lower than previously reported as applied to pediatric data (PPV = 97.7 and 96%, respectively). There is room to improve the performance of current methods, including targeted use of natural language processing and clinical feature engineering.

A systematic review of asthma case definitions in 67 birth cohort studies

BACKGROUND

Birth cohort studies are a valuable source of information about potential risk factors for childhood asthma. To better understand similarities and variations in findings between birth cohort studies, the methodologies used to measure asthma require consideration.

OBJECTIVE

To review and appraise the definitions of "asthma" used in birth cohort studies.

METHODS

A literature search, conducted in December 2017 in the MEDLINE database and birth cohort repositories, identified 1721 citations published since 1990. Information extracted included: study name, year of publication, sample size, sample age, prevalence of asthma (%), study region, source of information about asthma, measured outcome, and asthma case definition. A meta-analysis evaluated whether asthma prevalence in cohorts from Europe and North America varied by the studies' definition of asthma and by their data sources.

RESULTS

The final review included 67 birth cohorts, of which 48 (72%) were from Europe, 14 (21%) from North America, 3 (5%) from Oceania, 1 (1%) from Asia and 1 (1%) from South America. We identified three measured outcomes: "asthma ever", "current asthma", and "asthma" without further specification. Definitions of "asthma ever" were primarily based upon an affirmative parental response to the question whether the child had ever been diagnosed with asthma by a physician. The most frequently used definition of "current asthma" was "asthma ever" and either asthma symptoms or asthma medications in the last 12 months. This definition of "current asthma" was used in 16 cohorts. There was no statistically significant difference in the pooled asthma prevalence in European and North American cohorts that used questionnaire alone versus other data sources to classify asthma.

CONCLUSION

There is substantial heterogeneity in childhood asthma definitions in birth cohort studies. Standardisation of asthma case definitions will improve the comparability and utility of future cohort studies and enable meta-analyses.

The validity of diagnostic algorithms to identify asthma patients in healthcare administrative databases: a systematic literature review

OBJECTIVES

To review the available evidence supporting the validity of algorithms to identify asthma patients in healthcare administrative databases.

METHODS

A systematic literature search was conducted on multiple databases from inception to March 2020 to identify studies that reported the validity of case-finding asthma algorithms applied to healthcare administrative data. Following an initial screening of abstracts, two investigators independently assessed the full text of studies which met the pre-determined eligibility criteria. Data on study population and algorithm characteristics were extracted. A revised version of the Quality Assessment of Diagnostic Accuracy Studies tool was used to evaluate the risk of bias and generalizability of studies.

RESULTS

A total of 20 studies met the eligibility criteria. Algorithms which incorporated ≥1 diagnostic code for asthma over a 1-year period appeared to be valid in both adult and pediatric populations (sensitivity ≥ 85%; specificity ≥ 89%; PPV ≥ 70%). The validity was enhanced when: (1) the time frame to capture asthma cases was increased to two years; (2) ≥2 asthma diagnostic codes were considered; and (3) when diagnoses were recorded by a pulmonologist. Algorithms which integrated pharmacy claims data appeared to correctly identify asthma patients; however, the extent to which asthma medications can improve the validity remains unclear. The quality of several studies was high, although disease progression bias and biases related to self-reported data was observed in some studies.

CONCLUSIONS

Healthcare administrative databases are adequate sources to identify asthma patients. More restrictive definitions based on both asthma diagnoses and asthma medications may enhance validity, although further research is required to confirm this hypothesis.

Calcium Intake in Children with Eczema and/or Food Allergy: A Prospective Cohort Study

Eczema and food allergy may impact diet. Using data from a cohort of Manitoba children born in 1995, we examined calcium intake, defined as the frequency and quality of calcium products consumed (with the exception of cheese), amongst Manitoba adolescents (12-14 years) with eczema or food allergy in childhood (7-8 years) or adolescence. At both ages, children were assessed by a physician for eczema and food allergy. Adolescents completed food frequency questionnaires. Calcium intake was defined as 1+ vs. <1 weekly. Linear and logistic regression was used as appropriate, with adjustments for confounders. Overall, 468 adolescents were included, of whom 62 (13.3%) had eczema only in childhood, 25 (5.3%) had food allergy only, and 26 (5.6%) had eczema and food allergy. Compared to children without eczema, those with eczema only had poorer calcium intake in adolescence (β -0.44; 95%CI -0.96; 0.00). Girls, but not boys, with eczema in childhood had poorer calcium intake in adolescence than girls without eczema (β -0.84; 95%CI -1.60; -0.08). These patterns persisted even if children experienced transient vs. persistent eczema to adolescence. Similar but non-significant trends were found for food allergy. Childhood eczema is associated with significantly lower calcium intake and consumption in adolescence. These differences persist to adolescence, even if a child "outgrows" their allergic condition.

Maternal food allergy is associated with daughters' menarche in early adolescence

Rationale

Associations between allergic disease and puberty amongst females have been widely studied. However, this association has received less attention in multigenerational populations. To this end, we sought to examine maternal allergic disease status ever, and daughters’ menarche.

Methods

In a cohort of children born in 1995, in Manitoba, Canada, we considered maternal allergic disease ever to daughters’ age 7–8 years, and daughters’ menarche at ages 12–14 years. We included all participants for whom we had information on both the exposure and the outcome of those eligible. Data were analysed using descriptive statistics and logistic regression, with adjustment for confounding variables.

Results

Overall, the prevalences of maternal allergic diseases were 28.6% for asthma 18.8% for food allergy, 27.3% for eczema and 45.5% for rhinitis. By age 12–14 years, 41.6% (64/159) girls had reached menarche. Maternal food allergy was significantly associated with daughters’ menarche (OR 4.39, 95% CI 1.51–12.73), whereas no association was found for maternal asthma, eczema or rhinitis. With consideration to comorbid disease, a combination of maternal asthma + food allergy was associated with daughters’ menarche by age 12–14 years (OR 6.41; 95% CI 1.32–31.01).

Conclusions

Maternal food allergy ever is associated with daughters’ menarche by age 12–14 years.

Association between early-childhood antibiotic exposure and subsequent asthma in the US Medicaid population

BACKGROUND

Although socioeconomically disadvantaged children have an increased risk of asthma, the association between early-childhood antibiotics and the incidence of asthma among such children has had limited study.

OBJECTIVE

To examine the association between antibiotic fills in the first 2 years of life and risk of developing asthma among children enrolled in Medicaid plans.

METHODS

This retrospective cohort study of children with continuous medical and pharmacy coverage from birth to 2.5 years of age was performed from July 1, 2012, to November 31, 2018. We excluded children with a diagnosis of asthma before 2.5 years of age. Hazard ratios (HRs) and 95% CIs were estimated from Cox proportional hazards regression models. Covariates included sex, preterm birth, cesarean delivery, and mother's asthma status.

RESULTS

There were 79,582 children in the study cohort of whom 29,931 (37.6%) had 0 antibiotic prescriptions filled, 27,403 (34.4%) had 1 or 2 prescriptions filled, and 22,248 (28.0%) had 3 or more prescriptions filled. A total of 2381 new cases of asthma were observed in 89,545 person-years of follow-up. After adjustment, receipt of 1 or 2 antibiotics was associated with an increased risk of developing asthma, relative to 0 antibiotics (HR, 1.34; 95% CI, 1.21-1.49), and receipt of 3 or more antibiotics was associated with greater increased risk relative to 0 antibiotics (HR, 1.71; 95% CI, 1.54-1.90). After adjustment, the absolute risk of developing asthma by age 4.0 years increased from 2.7% (0 antibiotics) to 3.6% (1-2 antibiotics) and 4.5% (≥3 antibiotics).

CONCLUSION

Antibiotic prescriptions filled in the first 2 years of life were associated with an increased risk of asthma diagnosis from 2.5 to 5 years of age in a Medicaid population.

Early-life origins of disparities in chronic diseases among Indigenous youth: pathways to recovering health disparities from intergenerational trauma

Indigenous women and children experience some of the most profound health disparities globally. These disparities are grounded in historical and contemporary trauma secondary to colonial atrocities perpetuated by settler society. The health disparities that exist for chronic diseases may have their origins in early-life exposures that Indigenous women and children face. Mechanistically, there is evidence that these adverse exposures epigenetically modify genes associated with cardiometabolic disease risk. Interventions designed to support a resilient pregnancy and first 1000 days of life should abrogate disparities in early-life socioeconomic status. Breastfeeding, prenatal care and early child education are key targets for governments and health care providers to start addressing current health disparities in cardiometabolic diseases among Indigenous youth. Programmes grounded in cultural safety and co-developed with communities have successfully reduced health disparities. More works of this kind are needed to reduce inequities in cardiometabolic diseases among Indigenous women and children worldwide.

Validation of asthma recording in electronic health records: a systematic review

Objective

To describe the methods used to validate asthma diagnoses in electronic health records and summarize the results of the validation studies.

Background

Electronic health records are increasingly being used for research on asthma to inform health services and health policy. Validation of the recording of asthma diagnoses in electronic health records is essential to use these databases for credible epidemiological asthma research.

Methods

We searched EMBASE and MEDLINE databases for studies that validated asthma diagnoses detected in electronic health records up to October 2016. Two reviewers independently assessed the full text against the predetermined inclusion criteria. Key data including author, year, data source, case definitions, reference standard, and validation statistics (including sensitivity, specificity, positive predictive value [PPV], and negative predictive value [NPV]) were summarized in two tables.

Results

Thirteen studies met the inclusion criteria. Most studies demonstrated a high validity using at least one case definition (PPV >80%). Ten studies used a manual validation as the reference standard; each had at least one case definition with a PPV of at least 63%, up to 100%. We also found two studies using a second independent database to validate asthma diagnoses. The PPVs of the best performing case definitions ranged from 46% to 58%. We found one study which used a questionnaire as the reference standard to validate a database case definition; the PPV of the case definition algorithm in this study was 89%.

Conclusion

Attaining high PPVs (>80%) is possible using each of the discussed validation methods. Identifying asthma cases in electronic health records is possible with high sensitivity, specificity or PPV, by combining multiple data sources, or by focusing on specific test measures. Studies testing a range of case definitions show wide variation in the validity of each definition, suggesting this may be important for obtaining asthma definitions with optimal validity.

Validation of asthma recording in the Clinical Practice Research Datalink (CPRD)

OBJECTIVES

The optimal method of identifying people with asthma from electronic health records in primary care is not known. The aim of this study is to determine the positive predictive value (PPV) of different algorithms using clinical codes and prescription data to identify people with asthma in the United Kingdom Clinical Practice Research Datalink (CPRD).

METHODS

684 participants registered with a general practitioner (GP) practice contributing to CPRD between 1 December 2013 and 30 November 2015 were selected according to one of eight predefined potential asthma identification algorithms. A questionnaire was sent to the GPs to confirm asthma status and provide additional information to support an asthma diagnosis. Two study physicians independently reviewed and adjudicated the questionnaires and additional information to form a gold standard for asthma diagnosis. The PPV was calculated for each algorithm.

RESULTS

684 questionnaires were sent, of which 494 (72%) were returned and 475 (69%) were complete and analysed. All five algorithms including a specific Read code indicating asthma or non-specific Read code accompanied by additional conditions performed well. The PPV for asthma diagnosis using only a specific asthma code was 86.4% (95% CI 77.4% to 95.4%). Extra information on asthma medication prescription (PPV 83.3%), evidence of reversibility testing (PPV 86.0%) or a combination of all three selection criteria (PPV 86.4%) did not result in a higher PPV. The algorithm using non-specific asthma codes, information on reversibility testing and respiratory medication use scored highest (PPV 90.7%, 95% CI (82.8% to 98.7%), but had a much lower identifiable population. Algorithms based on asthma symptom codes had low PPVs (43.1% to 57.8%)%).

CONCLUSIONS

People with asthma can be accurately identified from UK primary care records using specific Read codes. The inclusion of spirometry or asthma medications in the algorithm did not clearly improve accuracy.

ETHICS AND DISSEMINATION

The protocol for this research was approved by the Independent Scientific Advisory Committee (ISAC) for MHRA Database Research (protocol number15_257) and the approved protocol was made available to the journal and reviewers during peer review. Generic ethical approval for observational research using the CPRD with approval from ISAC has been granted by a Health Research Authority Research Ethics Committee (East Midlands-Derby, REC reference number 05/MRE04/87).The results will be submitted for publication and will be disseminated through research conferences and peer-reviewed journals.

Genome-Wide Interaction Analysis of Air Pollution Exposure and Childhood Asthma with Functional Follow-up

RATIONALE

The evidence supporting an association between traffic-related air pollution exposure and incident childhood asthma is inconsistent and may depend on genetic factors.

OBJECTIVES

To identify gene-environment interaction effects on childhood asthma using genome-wide single-nucleotide polymorphism (SNP) data and air pollution exposure. Identified loci were further analyzed at epigenetic and transcriptomic levels.

METHODS

We used land use regression models to estimate individual air pollution exposure (represented by outdoor NO₂ levels) at the birth address and performed a genome-wide interaction study for doctors' diagnoses of asthma up to 8 years in three European birth cohorts (n = 1,534) with look-up for interaction in two separate North American cohorts, CHS (Children's Health Study) and CAPPS/SAGE (Canadian Asthma Primary Prevention Study/Study of Asthma, Genetics and Environment) (n = 1,602 and 186 subjects, respectively). We assessed expression quantitative trait locus effects in human lung specimens and blood, as well as associations among air pollution exposure, methylation, and transcriptomic patterns.

MEASUREMENTS AND MAIN RESULTS

In the European cohorts, 186 SNPs had an interaction P < 1 × 10^-4 and a look-up evaluation of these disclosed 8 SNPs in 4 loci, with an interaction P < 0.05 in the large CHS study, but not in CAPPS/SAGE. Three SNPs within adenylate cyclase 2 (ADCY2) showed the same direction of the interaction effect and were found to influence ADCY2 gene expression in peripheral blood (P = 4.50 × 10^-4). One other SNP with P < 0.05 for interaction in CHS, rs686237, strongly influenced UDP-Gal:betaGlcNAc β-1,4-galactosyltransferase, polypeptide 5 (B4GALT5) expression in lung tissue (P = 1.18 × 10^-17). Air pollution exposure was associated with differential discs, large homolog 2 (DLG2) methylation and expression.

CONCLUSIONS

Our results indicated that gene-environment interactions are important for asthma development and provided supportive evidence for interaction with air pollution for ADCY2, B4GALT5, and DLG2.

Residential greenness is differentially associated with childhood allergic rhinitis and aeroallergen sensitization in seven birth cohorts

BACKGROUND

The prevalence of allergic rhinitis is high, but the role of environmental factors remains unclear. We examined cohort-specific and combined associations of residential greenness with allergic rhinitis and aeroallergen sensitization based on individual data from Swedish (BAMSE), Australian (MACS), Dutch (PIAMA), Canadian (CAPPS and SAGE), and German (GINIplus and LISAplus) birth cohorts (n = 13 016).

METHODS

Allergic rhinitis (doctor diagnosis/symptoms) and aeroallergen sensitization were assessed in children aged 6-8 years in six cohorts and 10-12 years in five cohorts. Residential greenness was defined as the mean Normalized Difference Vegetation Index (NDVI) in a 500-m buffer around the home address at the time of health assessment. Cohort-specific associations per 0.2 unit increase in NDVI were assessed using logistic regression models and combined in a random-effects meta-analysis.

RESULTS

Greenness in a 500-m buffer was positively associated with allergic rhinitis at 6-8 years in BAMSE (odds ratio = 1.42, 95% confidence interval [1.13, 1.79]) and GINI/LISA South (1.69 [1.19, 2.41]) but inversely associated in GINI/LISA North (0.61 [0.36, 1.01]) and PIAMA (0.67 [0.47, 0.95]). Effect estimates in CAPPS and SAGE were also conflicting but not significant (0.63 [0.32, 1.24] and 1.31 [0.81, 2.12], respectively). All meta-analyses were nonsignificant. Results were similar for aeroallergen sensitization at 6-8 years and both outcomes at 10-12 years. Stratification by NO2 concentrations, population density, an urban vs rural marker, and moving did not reveal consistent trends within subgroups.

CONCLUSION

Although residential greenness appears to be associated with childhood allergic rhinitis and aeroallergen sensitization, the effect direction varies by location.

Children's Health and Indoor Air Quality in Primary Schools and Homes in Portugal-Study Design

The main aim of the research project "On the Contribution of Schools to Children's Overall Indoor Air Exposure" is to study associations between adverse health effects, namely, allergy, asthma, and respiratory symptoms, and indoor air pollutants to which children are exposed to in primary schools and homes. Specifically, this investigation reports on the design of the study and methods used for data collection within the research project and discusses factors that need to be considered when designing such a study. Further, preliminary findings concerning descriptors of selected characteristics in schools and homes, the study population, and clinical examination are presented. The research project was designed in two phases. In the first phase, 20 public primary schools were selected and a detailed inspection and indoor air quality (IAQ) measurements including volatile organic compounds (VOC), aldehydes, particulate matter (PM2.5, PM10), carbon dioxide (CO2), carbon monoxide (CO), bacteria, fungi, temperature, and relative humidity were conducted. A questionnaire survey of 1600 children of ages 8-9 years was undertaken and a lung function test, exhaled nitric oxide (eNO), and tear film stability testing were performed. The questionnaire focused on children's health and on the environment in their school and homes. One thousand and ninety-nine questionnaires were returned. In the second phase, a subsample of 68 children was enrolled for further studies, including a walk-through inspection and checklist and an extensive set of IAQ measurements in their homes. The acquired data are relevant to assess children's environmental exposures and health status.

Maternal distress in early life predicts the waist-to-hip ratio in schoolchildren

We report on life course stress determinants of overweight in children, using data from the longitudinal follow-up of the nested case-control arm of the SAGE (study of asthma genes and the environment) birth cohort in Manitoba, Canada. Waist and hip measurements were obtained during a clinic visit at age 9-11 years. Multiple linear regression was conducted to determine the relationship between the waist-to-hip ratio and maternal smoking during pregnancy, postpartum maternal distress and stress reactivity in children (cortisol, cortisol-DHEA [dihydroepiandrostrenone] ratio quartiles) following a clinic stressor at age 8-10 years. We found waist-to-hip risk at age 9-11 years to be elevated among boys and girls whose mothers had experienced distress in the postnatal period. This association varied by gender and asthma status. In healthy girls, postpartum distress increased waist-to-hip ratio by a factor of 0.034 (P < 0.01), independent of the child's stage of puberty and adrenarche, cortisol-DHEA ratio and duration of exclusive breastfeeding. Among girls with asthma, maternal smoking during pregnancy was associated with an increased waist-to-hip ratio, if the mother also experienced distress in the postpartum period (0.072, P = 0.038). Among asthmatic boys, an association between maternal distress and waist-to-hip ratio was evident at the highest cortisol-DHEA ratios. Stress-induced changes to leptin and infant over-eating pathways were proposed to explain the postnatal maternal distress effects. Drawing on the theories of evolutionary biology, our findings underscore the significance of postnatal stress in disrupting hypothalamic-pituitary-adrenal axis function in infants and increasing risk for child overweight.

Infant antibiotic exposure and the development of childhood overweight and central adiposity

BACKGROUND

Obesity has been associated with disruption of the gut microbiota, which is established during infancy and vulnerable to disruption by antibiotics.

OBJECTIVES

To investigate the association between early-life antibiotic exposure and subsequent development of overweight and central adiposity.

METHODS

Provincial health-care records were linked to clinical and survey data from a Canadian longitudinal birth cohort study. Antibiotic exposure during the first year of life was documented from prescription records. Overweight and central adiposity were determined from anthropometric measurements at ages 9 (n=616) and 12 (n=431). Associations were determined by multiple logistic regression.

RESULTS

Infants receiving antibiotics in the first year of life were more likely to be overweight later in childhood compared with those who were unexposed (32.4 versus 18.2% at age 12, P=0.002). Following adjustment for birth weight, breastfeeding, maternal overweight and other potential confounders, this association persisted in boys (aOR 5.35, 95% confidence interval (CI) 1.94-14.72) but not in girls (aOR 1.13, CI 0.46-2.81). Similar gender-specific associations were found for overweight at age 9 (aOR 2.19, CI 1.06-4.54 for boys; aOR 1.20, CI 0.53-2.70 for girls) and for high central adiposity at age 12 (aOR 2.85, CI 1.24-6.51 for boys; aOR 1.59, CI 0.68-3.68 for girls).

CONCLUSIONS

Among boys, antibiotic exposure during the first year of life was associated with an increased risk of overweight and central adiposity in preadolescence, indicating that antibiotic stewardship is particularly important during infancy. Given the current epidemic of childhood obesity and the high prevalence of infant antibiotic exposure, further studies are necessary to determine the mechanisms underlying this association, to identify the long-term health consequences, and to develop strategies for mitigating these effects when antibiotic exposure cannot be avoided.

Exposure to Beta-(1,3)-D-glucan in house dust at age 7-10 is associated with airway hyperresponsiveness and atopic asthma by age 11-14

BACKGROUND

Mould exposure has been linked to childhood asthma and bronchial hyper-responsiveness. Few studies have assessed beta-(1,3)-d-glucan (beta-glucan), a significant fungal cell wall constituent, in relation to asthma in adolescence.

OBJECTIVE

To determine whether house dust-derived beta-glucan exposure at age 7-10 is associated with the development and persistence of atopic and non-atopic asthma, and bronchial hyper-responsiveness (BHR) by age 11-14.

METHODS

Dust samples were collected from the 1995 Study of Asthma, Genes, and Environment (SAGE) birth cohort. This cohort was derived from Manitoba provincial healthcare administrative records of children high and low risk for asthma. Samples were collected from the homes of 422 children at age 7-10 and analyzed using beta-glucan and endotoxin-specific Limulus Amoebocyte Lysate assays. Asthma, atopy, and BHR status of each child were also assessed at ages 7-10 and 11-14.

RESULTS

At age 7-10, beta-glucan dust levels in the home were associated with persistent atopic asthma at age 11-14 (OR 1.79 for each unit increase in levels, 95% CI 1.14-2.81), independent of endotoxin exposure, and Alternaria or Cladosporium sensitization. The likelihood of BHR almost doubled with unit increases in dust beta-glucan in asthmatic children. In children without asthma, exposure to high beta-glucan levels at age 7-10 also elevated risk for BHR in adolescence (OR 1.74, 95% CI 1.05-2.89). New-onset atopic asthma was twice more likely following high beta-glucan exposure in children without asthma but the association did not reach statistical significance. No associations were evident with concurrent asthma phenotype at age 7-10 or non-atopic asthma at age 11-14.

CONCLUSION

These findings implicate home beta-glucan exposure at school-age as a risk factor for persistent atopic asthma and new-onset BHR. The higher prevalence of BHR in urban adolescents may be propagated by this home exposure.

GSTP1 and TNF Gene variants and associations between air pollution and incident childhood asthma: the traffic, asthma and genetics (TAG) study

BACKGROUND

Genetics may partially explain observed heterogeneity in associations between traffic-related air pollution and incident asthma.

OBJECTIVE

Our aim was to investigate the impact of gene variants associated with oxidative stress and inflammation on associations between air pollution and incident childhood asthma.

METHODS

Traffic-related air pollution, asthma, wheeze, gene variant, and potential confounder data were pooled across six birth cohorts. Parents reported physician-diagnosed asthma and wheeze from birth to 7-8 years of age (confirmed by pediatric allergist in two cohorts). Individual estimates of annual average air pollution [nitrogen dioxide (NO2), particulate matter ≤ 2.5 μm (PM2.5), PM2.5 absorbance, ozone] were assigned to each child's birth address using land use regression, atmospheric modeling, and ambient monitoring data. Effect modification by variants in GSTP1 (rs1138272/Ala114Val and rs1695/IIe105Val) and TNF (rs1800629/G-308A) was investigated.

RESULTS

Data on asthma, wheeze, potential confounders, at least one SNP of interest, and NO2 were available for 5,115 children. GSTP1 rs1138272 and TNF rs1800629 SNPs were associated with asthma and wheeze, respectively. In relation to air pollution exposure, children with one or more GSTP1 rs1138272 minor allele were at increased risk of current asthma [odds ratio (OR) = 2.59; 95% CI: 1.43, 4.68 per 10 μg/m3 NO2] and ever asthma (OR = 1.64; 95% CI: 1.06, 2.53) compared with homozygous major allele carriers (OR = 0.95; 95% CI: 0.68, 1.32 for current and OR = 1.20; 95% CI: 0.98, 1.48 for ever asthma; Bonferroni-corrected interaction p = 0.04 and 0.01, respectively). Similarly, for GSTP1 rs1695, associations between NO2 and current and ever asthma had ORs of 1.43 (95% CI: 1.03, 1.98) and 1.36 (95% CI: 1.08, 1.70), respectively, for minor allele carriers compared with ORs of 0.82 (95% CI: 0.52, 1.32) and 1.12 (95% CI: 0.84, 1.49) for homozygous major allele carriers (Bonferroni-corrected interaction p-values 0.48 and 0.09). There were no clear differences by TNF genotype.

CONCLUSIONS

Children carrying GSTP1 rs1138272 or rs1695 minor alleles may constitute a susceptible population at increased risk of asthma associated with air pollution.

Traffic, asthma and genetics: combining international birth cohort data to examine genetics as a mediator of traffic-related air pollution's impact on childhood asthma

Associations between traffic-related air pollution and incident childhood asthma can be strengthened by analysis of gene-environment interactions, but studies have typically been limited by lack of study power. We combined data from six birth cohorts on: asthma, eczema and allergic rhinitis to 7/8 years, and candidate genes. Individual-level assessment of traffic-related air pollution exposure was estimated using land use regression or dispersion modeling. A total of 11,760 children were included in the Traffic, Asthma and Genetics (TAG) Study; 6.3 % reported physician-diagnosed asthma at school-age, 16.0 % had asthma at anytime during childhood, 14.1 % had allergic rhinitis at school-age, 10.0 % had eczema at school-age and 33.1 % were sensitized to any allergen. For GSTP1 rs1138272, the prevalence of heterozygosity was 16 % (range amongst individual cohorts, 11-17 %) and homozygosity for the minor allele was 1 % (0-2 %). For GSTP1 rs1695, the prevalence of heterozygosity was 45 % (40-48 %) and homozygosity for the minor allele, 12 % (10-12 %). For TNF rs1800629, the prevalence of heterozygosity was 29 % (25-32 %) and homozygosity for the minor allele, 3 % (1-3 %). TAG comprises a rich database, the largest of its kind, for investigating the effect of genotype on the association between air pollution and childhood allergic disease.

Association of maternal diabetes and child asthma

BACKGROUND

Perinatal programming is an emerging theory for the fetal origins of chronic disease. Maternal asthma and environmental tobacco smoke (ETS) are two of the best-known triggers for the perinatal programming of asthma, while the potential role of maternal diabetes has not been widely studied.

OBJECTIVE

To determine if maternal diabetes is associated with child asthma, and if so, whether it modifies the effects of ETS exposure and maternal asthma.

METHODS

We studied 3,574 Canadian children, aged 7-8 years, enrolled in a population-based birth cohort. Standardized questionnaires were completed by the children's parents, and data were analyzed by multivariable logistic regression.

RESULTS

Asthma was reported in 442 children (12.4%). Compared to those without asthma, asthmatic children were more likely to have mothers (P = 0.003), but not fathers (P = 0.89), with diabetes. Among children without maternal history of diabetes, the likelihood of child asthma was 1.4-fold higher in those exposed to ETS (adjusted odds ratio, 1.40; 95% confidence interval, 1.13-1.73), and 3.6-fold higher in those with maternal asthma (3.59; 2.71-4.76). Among children born to diabetic mothers, these risks were amplified to 5.7-fold (5.68; 1.18-27.37) and 11.3-fold (11.30; 2.26-56.38), respectively. In the absence of maternal asthma or ETS, maternal diabetes was not associated with child asthma (0.65, 0.16-2.56).

CONCLUSION

Our findings suggest that maternal diabetes may contribute to the perinatal programming of child asthma by amplifying the detrimental effects of ETS exposure and maternal asthma.

Childhood allergic rhinitis, traffic-related air pollution, and variability in the GSTP1, TNF, TLR2, and TLR4 genes: results from the TAG Study

BACKGROUND

Associations between traffic-related air pollution (TRAP) and allergic rhinitis remain inconsistent, possibly because of unexplored gene-environment interactions.

OBJECTIVE

In a pooled analysis of 6 birth cohorts (Ntotal = 15,299), we examined whether TRAP and genetic polymorphisms related to inflammation and oxidative stress predict allergic rhinitis and sensitization.

METHODS

Allergic rhinitis was defined with a doctor diagnosis or reported symptoms at age 7 or 8 years. Associations between nitrogen dioxide, particulate matter 2.5 (PM2.5) mass, PM2.5 absorbance, and ozone, estimated for each child at the year of birth, and single nucleotide polymorphisms within the GSTP1, TNF, TLR2, or TLR4 genes with allergic rhinitis and aeroallergen sensitization were examined with logistic regression. Models were stratified by genotype and interaction terms tested for gene-environment associations.

RESULTS

Point estimates for associations between nitrogen dioxide, PM2.5 mass, and PM2.5 absorbance with allergic rhinitis were elevated, but only that for PM2.5 mass was statistically significant (1.37 [1.01, 1.86] per 5 μg/m(3)). This result was not robust to single-cohort exclusions. Carriers of at least 1 minor rs1800629 (TNF) or rs1927911 (TLR4) allele were consistently at an increased risk of developing allergic rhinitis (1.19 [1.00, 1.41] and 1.24 [1.01, 1.53], respectively), regardless of TRAP exposure. No evidence of gene-environment interactions was observed.

CONCLUSION

The generally null effect of TRAP on allergic rhinitis and aeroallergen sensitization was not modified by the studied variants in the GSTP1, TNF, TLR2, or TLR4 genes. Children carrying a minor rs1800629 (TNF) or rs1927911 (TLR4) allele may be at a higher risk of allergic rhinitis.

Low vegetable intake is associated with allergic asthma and moderate-to-severe airway hyperresponsiveness

BACKGROUND

In recent decades, children's diet quality has changed and asthma prevalence has increased, although it remains unclear if these events are associated.

OBJECTIVE

To examine children's total and component diet quality and asthma and airway hyperresponsiveness (AHR), a proxy for asthma severity.

METHODS

Food frequency questionnaires adapted from the Nurses' Health Study and supplemented with foods whose nutrients which have garnered interest of late in relation to asthma were administered. From these data, diet quality scores (total and component), based on the Youth Healthy Eating Index (YHEI adapted) were developed. Asthma assessments were performed by pediatric allergists and classified by atopic status: Allergic asthma (≥1 positive skin prick test to common allergens >3 mm compared to negative control) versus non-allergic asthma (negative skin prick test). AHR was assessed via the Cockcroft technique. Participants included 270 boys (30% with asthma) and 206 girls (33% with asthma) involved in the 1995 Manitoba Prospective Cohort Study nested case-control study. Logistic regression was used to examine associations between diet quality and asthma, and multinomial logistic regression was used to examine associations between diet quality and AHR.

RESULTS

Four hundred seventy six children (56.7% boys) were seen at 12.6 ± 0.5 years. Asthma and AHR prevalence were 26.2 and 53.8%, respectively. In fully adjusted models, high vegetable intake was protective against allergic asthma (OR 0.49; 95% CI 0.29-0.84; P < 0.009) and moderate/severe AHR (OR 0.58; 0.37-0.91; P < 0.019).

CONCLUSIONS

Vegetable intake is inversely associated with allergic asthma and moderate/severe AHR.

Children's health and its association with indoor environments in Danish homes and daycare centres - methods

The principle objective of the Danish research program 'Indoor Environment and Children's Health' (IECH) was to explore associations between various exposures that children experience in their indoor environments (specifically their homes and daycare centers) and their well-being and health. The targeted health endpoints were allergy, asthma, and certain respiratory symptoms. The study was designed with two stages. In the first stage, a questionnaire survey was distributed to more than 17,000 families with children between the ages of 1 and 5. The questionnaire focused on the children's health and the environments within the homes they inhabited and daycare facilities they attended. More than 11,000 questionnaires were returned. In the second stage, a subsample of 500 children was selected for more detailed studies, including an extensive set of measurements in their homes and daycare centers and a clinical examination; all clinical examinations were carried out by the same physician. In this study, the methods used for data collection within the IECH research program are presented and discussed. Furthermore, initial findings are presented regarding descriptors of the study population and selected characteristics of the children's dwellings and daycare centers.

PRACTICAL IMPLICATIONS

This study outlines methods that might be followed by future investigators conducting large-scale field studies of potential connections between various indoor environmental factors and selected health endpoints. Of particular note are (i) the two-stage design - a broad questionnaire-based survey followed by a more intensive set of measurements among a subset of participants who have been selected based on their responses to the questionnaire; (ii) the case-base approach utilized in the stage 2 in contrast to the more commonly used case-control approach; (iii) the inclusion of the children's daycare environment when conducting intensive sampling to more fully capture the children's total indoor exposure; and (iv) all clinical examinations conducted by the same physician. We recognize that future investigators are unlikely to fully duplicate the methods outlined in this study, but we hope that it provides a useful starting point in terms of factors that might be considered when designing such a study.

A meta-analysis of genome-wide association studies for serum total IgE in diverse study populations

BACKGROUND

IgE is both a marker and mediator of allergic inflammation. Despite reported differences in serum total IgE levels by race-ethnicity, African American and Latino subjects have not been well represented in genetic studies of total IgE.

OBJECTIVE

We sought to identify the genetic predictors of serum total IgE levels.

METHODS

We used genome-wide association data from 4292 subjects (2469 African Americans, 1564 European Americans, and 259 Latinos) in the EVE Asthma Genetics Consortium. Tests for association were performed within each cohort by race-ethnic group (ie, African American, Latino, and European American) and asthma status. The resulting P values were meta-analyzed, accounting for sample size and direction of effect. Top single nucleotide polymorphism associations from the meta-analysis were reassessed in 6 additional cohorts comprising 5767 subjects.

RESULTS

We identified 10 unique regions in which the combined association statistic was associated with total serum IgE levels (P<5.0×10(-6)) and the minor allele frequency was 5% or greater in 2 or more population groups. Variant rs9469220, corresponding to HLA-DQB1, was the single nucleotide polymorphism most significantly associated with serum total IgE levels when assessed in both the replication cohorts and the discovery and replication sets combined (P=.007 and 2.45×10(-7), respectively). In addition, findings from earlier genome-wide association studies were also validated in the current meta-analysis.

CONCLUSION

This meta-analysis independently identified a variant near HLA-DQB1 as a predictor of total serum IgE levels in multiple race-ethnic groups. This study also extends and confirms the findings of earlier genome-wide association analyses in African American and Latino subjects.

An inventory of Canadian pregnancy and birth cohort studies: research in progress

Background

A web-based inventory was developed as a voluntary registry of Canadian pregnancy and birth cohort studies, with the objective to foster collaboration and sharing of research tools among cohort study groups as a means to enrich research in maternal and child health across Canada.

Description

Information on existing birth cohort studies conducted in Canada exclusively or as part of broader international initiatives was accessed by searching the literature in PubMed and PsychInfo databases. Additional studies were identified by enquiring about the research activities of researchers at Canadian universities or working in affiliated hospitals or research centres or institutes. Of the fifty-eight birth cohort studies initially identified, forty-six were incorporated into the inventory if they were of a retrospective and/or prospective longitudinal design and with a minimum of two phases of data collection, with the first period having occurred before, during, or shortly after pregnancy and had an initial study sample size of a minimum of 200 participants.

Information collected from each study was organized into four main categories: basic information, data source and period of collection, exposures, and outcome measures and was coded and entered into an Excel spreadsheet. The information incorporated into the Excel spreadsheet was double checked, completed when necessary, and verified for completeness and accuracy by contacting the principal investigator or research coordinator. All data collected were then uploaded onto the website of the Institute of Human Development Child and Youth Health of the Canadian Institutes of Health Research. Subsequently, the database was updated and developed as an online searchable inventory on the website of the Maternal, Infant, Child and Youth Research Network.

Conclusions

This inventory is unique, as it represents detailed information assembled for the first time on a large number of Canadian birth cohort studies. Such information provides a valuable resource for investigators in the planning stages of cohort studies and identifying current research gaps.

Associations and interactions of genetic polymorphisms in innate immunity genes with early viral infections and susceptibility to asthma and asthma-related phenotypes

BACKGROUND

The innate immune system is essential for host survival because of its ability to recognize invading pathogens and mount defensive responses.

OBJECTIVES

We sought to identify genetic associations of innate immunity genes with atopy and asthma and interactions with early viral infections (first 12 months of life) in a high-risk birth cohort.

METHODS

Three Canadian family-based studies and 1 Australian population-based case-control study (n = 5565) were used to investigate associations of 321 single nucleotide polymorphisms (SNPs) in 26 innate immunity genes with atopy, asthma, atopic asthma, and airway hyperresponsiveness. Interactions between innate immunity genes and early viral exposure to 3 common viruses (parainfluenza, respiratory syncytial virus, and picornavirus) were examined in the Canadian Asthma Primary Prevention Study by using both an affected-only family-based transmission disequilibrium test and case-control methods.

RESULTS

In a joint analysis of all 4 cohorts, IL-1 receptor 2 (IL1R2) and Toll-like receptor 1 (TLR1) SNPs were associated with atopy after correction for multiple comparisons. In addition, an NFKBIA SNP was associated with atopic asthma. Six SNPs (rs1519309 [TLR3], rs740044 [ILIR2], rs4543123 [TLR1], rs5741812 [LBP], rs917998 [IL18RAP], and rs3136641 [NFKBIB]) were significant (P < .05, confirmed with 30,000 permutations) in both the combined analysis of main genetic effects and SNP-virus interaction analyses in both case-control and family-based methods. The TLR1 variant (rs4543123) was associated with both multiple viruses (respiratory syncytial virus and parainfluenza virus) and multiple phenotypes.

CONCLUSION

We have identified novel susceptibility genes for asthma and related traits and interactions between these genes and early-life viral infections.

High screen time is associated with asthma in overweight Manitoba youth

OBJECTIVE

Low physical activity and high sedentary behavior are associated with adverse health outcomes, including asthma. The purposes were to (1) determine if low physical activity and/or high screen time increase the risk of asthma and airway hyperresponsiveness (AHR) in youth and (2) determine if weight status modifies these associations.

METHODS

This is a prospective cohort study of healthy weight and overweight Canadian youth. In 2003-2005, 723 youth (8.6 ± 0.5 years; 34.0% asthma, 55.9% boys) were recruited from the 1995 Manitoba Prospective Cohort Study. In 2008-2010, 489 returned for follow-up measures (30.9% asthma, 56.6% boys). The primary exposure variables were parent-reported physical activity and screen time at 8-10 years of age. The primary outcome measures were pediatric allergist-defined asthma and AHR defined as the provocative concentration of methacholine required to induce a 20% fall in forced expiratory volume in 1 second (FEV(1)).

RESULTS

Low physical activity (≤2 times weekly) was not associated with asthma or AHR. However, high screen time (≥1 hour/day) was associated with a greater odds of asthma at baseline (odds ratio (OR) = 2.01, 95% confidence interval (CI) = 1.20-3.37, p < .01) and follow-up (OR = 2.11, 95% CI = 1.14-3.89, p < .02) versus low screen time. This association was more pronounced among overweight youth (baseline: OR = 3.95, 95% CI = 1.70-9.12, p < .0001; follow-up: OR = 3.22, 95% CI = 1.17-8.86, p < .02). Screen time was not associated with AHR at baseline or follow-up.

CONCLUSIONS

High screen time increases the risk of asthma, particularly among overweight youth. Screen time, in addition to physical activity, should be included in clinical assessments of youth with asthma.

Allostatic load biomarkers and asthma in adolescents

RATIONALE

Allostatic load (AL), a novel measure of the physiologically dysregulated response of the body to stress, represents a biomarker of chronic stress exposure.

OBJECTIVES

To determine whether preadolescent children with high AL are more susceptible to asthma as adolescents.

METHODS

This was a prospective evaluation of children recruited at 7 to 10 years of age in the nested case-control arm of the Study of Asthma, Genes and Environment and followed until 11 to 14 years of age. AL was measured using eight biomarkers: fasting glucose, total cholesterol, high-density lipoprotein cholesterol, dehydroepiandrosterone sulfate, cortisol, systolic and diastolic blood pressure, and waist-to-hip ratio. AL, created from the sum of biomarkers in a high-risk quartile, was related to prevalence and incidence of asthma using logistic regression.

MEASUREMENTS AND MAIN RESULTS

Among 352 participants followed until 11 to 14 years of age, prevalent asthma was four times more likely in boys with high (>3) versus low (≤2) AL after adjusting for current asthma/atopy, age, ethnicity, parental history of asthma, and overweight status. Similar results were observed in the analysis of new-onset asthma in boys (adjusted odds ratio, 4.35; 95% confidence interval, 1.19-15.9). In girls, there were no associations between AL and asthma. In the analysis of a subset of biomarkers, combinations of total cholesterol, glucose, and cortisol were associated with similar or greater risk of asthma prevalence or onset in boys.

CONCLUSIONS

AL and its biomarkers are associated with an increased likelihood of asthma in adolescent boys. The observed association between AL and asthma may be attributable to a combined subset of AL biomarkers.

Influence of socioeconomic status trajectories on innate immune responsiveness in children

OBJECTIVES

Lower socioeconomic status (SES) is consistently associated with poor health, yet little is known about the biological mechanisms underlying this inequality. In children, we examined the impact of early-life SES trajectories on the intensity of global innate immune activation, recognizing that excessive activation can be a precursor to inflammation and chronic disease.

METHODS

Stimulated interleukin-6 production, a measure of immune responsiveness, was analyzed ex vivo for 267 Canadian schoolchildren from a 1995 birth cohort in Manitoba, Canada. Childhood SES trajectories were determined from parent-reported housing data using a longitudinal latent-class modeling technique. Multivariate regression was conducted with adjustment for potential confounders.

RESULTS

SES was inversely associated with innate immune responsiveness (p=0.003), with persistently low-SES children exhibiting responses more than twice as intense as their high-SES counterparts. Despite initially lower SES, responses from children experiencing increasing SES trajectories throughout childhood were indistinguishable from high-SES children. Low-SES effects were strongest among overweight children (p<0.01). Independent of SES trajectories, immune responsiveness was increased in First Nations children (p<0.05) and urban children with atopic asthma (p<0.01).

CONCLUSIONS

These results implicate differential immune activation in the association between SES and clinical outcomes, and broadly imply that SES interventions during childhood could limit or reverse the damaging biological effects of exposure to poverty during the preschool years.

"Asthma isn't an excuse, it's just a condition": youths' perceptions of physical activity and screen time

OBJECTIVE

During puberty, physical activity patterns begin to decline, while sedentary time increases. These changes may be confounded by asthma. The purpose of this study was to gain insight into youths' perceptions of screen time and physical activity by asthma status.

METHODS

Four interviews and seven focus groups with boys only or girls only were conducted with 15- to 16-year-old youth enrolled in either of two asthma-focused cohorts in Manitoba, Canada. Using a semi-structured interview guide, youth were asked about their perceptions of physical activity and screen time such as texting, watching television, electronic games, and Internet chatting and about their perceptions of the influence that asthma has on these behaviors. Data were analyzed using thematic coding.

RESULTS

Two themes were common to youth with asthma and without asthma: (1) sports are an integral part of youths' lives and (2) screen time is important to youth. Two themes were identified among youth with asthma only: (1) physical activity used to be more difficult and (2) being active and living with asthma. Youth with asthma described physical activity as neither a hindrance to activity nor an excuse for inactivity, although asthma may still present some challenges. They also acknowledged their reliance on screen time for communication and for entertainment.

CONCLUSIONS

Youth with asthma believe that physical activity has become increasingly easier as they become older and that being active with asthma, despite its challenges, is a key part of their lives.

The association between community stressors and asthma prevalence of school children in Winnipeg, Canada

It is generally surmised that community stressors have an incubating effect for a variety of diagnoses on maternal and child health. This is of public health significance, as children of mothers facing long-term distress were found to have a 60% higher risk for asthma diagnosis at age 7 in Manitoba, Canada. Our objective was to determine the association of community stressors with childhood asthma prevalence in Winnipeg, Canada from participants who completed the Study of Asthma, Genes and the Environment (SAGE) survey administered in 2002–2003 to a birth cohort from 1995. Measures of community socioeconomic makeup and community disorder with rank ordinalized by quintile at the census tract level were obtained from the 1996 Canada Census. Crime data (annual incidence per 10,000 persons) by neighbourhood profile for 2001 was provided by the Winnipeg Police Service. Dichotomous caregiver report of child asthma along with other indicators from the geocoded SAGE survey allowed linkage to 23 neighbourhood profiles. Multilevel logistic regression analyses were performed to estimate the effect of community stressors on childhood asthma prevalence for birth and non-birth home children (N = 1472) and children resident of birth homes at age 7 or 8 (N = 698). After adjusting for individual risk factors, children resident of birth homes in a high thefts over $5,000 neighbourhood profile were twice as likely (Adjusted OR, 2.05; 95% CI, 1.11–3.81) to have report of asthma compared to children in a lower thefts over $5,000 profile, with community thefts over $5,000 explaining over half of the observed neighbourhood variation in asthma.

Body image and dieting attitudes among preadolescents

PURPOSE

Differences in body image and dieting concerns were assessed in preadolescent boys and girls across the body mass index (BMI) spectrum. The hypothesis was that girls would express more concern with body size, report more dieting, and receive more advice than boys.

METHODS

In this cross-sectional descriptive study, age-appropriate figure drawings, the Children's Eating Attitudes Test (ChEAT), the Restraint Scale, and the Body Esteem Scale were administered to participants in the Study of Asthma, Genes and Environment, Manitoba. Responses were compared between genders and correlated with BMI percentiles.

RESULTS

A total of 565 10- and 11-year-old children (321 boys) completed questionnaires. Overall, 39% of participants wanted to be thinner, and no significant gender differences based on weight were found. However, the use of figure drawings indicated that girls desired greater changes in body size (p=0.006). Girls had higher Restraint Scale scores (p=0.003), but no statistically significant differences were found in self-reported dieting, ChEAT, or Body Esteem Scale scores. Approximately 25% of children reported receiving frequent weight-related advice. Girls did not report this more often than did boys. Children in the lowest BMI percentile desired the greatest change in body shape and had the highest Restraint Scale scores.

CONCLUSIONS

Key gender differences underline the importance of understanding children's attitudes toward body image, weight, and dieting.

Administrative record linkage as a tool for public health research

Linked administrative databases offer a powerful resource for studying important public health issues. Methods developed and implemented in several jurisdictions across the globe have achieved high-quality linkages for conducting health and social research without compromising confidentiality. Key data available for linkage include health services utilization, population registries, place of residence, family ties, educational outcomes, and use of social services. Linking events for large populations of individuals across disparate sources and over time permits a range of research possibilities, including the capacity to study low-prevalence exposure-disease associations, multiple outcome domains within the same cohort of individuals, service utilization and chronic disease patterns, and life course and transgenerational transmission of health. Limited information on variables such as individual-level socioeconomic status (SES) and social supports is outweighed by strengths that include comprehensive follow-up, continuous data collection, objective measures, and relatively low expense. Ever advancing methodologies and data holdings guarantee that research using linked administrative databases will make increasingly important contributions to public health research.

Metabolomic profiling of asthma: diagnostic utility of urine nuclear magnetic resonance spectroscopy

BACKGROUND

The ability to diagnose and monitor asthma on the basis of noninvasive measurements of airway cellular dysfunction is difficult in the typical clinical setting.

OBJECTIVE

Metabolomics is the study of molecules created by cellular metabolic pathways. We hypothesized that the metabolic activity of children with asthma would differ from healthy children without asthma. Furthermore, children having an asthma exacerbation would be different compared with children with stable asthma in outpatient clinics. Finally, we hypothesized that (1)H-nuclear magnetic resonance (NMR) would measure such differences using urine samples, one of the least invasive forms of biofluid sampling.

METHODS

Children (135 total, ages 4-16 years) were enrolled, having met the criteria of healthy controls (C), stable asthma in the outpatient clinic (AO), or unstable asthma in the emergency department (AED). Partial least squares discriminant analysis was performed on the NMR data to create models of separation (70 metabolites were measured/urine sample). Some NMR data were withheld from modeling to be run blindly to determine possible diagnostic accuracy.

RESULTS

On the basis of the model of AO versus C, 31 of 33 AO samples were correctly diagnosed with asthma (94% accuracy). Only 1 of 20 C samples was incorrectly labeled as asthma (5% misclassification). On the basis of the AO versus AED model, 31 of the 33 AO samples were correctly diagnosed as outpatient asthma (94% accurate).

CONCLUSION

This is the first report suggesting that (1)H-NMR analysis of human urine samples has the potential to be a useful clinical tool for physicians treating asthma.

Depression is more common in girls with nonatopic asthma

BACKGROUND

Asthma may increase the risk of comorbid depressive disorders in children. Children suffering from asthma or depression are more often overweight. We examined whether depression was more likely in children with atopic and nonatopic asthma, independent of abdominal adiposity.

METHODS

A cross-sectional analysis was performed on data collected in the Study of Asthma, Genes, and Environment in Canada. Children aged 11 to 14 years were assessed by a pediatric allergist to confirm asthma, allergic rhinitis, and atopic dermatitis diagnosis. Atopic asthma was defined based on skin prick testing and allergic asthma based on the presence of allergic rhinitis or atopic dermatitis in addition to asthma. Depressive symptoms were assessed using the Children's Depression Inventory-Short Form. Data were analyzed using logistic regression modeling to determine likelihood of depression in children with asthma, stratified by gender and adjusting for ethnicity, waist circumference (WC), and atopy.

RESULTS

Four hundred thirty-one children aged 11 to 14 years (136 with asthma and 295 without asthma) were studied. After adjusting for the covariates, girls who had nonatopic or nonallergic asthma were three times more likely to have comorbid depressive symptoms compared with healthy girls (OR, 2.84; 95% CI, 1.00-8.10; OR, 3.47; 95% CI, 1.30-9.25, respectively). For each 10-cm increase in WC of girls, our model showed a 39% to 56% increase in the chance of depression. In boys, neither asthma nor WC showed an association with depression.

CONCLUSIONS

We recommend all health practitioners who see girls with asthma or girls who are overweight watch for depressive symptoms and treat comorbid depression seriously.

TLR4 Asp299Gly and Thr399Ile polymorphisms: no impact on human immune responsiveness to LPS or respiratory syncytial virus

Background

A broad variety of natural environmental stimuli, genotypic influences and timing all contribute to expression of protective versus maladaptive immune responses and the resulting clinical outcomes in humans. The role of commonly co-segregating Toll-like receptor 4 (TLR4) non-synonymous single nucleotide polymorphisms Asp299Gly and Thr399Ile in this process remains highly controversial. Moreover, what differential impact these polymorphisms might have in at risk populations with respiratory dysfunction, such as current asthma or a history of infantile bronchiolitis, has never been examined. Here we determine the importance of these polymorphisms in modulating LPS and respiratory syncytial virus (RSV) - driven cytokine responses. We focus on both healthy children and those with clinically relevant respiratory dysfunction.

Methodology

To elucidate the impact of TLR4 Asp299Gly and Thr399Ile on cytokine production, we assessed multiple immune parameters in over 200 pediatric subjects aged 7–9. Genotyping was followed by quantification of pro- and anti-inflammatory cytokine responses by fresh peripheral blood mononuclear cells upon acute exposure to LPS or RSV.

Principal Findings

In contrast to early reports, neither SNP influenced immune responses evoked by LPS exposure or RSV infection, as measured by the intermediate phenotype of pro- and anti-inflammatory cytokine responses to these ubiquitous agents. There is no evidence of altered sensitivity in populations with “at risk” clinical phenotypes.

Conclusions/Significance

Genomic medicine seeks to inform clinical practice. Determination of the TLR4 Asp299Gly/Thr399Ile haplotype is of no clinical benefit in predicting the nature or intensity of cytokine production in children whether currently healthy or among specific at-risk groups characterized by prior infantile broncholitis or current asthma.

Lack of association of TIM3 polymorphisms and allergic phenotypes

Background

T-cell immunoglobulin mucin-3 (TIM3) is a T_H1-specific type 1 membrane protein that regulates T_H1 proliferation and the development of immunological tolerance. TIM3 and its genetic variants have been suggested to play a role in regulating allergic diseases. Polymorphisms in the TIM3 promoter region have been reported to be associated with allergic phenotypes in several populations. The aims of this study were to examine whether genetic variation in the promoter region of TIM3 influenced transcription of the gene and risk for allergic phenotypes.

Methods

We performed 5' rapid amplification of cDNA ends and reverse transcription-polymerase chain reaction. We screened for polymorphisms in the promoter region. Deletion analysis was used to localize the promoter region of TIM3. Genotyping was performed by TaqMan assays in three asthma/allergy population samples.

Results

We found two regions with promoter activity in TIM3. One region was from -214 bp to +58 bp and the other from -1.6 kb to -914 bp relative to the transcription start site. None of the single nucleotide polymorphisms (SNPs) or haplotypes affected the transcriptional activity in reporter gene assays. No association between the SNPs and any phenotype was observed in the study cohorts.

Conclusion

Our findings indicate that SNPs and haplotypes in the TIM3 promoter region do not have a functional effect in vitro and are not associated with allergic diseases. These data suggest that polymorphisms in the TIM3 promoter region are unlikely to play an important role in susceptibility to allergic diseases.

Antibiotic use in children is associated with increased risk of asthma

BACKGROUND

Antibiotic exposure in early childhood is a possible contributor to the increasing asthma prevalence in industrialized countries. Although a number of published studies have tested this hypothesis, the results have been conflicting.

OBJECTIVE

To explore the association between antibiotic exposure before 1 year of age and development of childhood asthma.

METHODS

Using administrative data, birth cohorts from 1997 to 2003 were evaluated (N = 251817). Antibiotic exposure was determined for the first year of life. After the first 24 months of life, the incidence of asthma was determined in both those exposed and not exposed to antibiotics in the first 12 months of life. Cox proportional hazards models were used to adjust for potential confounders and determine the hazard ratios associated with antibiotic exposure for the development of asthma.

RESULTS

Antibiotic exposure in the first year of life was associated with a small risk of developing asthma in early childhood after adjusting for gender, socioeconomic status at birth, urban or rural address at birth, birth weight, gestational age, delivery method, frequency of physician visits, hospital visit involving surgery, visits to an allergist, respirologist, or immunologist, congenital anomalies, and presence of otitis media, acute, or chronic bronchitis, and upper and lower respiratory tract infections during the first year of life. As the number of courses of antibiotics increased, this was associated with increased asthma risk, with the highest risk being in children who received >4 courses. All antibiotics were associated with an increased risk of developing asthma, with the exception of sulfonamides.

CONCLUSIONS

This study provides evidence that the use of antibiotics in the first year of life is associated with a small risk of developing asthma, and this risk increases with the number of courses of antibiotics prescribed.