Risk of physician-diagnosed asthma in the first 6 years of life

Antiasthmatic prescriptions in children with and without congenital anomalies: a population-based study

OBJECTIVES

To explore the risk of being prescribed/dispensed medications for respiratory symptoms and breathing difficulties in children with and without congenital anomalies.

DESIGN

A EUROlinkCAT population-based data linkage cohort study. Data on children with and without congenital anomalies were linked to prescription databases to identify children who did/did not receive antiasthmatic prescriptions. Data were analysed by age, European region, class of antiasthmatic, anomaly, sex, gestational age and birth cohort.

SETTING

Children born 2000-2014 in six regions within five European countries.

PARTICIPANTS

60 662 children with congenital anomalies and 1 722 912 reference children up to age 10 years.

PRIMARY OUTCOME MEASURE

Relative risks (RR) of >1 antiasthmatic prescription in a year, identified using Anatomical Therapeutic Chemical classification codes beginning with R03.

RESULTS

There were significant differences in the prescribing of antiasthmatics in the six regions. Children with congenital anomalies had a significantly higher risk of being prescribed antiasthmatics (RR 1.41, 95% CI 1.35 to 1.48) compared with reference children. The increased risk was consistent across all regions and all age groups. Children with congenital anomalies were more likely to be prescribed beta-2 agonists (RR 1.71, 95% CI 1.60 to 1.83) and inhaled corticosteroids (RR 1.74, 95% CI 1.61 to 1.87). Children with oesophageal atresia, genetic syndromes and chromosomal anomalies had over twice the risk of being prescribed antiasthmatics compared with reference children. Children with congenital anomalies born <32 weeks gestational age were over twice as likely to be prescribed antiasthmatics than those born at term (RR 2.20, 95% CI 2.10 to 2.30).

CONCLUSION

This study documents the additional burden of respiratory symptoms and breathing difficulties for children with congenital anomalies, particularly those born preterm, compared with children without congenital anomalies in the first 10 years of life. These findings are beneficial to clinicians and healthcare providers as they identify children with greater morbidity associated with respiratory symptoms, as indicated by antiasthmatic prescriptions.

Geographical Differences of Risk of Asthma and Allergic Rhinitis according to Urban/Rural Area: a Systematic Review and Meta-analysis of Cohort Studies

Several studies have demonstrated an association between the risk asthma/allergic rhinitis and the environment. However, to date, no systematic review or meta-analysis has investigated these factors. We conducted a systematic review and meta-analysis to assess the association between urban/rural living and the risk of asthma and allergic rhinitis. We searched the Embase and Medline databases for relevant articles and included only cohort studies to observe the effects of time-lapse geographical differences. Papers containing information on rural/urban residence and respiratory allergic diseases were eligible for inclusion. We calculated the relative risk (RR) and 95% confidence interval (CI) using a 2 × 2 contingency table and used random effects to pool data. Our database search yielded 8388 records, of which 14 studies involving 50,100,913 participants were finally included. The risk of asthma was higher in urban areas compared to rural areas (RR, 1.27; 95% CI, 1.12-1.44, p < 0.001), but not for the risk of allergic rhinitis (RR, 1.17; 95% CI, 0.87-1.59, p = 0.30). The risk of asthma in urban areas compared to rural areas was higher in the 0-6 years and 0-18 years age groups, with RRs of 1.21 (95% CI, 1.01-1.46, p = 0.04) and 1.35 (95% CI, 1.12-1.63, p = 0.002), respectively. However, there was no significant difference in the risk of asthma between urban and rural areas for children aged 0-2 years, with a RR of 3.10 (95% CI, 0.44-21.56, p = 0.25). Our study provides epidemiological evidence for an association between allergic respiratory diseases, especially asthma, and urban/rural living. Future research should focus on identifying the factors associated with asthma in children living in urban areas. The review was registered in PROSPERO (CRD42021249578).

Early-Life Antibiotic Exposure and Childhood Asthma Trajectories: A National Population-Based Birth Cohort

INTRODUCTION

Early-life antibiotic exposure is common and impacts the development of the child's microbiome and immune system. Information on the impacts of early-life antibiotics exposure on childhood asthma is lacking.

METHODS

This study examined associations between early-life (0-24 months) antibiotics exposure with childhood (6-15 years) asthma trajectories through the Australian Longitudinal Study of Australian Children (LSAC) and their linked data from the Pharmaceutical Benefits Scheme. Asthma phenotypes were derived by group-based trajectory modeling.

RESULTS

Of 5107 LSAC participants, 4318 were included in the final analyses (84.6% retention). Four asthma phenotypes were identified: Always-low-risk (79.0%), early-resolving asthma (7.1%), early-persistent asthma (7.9%), and late-onset asthma (6.0%). Any early-life antibiotic exposure increased risk 2.3-fold (95% CI: 1.47-3.67; p < 0.001) for early-persistent asthma among all children. In subgroup analyses, early-persistent asthma risk increased by 2.7-fold with any second-generation cephalosporin exposure, and by 2-fold with any β-lactam other than cephalosporin or macrolide exposure.

CONCLUSION

We concluded that early-life antibiotic exposure is associated with an increased risk of early-persistent childhood asthma. This reinforces scrutiny of early-life antibiotic use, particularly for common viral infections where no antibiotics are required.

Growth pattern during early infancy, body mass index during childhood and childhood asthma

BACKGROUND

There is a lack of longitudinal studies of associations between growth from infancy to childhood and asthma development.

OBJECTIVE

The objective of the study was to investigate the effects of weight change during infancy, body mass index (BMI) and the interaction of these factors on the risk of childhood asthma.

METHODS

We enrolled children born in 2008 and 2009 at full-term and with normal birth weight. The weight change in infancy was grouped into slow, on-track and rapid. BMI status in childhood was stratified into low, normal and high groups and used as a time-varying variable. The outcome was asthma, defined as two or more diagnoses of asthma separated by at least 1 year after 2 years of age. The risk of asthma was assessed using Cox proportional hazard regression, with adjustment for sex, residence area at birth, economic status and feeding types in infancy.

RESULTS

Of 917,707 children born in Korea in 2008 and 2009, 271,871 were eligible for analysis. The risk of asthma was greater in groups with low birth weight (aHR 1.06, 95% CI 1.04 to 1.08), rapid body weight change during early infancy (aHR 1.08, 95% CI 1.07 to 1.10) and high BMI during childhood (aHR 1.06, 95% CI 1.04-1.08). The interaction of weight change during early infancy with BMI during childhood was significant for asthma (p < .01). Rapid weight gain in infancy was associated with lower risk of asthma in those with low BMI during childhood; had no association with asthma in those with normal BMI during childhood; and was associated increased asthma risk in those with high BMI during childhood-aHR 1.26 (95% CI 1.19 to 1.33) and aHR 1.33 (95% CI 1.12 to 1.56) compared with on-track and slow infant weight gain, respectively.

CONCLUSION

Low birth weight, high BMI during childhood and, in those with high childhood BMI, rapid weight gain during early infancy are associated with increased risk of childhood asthma.

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.

Maternal Distress During Pregnancy and Recurrence in Early Childhood Predicts Atopic Dermatitis and Asthma in Childhood

BACKGROUND

Early-life stress is becoming an important determinant of immune system programming. Maternal prenatal distress is found to be associated with atopic disease in offspring but the separate effects of postnatal distress are not well-studied.

RESEARCH QUESTION

Does the likelihood of asthma and atopic dermatitis in children increase when they are exposed to maternal distress pre- and postnatally in a sex-specific manner?

STUDY DESIGN AND METHODS

Using data from a provincial newborn screen and health-care database for 12,587 children born in 2004, maternal distress (depression or anxiety) was defined as prenatal, self-limiting, recurrent, or late-onset postpartum. Atopic dermatitis (AD) and asthma at ages 5 years and 7 years of age were diagnosed by using hospitalization, physician visit, or prescription records. Associations between maternal distress and childhood asthma and AD were determined by using multiple logistic regression.

RESULTS

After adjusting for risk factors, a significant association between maternal prenatal (OR, 1.27; 95% CI, 1.11-1.46), recurrent postpartum (OR, 1.28; 95% CI, 1.11-1.48), and late-onset postpartum (OR, 1.19, 95% CI, 1.06-1.34) distress was found with AD at age 5 years. Asthma at age 7 years was also associated with maternal prenatal distress (OR, 1.57; 95% CI, 1.29-1.91) and late-onset postnatal distress (OR, 1.22; 95% CI, 1.01-1.46). Self-limiting postnatal distress was not found to be a risk factor for either atopic condition. Associations with AD or asthma were of a similar magnitude in boys and girls; the exception was recurrent postnatal distress, which increased risk for asthma in boys only.

INTERPRETATION

This population-based study provides evidence for sex-specific associations between maternal prenatal and postnatal distress, as well as the development of AD and asthma. The findings support recommendations for greater psychosocial support of mothers during pregnancy and early childhood to prevent childhood atopic disease.

Maternal history of asthma modifies the risk of childhood persistent asthma associated with maternal age at birth: Results from a large prospective cohort in Canada

BACKGROUND

Asthma is a prevalent disease that affects many Canadians. Persistent asthma can affect quality of life, and has multiple health implications. Maternal age at birth has been associated with many adverse health outcomes in children. Conflicting study results exist regarding maternal age at birth and childhood asthma. The association between maternal age at birth and persistent asthma in children is still unknown.

OBJECTIVE

To investigate the relationship between maternal age at birth and persistent asthma in children at ten years of age.

METHODS

This is a prospective cohort study including all children aged 0-2 years who took part in the first cycle of the National Longitudinal Survey of Children and Youths (NLSCY) and were followed every two years until eight to ten years of age in Cycle 5. An interaction term between maternal age at birth and maternal asthma history was introduced in a multivariate model to examine modification effects of maternal asthma history on the association.

RESULTS

Multivariate logistic regression demonstrated that older maternal age at birth was significantly associated with an increased risk of childhood persistent asthma in mothers with a history of asthma (OR = 1.20, 95% CI: 1.04-1.40, p = .016). No relationship was found in mothers without a history of asthma.

CONCLUSION

Maternal history of asthma has an impact on the association between maternal age at birth and childhood persistent asthma in children by age ten. The finding may help explain the inconsistent results in the literature regarding the risk of asthma associated with maternal age at birth.

Diet and asthma in Lebanese schoolchildren: A cross-sectional study

OBJECTIVES

The causes of the global increase in asthma in children are unknown. It has been hypothesized that diet is an important factor that may play a role in the pathogenesis of the disease. The objective was to evaluate the association between diet and current asthma among Lebanese children.

METHODS

A cross-sectional study was conducted on 1000 children recruited from public and private schools in Lebanon. Of the total enrolled participants, 107 children were diagnosed with current asthma and were analyzed. The food frequency questionnaire was used to assess participants' dietary habits.

RESULTS

The consumption of sweets ≥3 times weekly (ORa = 5.42), white bread ≥3 times weekly (ORa = 26.38), and olive oil daily (ORa = 9.80) were associated with higher odds of current asthma. Drinking carbonated beverages occasionally (ORa = 0.25) and ≥3 times per week (ORa = 0.03) was significantly associated with lower odds of current asthma. Adhering to Mediterranean diet (occasional, >3 times weekly and daily) was significantly associated with lower odds of current asthma compared to never consuming Mediterranean diet (ORa = 0.23 and ORa = 0.22, respectively). The occasional consumption of bread was significantly associated with higher odds of current asthma (ORa = 8.2), whereas daily consumption was significantly associated with lower odds (ORa = 0.336). Moreover, the occasional, ≥3 times weekly and daily consumption of meat were significantly associated with higher odds of current asthma (ORa = 9.6; ORa = 5.1 and ORa = 4.5), respectively. An occasional consumption of junk food was significantly associated with lower odds of current asthma (ORa = 0.044), whereas a daily consumption was associated with higher odds.

CONCLUSION

Adhering to certain diets might be associated with higher odds of current asthma.

Association between Traffic Related Air Pollution and the Development of Asthma Phenotypes in Children: A Systematic Review

Introduction

Traffic related air pollution (TRAP) has long been associated with the onset of childhood asthma. The relationship between TRAP exposure and the development of childhood asthma phenotypes is less understood. To better understand this relationship, we performed a systematic review of the literature studying childhood TRAP exposure and the development of childhood asthma and wheezing phenotypes (transient, persistent, and late-onset asthma/wheezing phenotypes).

Methods

A literature search was performed in PubMed, Embase, and Scopus databases for current literature, returning 1706 unique articles. After screening and selection, 7 articles were included in the final review. Due to the low number of articles, no meta-analysis was performed.

Results

TRAP exposure appears to be associated with both transient and persistent asthma/wheezing phenotypes. However, there was little evidence to suggest a relationship between TRAP exposure and late-onset asthma/wheezing. The differing results may be in part due to the heterogeneity in study methods and asthma/wheezing phenotype definitions, in addition to other factors such as genetics.

Conclusion

TRAP exposure may be associated with transient and persistent asthma/wheezing phenotypes in children. The low number of studies and differing results suggest that further studies are warranted.

Gestational age at birth and wheezing trajectories at 3-11 years

OBJECTIVE

Children born preterm have an increased risk of asthma in early childhood. We examined whether this persists at 7 and 11 years, and whether wheezing trajectories across childhood are associated with preterm birth.

DESIGN

Data were from the UK Millennium Cohort Study, which recruited children at 9 months, with follow-up at 3, 5, 7 and 11 years.

OUTCOMES

Adjusted ORs (aOR) were estimated for recent wheeze and asthma medication use for children born <32, 32-33, 34-36 and 37-38 weeks' gestation, compared with children born at full term (39-41 weeks) at 7 (n=12 198) and 11 years (n=11 690). aORs were also calculated for having 'early-remittent' (wheezing at ages 3 and/or 5 years but not after), 'late' (wheezing at ages 7 and/or 11 years but not before) or 'persistent/relapsing' (wheezing at ages 3 and/or 5 and 7 and/or 11 years) wheeze.

RESULTS

Birth <32 weeks, and to a lesser extent at 32-33 weeks, were associated with an increased risk of wheeze and asthma medication use at ages 7 and 11, and all three wheezing trajectories. The aOR for 'persistent/relapsing wheeze' at <32 weeks was 4.30 (95% CI 2.33 to 7.91) and was 2.06 (95% CI 1.16 to 2.69) at 32-33 weeks. Birth at 34-36 weeks was not associated with asthma medication use at 7 or 11, nor late wheeze, but was associated with the other wheezing trajectories. Birth at 37-38 weeks was not associated with wheeze nor asthma medication use.

CONCLUSIONS

Birth <37 weeks is a risk factor for wheezing characterised as 'early-remittent' or 'persistent/relapsing' wheeze.

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Associations between sensitization to perennial/seasonal allergens and childhood asthma

Background: Childhood asthma is an important public health problem worldwide. Risk factors for asthma development include allergic sensitization and exposure to animals. Objective: To identify which (perennial or seasonal) inhalant allergens are associated with asthma and allergic rhinitis in children. Methods: This was a cross-sectional, retrospective study. We evaluated data from medical documentation of 6,000 children (aged 6 – 18 years) with diagnosed asthma and/or allergic rhinitis who had attended our allergy outpatient clinic. Into the analyses we included those subjects who had specific IgE test done during diagnostic procedures to confirm allergen sensitization. Results: We included 5,076 children in the analysis. We showed that among seasonal allergens only sensitization to timothy or birch significantly changed the prevalence of allergic rhinitis and asthma diagnosis. Of the perennial allergens, house dust mite or cat were most closely related with both allergic rhinitis and asthma. Results of ROC curve analysis showed that in atopic children the specific IgE level of seasonal allergens did not significantly change the prevalence of asthma diagnosis. Sensitization to more than one perennial allergen significantly increased the prevalence of allergic rhinitis and asthma. Conclusion: We showed that sensitization to the seasonal allergens timothy and birch as well as to the perennial allergens house dust mite and cat, is associated with asthma and allergic rhinitis in children. Our study determined the role of multiple perennial indoor allergens in the developement of allergic diseases in children. The identification of the specific allergens makes them potential targets for intervention and prevention strategies.

Twins' risk of childhood asthma mediated by gestational age and birthweight

BACKGROUND

Children born with low gestational age (GA) or low birthweight (BW) are at increased risk of asthma. Twins as compared to singletons are on average more likely to be born with lower GA and BW and have been hypothesized to comprise a high-risk population for asthma. Many previous studies have not accounted for potential confounders or mediators.

OBJECTIVE

To investigate the association between twinship and childhood asthma or early life wheeze and identify potential mediators, such as GA/BW.

METHODS

The study population consisted of two cohorts including all children born in Sweden from 1 January 1993 to 1 June 2001 (n = 756,363 singletons, n = 22,478 twins) and 1 July 2005 to 31 December 2009 (n = 456,239 singletons, n = 12,872 twins). Asthma was defined using validated register-based outcomes of diagnosis or medication. The data were analysed using logistic (older cohort) and Cox regression (younger cohort). Adjusted models incorporated potential confounding or mediating factors including gestational age and birthweight.

RESULTS

In the younger cohort, the crude hazard ratio (HR) of asthma medication after 1.5 years of age was 1.12 (95% CI 1.01-1.23), and fully adjusted HR was 0.80, 95% CI 0.72-0.89. Crude HR of asthma diagnosis in the same age group was 1.14 (95% CI 0.99-1.30), fully adjusted 0.78 (0.68-0.98). Adjusted analyses in the older group yielded similar results.

CONCLUSIONS

Twins were at significantly higher unadjusted risk of asthma or early life wheeze compared to singletons in the younger, but not in the older cohort. Associations attenuated following adjustment for GA/BW, suggesting that GA/BW mediates the effect of twinship on asthma risk. After adjustments, twins were at lower risk of asthma outcomes, possibly due to unmeasured confounding.

Social inequalities in wheezing in children: findings from the UK Millennium Cohort Study

Wheezing in childhood is socially patterned, but it is unclear what factors explain the social differences.Regression analysis of the UK Millennium Cohort Study, based on 11 141 singleton children who participated at ages 9 months and 3, 5 and 7 years. Relative risk ratios (RRR) for early and persistent/relapsing wheeze were estimated using multinomial regression, according to measures of socioeconomic circumstances. Maternal, antenatal and early-life characteristics were assessed as potential mediators.Children of mothers with no educational qualifications were more likely to have both wheeze types, compared to children of mothers with degree-level qualifications (RRR 1.53, 95% CI 1.26-1.86 for early wheeze; 1.32 95% CI 1.04-1.67 for persistent/relapsing wheeze). Controlling for maternal age, smoking during pregnancy and breastfeeding removed the elevated risk of wheezing. Male sex, maternal age, body mass index, atopy, smoking during pregnancy, preterm birth, breastfeeding, exposure to other children and furry pets were independently associated with wheezing, but the pattern of association varied between wheezing types.In this representative UK cohort, adjustment for maternal smoking during pregnancy and breastfeeding removed the socioeconomic inequalities in common wheezing phenotypes. Policies to reduce the social gradient in these risk factors may reduce inequalities in wheezing and asthma.

Time trends in the incidence, prevalence and age at diagnosis of asthma in children

BACKGROUND

Current knowledge on the prevalence of asthma is mainly based on cross-sectional questionnaire data. Current population-based data on the incidence of asthma in children are scarce.

OBJECTIVE

To study the incidence, prevalence, and age at diagnosis of asthma in children in the Netherlands over the study period 2000-2012.

METHODS

A population-based cohort study was conducted in the Integrated Primary Care Information database. The cohort consisted of 176,516 children (379,536 personyears (PY) of follow-up), aged 5-18 years between 2000 and 2012. All medical records of children with physician diagnosed asthma were validated. Incidence rates, annual percent change (APC), and prevalence for asthma were calculated. Influence of age and gender on incidence rates and change in age at diagnosis were studied.

RESULTS

We identified an asthma cohort of 14,303 children with 35,118 PY. The overall incidence rate was 6.7/1000 PY (95% CI, 6.45-6.97). Until 2008, the incidence rate was significantly increasing (APC 5.79 (95% CI 1.43-10.34); from 2008 onwards, a non-significant decrease was observed (APC -12.16 (95% CI -23.07 to 0.28). Incidence for girls was lower than for boys, this difference decreased with increasing age. (p < 0.001) Overall, the age at diagnosis increased over calendar time and was lower for boys. (linear trend p < 0.001).

CONCLUSION

Our population-based cohort study observed an incidence rate of 6.7 per 1000 PY of physician-diagnosed asthma in children in the Netherlands over 2000-2012. The asthma incidence rate was increasing until 2008. Further studies are needed to confirm the decrease in asthma incidence rate from 2008 onwards.

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

Background

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

Objective

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

Methods

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

Results

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

Conclusions

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

Persistent pollen exposure during infancy is associated with increased risk of subsequent childhood asthma and hayfever

BACKGROUND

Few studies have focused on pollen exposure and asthma in children. None have examined associations between persistent exposure to pollen in infancy and aeroallergen sensitisation and asthma in childhood.

OBJECTIVES

To examine the association between higher ambient levels of pollen in the first 3-6 months of life and risk of eczema, sensitization to food and aeroallergens at 2 years and asthma or hayfever at age 6-7 years combined.

METHODS

Using a birth cohort of 620 infants with a family history of allergic disease born between 1990 and 1994, we examined risk of eczema or allergic sensitization (SPT > 3 mm to at least one of cow's milk, egg white, peanut, house dust-mite, rye grass, and cat dander) by age 2 and asthma or hayfever at age 6-7. Daily ambient levels of pollen were measured during this period.

RESULTS

Cumulative exposure to pollen concentrations up to 6 months was associated with aeroallergen sensitization with the highest risk occurring at 3 months (aOR = 1.34, 95% CI 1.06-1.72). Cumulative exposure to pollen up to 3 months was also associated with hayfever (aOR = 1.14, 95% CI 1.009-1.29) and between 4 and 6 months exposure with asthma only (aOR=1.35, 95% CI 1.07-1.72).

CONCLUSION

Persistent pollen exposure in infancy appears to increase the risk of asthma and hayfever in children. These results support the hypothesis that there is a critical window of opportunity in early development which may be important for modification of allergic outcomes.

The relationship of season of birth to asthma and allergy in urban African American children from 10 to 13 years of age

OBJECTIVES

To assess the relationship between season of birth and presence of asthma and allergy in preteen, low-income, African American children.

METHODS

The study consisted of a self-administered survey followed by telephone interviews of parents of children attending 19 middle schools in Detroit, Michigan. Out of 4194 children, 1292 were identified with asthma and 962 parents of these children provided informed consent and took part in telephone interviews.

RESULTS

No statistically significant relationships were observed between season of birth and diagnosis of asthma (p > .05) or with diagnosis adjusting for income, age, gender, parent's education, or parent being a smoker (p > .05). No statistically significant association was evident between season of birth and presence of allergy (p > .05) or with allergy adjusting for the above variables (p > .05).

CONCLUSIONS

Identifying children vulnerable to problems with asthma and allergy, especially in populations exhibiting high prevalence of the conditions and significant disparities in outcomes, requires use of all possible means. Season of birth does not appear to be a useful indicator in identification of such children. The findings from this study do not support the proposition that season of birth, associated with early exposure to viruses as evident in the winter and to seasonal allergens, contributes to more asthma and/or allergy.

Fetal growth and risk of childhood asthma and allergic disease

Introduction

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

Objective

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

Methods

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

Results

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

Conclusion and clinical relevance

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

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The population attributable fraction of asthma among Canadian children

OBJECTIVE

We calculated the population attributable fraction (PAF) of Canadian childhood asthma due to modifiable environmental exposures, in order to estimate their relative contributions to asthma development based on the current literature.

METHODS

We conducted a systematic review to determine Canadian childhood asthma incidence, Canadian prevalence of exposure to airborne pollutants and indoor allergens, and international estimates of the risk of developing physician-diagnosed asthma (PDA) associated with each exposure. Combining risk estimates by meta-analysis where possible, PAF was calculated by the formula: PAF = Attributable risk *Exposure prevalence* 100%/Asthma incidence.

SYNTHESIS

Age-specific Canadian childhood asthma incidence ranged from 2.8%-6.9%. Canadian exposure prevalences were: PM10 16%, PM2.5 7.1%, NO2 25%, environmental tobacco smoke (ETS) 9.0%, cat 22%, dog 12%, mouse 17%, cockroach 9.8%, dust mite 30%, moisture 14% and mould 33%. Relative risk estimates of PDA were: PM10 1.64, PM2.5 1.44, NO2 1.29, ETS 1.40, mouse 1.23, cockroach 1.96, and spanned 1.00 for cat, dog, dust mites, moisture and mould. PAF estimates for incident asthma among preschool children were: PM10 11%, PM2.5 1.6%, NO2 4.0%, ETS 2.9%, mouse 6.5% and cockroach 13%.

CONCLUSIONS

This systematic review suggests contributions to childhood asthma development from exposure to particulates, NO2, ETS, mouse and cockroach. The associations appeared to be more complex for cat, dog and dust mite allergens and more variable for mould and moisture. Additional prospective, population-based studies of childhood asthma development with objectively-measured exposures are needed to further quantify these associations.

Maternal smoking during pregnancy, prematurity and recurrent wheezing in early childhood

BACKGROUND

Prenatal maternal smoking and prematurity independently affect wheezing and asthma in childhood.

OBJECTIVE

We sought to evaluate the interactive effects of maternal smoking and prematurity upon the development of early childhood wheezing.

METHODS

We evaluated 1,448 children with smoke exposure data from a prospective urban birth cohort in Boston. Maternal antenatal and postnatal exposure was determined from standardized questionnaires. Gestational age was assessed by the first day of the last menstrual period and early prenatal ultrasound (preterm < 37 weeks gestation). Wheezing episodes were determined from medical record extraction of well and ill/unscheduled visits. The primary outcome was recurrent wheezing, defined as ≥ 4 episodes of physician documented wheezing. Logistic regression models and zero inflated negative binomial regression (for number of episodes of wheeze) assessed the independent and joint association of prematurity and maternal antenatal smoking on recurrent wheeze, controlling for relevant covariates.

RESULTS

In the cohort, 90 (6%) children had recurrent wheezing, 147 (10%) were exposed to in utero maternal smoke and 419 (29%) were premature. Prematurity (odds ratio [OR] 2.0; 95% confidence interval [CI], 1.3-3.1) was associated with an increased risk of recurrent wheezing, but in utero maternal smoking was not (OR 1.1, 95% CI 0.5-2.4). Jointly, maternal smoke exposure and prematurity caused an increased risk of recurrent wheezing (OR 3.8, 95% CI 1.8-8.0). There was an interaction between prematurity and maternal smoking upon episodes of wheezing (P = 0.049).

CONCLUSIONS

We demonstrated an interaction between maternal smoking during pregnancy and prematurity on childhood wheezing in this urban, multiethnic birth cohort.

Determinants of asthma after severe respiratory syncytial virus bronchiolitis

BACKGROUND

The development of asthma after respiratory syncytial virus (RSV) bronchiolitis has been demonstrated in case-control studies, although the determinants of post-RSV asthma remain undefined.

OBJECTIVES

We sought to evaluate the potential determinants of physician-diagnosed asthma after severe RSV bronchiolitis during infancy.

METHODS

We enrolled 206 children during an initial episode of severe RSV bronchiolitis at 12 months of age or less in a prospective cohort study and followed these children for up to 6 years. In a subset of 81 children, we analyzed CCL5 (RANTES) mRNA expression in upper airway epithelial cells.

RESULTS

Forty-eight percent of children had physician-diagnosed asthma before the seventh birthday. Independent determinants significantly associated with increased risk for physician-diagnosed asthma by the seventh birthday included maternal asthma (odds ratio [OR], 5.2; 95% CI, 1.7-15.9; P = .004), exposure to high levels of dog allergen (OR, 3.2; 95% CI, 1.3-7.7; P = .012), aeroallergen sensitivity at age 3 years (OR, 10.7; 95% CI, 2.1-55.0; P = .005), recurrent wheezing during the first 3 years of life (OR, 7.3; 95% CI, 1.2-43.3; P = .028), and CCL5 expression in nasal epithelia during acute RSV infection (OR, 3.8; 95% CI, 1.2-2.4; P < .001). White children (OR, 0.19; 95% CI, 0.04-0.93; P = .041) and children attending day care (OR, 0.18; 95% CI, 0.04-0.84; P = .029) had a decreased risk of physician-diagnosed asthma.

CONCLUSIONS

Approximately 50% of children who experience severe RSV bronchiolitis have a subsequent asthma diagnosis. The presence of increased CCL5 levels in nasal epithelia at the time of bronchiolitis or the development of allergic sensitization by age 3 years are associated with increased likelihood of subsequent asthma.

Comparing exposure assessment methods for traffic-related air pollution in an adverse pregnancy outcome study

BACKGROUND

Previous studies reported adverse impacts of traffic-related air pollution exposure on pregnancy outcomes. Yet, little information exists on how effect estimates are impacted by the different exposure assessment methods employed in these studies.

OBJECTIVES

To compare effect estimates for traffic-related air pollution exposure and preeclampsia, preterm birth (gestational age less than 37 weeks), and very preterm birth (gestational age less than 30 weeks) based on four commonly used exposure assessment methods.

METHODS

We identified 81,186 singleton births during 1997-2006 at four hospitals in Los Angeles and Orange Counties, California. Exposures were assigned to individual subjects based on residential address at delivery using the nearest ambient monitoring station data [carbon monoxide (CO), nitrogen dioxide (NO(2)), nitric oxide (NO), nitrogen oxides (NO(x)), ozone (O(3)), and particulate matter less than 2.5 (PM(2.5)) or less than 10 (PM(10))μm in aerodynamic diameter], both unadjusted and temporally adjusted land-use regression (LUR) model estimates (NO, NO(2), and NO(x)), CALINE4 line-source air dispersion model estimates (NO(x) and PM(2.5)), and a simple traffic-density measure. We employed unconditional logistic regression to analyze preeclampsia in our birth cohort, while for gestational age-matched risk sets with preterm and very preterm birth we employed conditional logistic regression.

RESULTS

We observed elevated risks for preeclampsia, preterm birth, and very preterm birth from maternal exposures to traffic air pollutants measured at ambient stations (CO, NO, NO(2), and NO(x)) and modeled through CALINE4 (NO(x) and PM(2.5)) and LUR (NO(2) and NO(x)). Increased risk of preterm birth and very preterm birth were also positively associated with PM(10) and PM(2.5) air pollution measured at ambient stations. For LUR-modeled NO(2) and NO(x) exposures, elevated risks for all the outcomes were observed in Los Angeles only--the region for which the LUR models were initially developed. Unadjusted LUR models often produced odds ratios somewhat larger in size than temporally adjusted models. The size of effect estimates was smaller for exposures based on simpler traffic density measures than the other exposure assessment methods.

CONCLUSION

We generally confirmed that traffic-related air pollution was associated with adverse reproductive outcomes regardless of the exposure assessment method employed, yet the size of the estimated effect depended on how both temporal and spatial variations were incorporated into exposure assessment. The LUR model was not transferable even between two contiguous areas within the same large metropolitan area in Southern California.

Effects of secondhand smoke exposure on the health and development of african american premature infants

Objective. To explore the effects of secondhand smoke exposure on growth, health-related illness, and child development in rural African American premature infants through 24 months corrected age. Method. 171 premature infants (72 boys, 99 girls) of African American mothers with a mean birthweight of 1114 grams. Mothers reported on household smoking and infant health at 2, 6, 12, 18, and 24 months corrected age. Infant growth was measured at 6, 12, 18, and 24 months, and developmental assessments were conducted at 12 and 24 months. Results. Thirty percent of infants were exposed to secondhand smoke within their first 2 years of life. Secondhand smoke exposure was associated with poorer growth of head circumference and the development of otitis media at 2 months corrected age. Height, weight, wheezing, and child development were not related to secondhand smoke exposure. Conclusion. Exposure to secondhand smoke may negatively impact health of rural African American premature infants. Interventions targeted at reducing exposure could potentially improve infant outcomes.

Risk of asthma in young adults who were born preterm: a Swedish national cohort study

OBJECTIVE

Preterm birth is associated with asthma-like symptoms in childhood and possibly in adolescence, but the longer-term risk of asthma is unknown and increasingly relevant as larger numbers of these individuals enter adulthood. Our objective was to evaluate whether those who were born preterm are more likely to be prescribed asthma medications in young adulthood than those who were born term.

PATIENTS AND METHODS

We conducted a national cohort study of all singleton infants born in Sweden from 1973 through 1979 (n = 622 616), followed to ages 25.5 to 35.0 years to determine whether asthma medications were prescribed in 2005-2007. Asthma medication data were obtained from all outpatient and inpatient pharmacies throughout Sweden. To improve the positive predictive value for asthma, the outcome was defined as prescription of (1) both a β-2 agonist inhalant and a glucocorticoid inhalant or (2) a combination inhalant containing a β-2 agonist and other drugs for obstructive airway diseases.

RESULTS

Young adults who were born extremely preterm (23-27 weeks' gestation) were 2.4 times more likely (adjusted 95% CI: 1.41-4.06) to be prescribed asthma medications than those who were born term. No association was found between later preterm birth (28-32 or 33-36 weeks' gestation) and asthma medications in young adulthood.

CONCLUSIONS

This is the first study with sufficient statistical power to evaluate the risk of asthma beyond adolescence in individuals who were born extremely preterm. The results suggest that extreme preterm birth (23-27 weeks' gestation), but not later preterm birth, is associated with an increased risk of asthma at least into young adulthood.

Perinatal and early life risk factors for inflammatory bowel disease

AIM: To investigate associations between perinatal risk factors and subsequent inflammatory bowel disease (IBD) in children and young adults.

METHODS: Record linked abstracts of birth registrations, maternity, day case and inpatient admissions in a defined population of southern England. Investigation of 20 perinatal factors relating to the maternity or the birth: maternal age, Crohn’s disease (CD) or ulcerative colitis (UC) in the mother, maternal social class, marital status, smoking in pregnancy, ABO blood group and rhesus status, pre-eclampsia, parity, the infant’s presentation at birth, caesarean delivery, forceps delivery, sex, number of babies delivered, gestational age, birthweight, head circumference, breastfeeding and Apgar scores at one and five minutes.

RESULTS: Maternity records were present for 180 children who subsequently developed IBD. Univariate analysis showed increased risks of CD among children of mothers with CD (P = 0.011, based on two cases of CD in both mother and child) and children of mothers who smoked during pregnancy. Multivariate analysis confirmed increased risks of CD among children of mothers who smoked (odds ratio = 2.04, 95% CI = 1.06-3.92) and for older mothers aged 35+ years (4.81, 2.32-9.98). Multivariate analysis showed that there were no significant associations between CD and 17 other perinatal risk factors investigated. It also showed that, for UC, there were no significant associations with the perinatal factors studied.

CONCLUSION: This study shows an association between CD in mother and child; and elevated risks of CD in children of older mothers and of mothers who smoked.

Body weight at birth and at age three and respiratory illness in preschool children

OBJECTIVES

The purpose of this study was to examine the associations of current body weight and body mass index (BMI) at age three and birth weight in developing chronic respiratory illness in childhood and identify possible interaction underlying its mechanism.

METHODS

The study was carried out with 422 children who were enrolled in a hospital-based birth cohort. Birth related anthropometric data were collected at birth. At age 3 years, the presence of respiratory symptoms was evaluated by using the Korean version of core questionnaire for wheezing and asthma from the International Study of Asthma and Allergies in Childhood (ISAAC). Physical examination was carried out to measure the child's weight and height.

RESULTS

Children in the lowest birth weight tertile (aOR = 3.97, 95% CI = 0.94-16.68) or highest BMI tertile (aOR = 3.68, 95% CI = 1.24-10.95) at three years of age were at an increased risk of chronic respiratory illness. Children who were initially in the lowest birth weight tertile but now belong in the highest weight tertile had higher risk of chronic respiratory illness compared to those who had remained in the middle tertile (OR=16.35, 95% CI=1.66-160.57).

CONCLUSIONS

Children with lower birth weight or higher BMI were at an increased risk of chronic respiratory illness. In addition, children who were initially in the lowest birth weight tertile but are now in the highest weight tertile had higher risk of chronic respiratory illness compared to those who remained in the middle tertile.

Asthma and allergic diseases in school children from 1992 to 2007 with incidence data

BACKGROUND

Information about change in the prevalence of asthma and allergic diseases and factors related with these diseases would be beneficial in decreasing the burden of these diseases.

OBJECTIVE

To assess (i) change in prevalence of asthma and allergic diseases; (ii) factors associated with asthma and wheeze; and (iii) incidence of asthma and wheeze.

METHODS

A questionnaire was administered to children aged 7-12 years in first five grades in the same primary school in 1992 (n: 1036), 1997 (n: 738), 2002 (n: 621), and 2007 (n: 422) and filled by the parents. A second survey in 2007 (n: 474, in eight grades) was conducted in the same schoolchildren, 6 months apart, to assess the incidence of asthma and wheeze and the associated factors.

RESULTS

Comparison of 1992, 1997, 2002, and 2007 surveys revealed that prevalence of asthma (8.3%, 9.8%, 6.4%, 3.3%, respectively), wheeze (11.9%, 13.3%, 6.4%, 3.1%, respectively), hay fever (15.4%, 14.1%, 7.2%, 3.1%, respectively), and eczema (4.0%, 4.3%, 1.8%, 1.2%, respectively) were significantly lower in 2002 and 2007 compared with that in 1992. Percentage of passive smoking decreased after 1992 (74.0%, 64.0%, 64.1%, and 65.5%, respectively). Incidence of asthma and wheeze in 2007 surveys were 0.9/100 and 1.1/100, respectively. After the adjustment for age and gender, infection in the past, family atopy, and presence of atopic disease (eczema or hay fever) were associated with asthma and wheeze. Maternal smoking and lack of breast feeding were associated with asthma. Male gender, pet ownership in the past, lack of health insurance coverage, snoring, and wood or coal used as fuel were associated with wheeze.

CONCLUSIONS

Decreased prevalence of asthma and allergic diseases in the last 10 years could be related to decreased rate of passive smoking. Lower socioeconomic status and lack of breast feeding could increase the risk of asthma in children.

Projections of the effects of climate change on allergic asthma: the contribution of aerobiology

Climate change is unequivocal and represents a possible threat for patients affected by allergic conditions. It has already had an impact on living organisms, including plants and fungi with current scenarios projecting further effects by the end of the century. Over the last three decades, studies have shown changes in production, dispersion and allergen content of pollen and spores, which may be region- and species-specific. In addition, these changes may have been influenced by urban air pollutants interacting directly with pollen. Data suggest an increasing effect of aeroallergens on allergic patients over this period, which may also imply a greater likelihood of the development of an allergic respiratory disease in sensitized subjects and exacerbation of symptomatic patients. There are a number of limitations that make predictions uncertain, and further and specifically designed studies are needed to clarify current effects and future scenarios. We recommend: More stress on pollen/spore exposure in the diagnosis and treatment guidelines of respiratory and allergic diseases; collection of aerobiological data in a structured way at the European level; creation, promotion and support of multidisciplinary research teams in this area; lobbying the European Union and other funders to finance this research.

Trends of abnormal birthweight among full-term infants in Newfoundland and Labrador

OBJECTIVES

The objective of this study was to investigate whether any observed trends in birthweight are accompanied by changes in maternal sociodemographic characteristics, including age, marital status, and education.

METHODS

We conducted a population-based study of term singletons born in Newfoundland and Labrador, Canada, between 1992 and 2005 (N = 66,638). Large-sample significance tests for two population proportions were used to test whether differences in mean birthweight, the proportion of low and high birthweight infants, and differences in maternal socio-demographic characteristics between 1992-95 and 2002-05 were statistically significant. Chi-square tests were used to test for associations between birthweight group and maternal age, education and marital status. Multivariate logistic regression was used to examine the interaction of these effects across time periods.

RESULTS

Of the 66,638 infants included in the study, 54,256 (81.4%) were born in the normal birthweight range (2500-4000 grams) while 11,305 (17.0%) were high birthweight (> 4000 grams) and 1,077 (1.6%) were low birthweight (< 2500 grams). The rate of low birthweight significantly decreased from 1992 to 1995 compared to the period 2002 to 2005 (1.9% to 1.3%: p < 0.01). The rate of high birthweight significantly increased over the same two time periods (16.2% to 17.5%: p < 0.01). Mean birthweight increased from 3529 grams to 3566 grams (p < 0.01). Compared to women who had babies from 1992 to 1995, women who gave birth from 2002 to 2005 were more likely to be older, have higher levels of education, and never have been married. Birthweight outcomes were significantly associated with mother's age, education and marital status.

CONCLUSION

Changes in maternal demographics are associated with the upward shift in birthweight in Newfoundland and Labrador.

Use and safety of long-acting β2-agonists for pediatric asthma

Asthma guidelines recommend the use of long-acting β2-agonists (LABAs) as the preferred add-on therapy for adults and children over 5 years of age when asthma is inadequately controlled by inhaled corticosteroids alone. It has been suggested that LABA use may be associated with an increased risk of morbidity and mortality; however, this view is controversial since study findings have been inconsistent. While the safety profile of LABA monotherapy has been questioned, the value of concomitant inhaled corticosteroids to eliminate possible risks remains unproven. There is a paucity of efficacy and safety data for LABA use in children, and existing evidence is not sufficiently convincing to demonstrate a clear position for LABAs in the management of childhood asthma. The main aims of this article are to place LABAs in context in the management of childhood asthma and evaluate the current evidence for safety and efficacy.

Examining the association between childhood asthma and parent and grandparent asthma status: implications for practice

Examination of intergenerational asthma beyond maternal asthma has been limited. The association between childhood asthma and intergenerational asthma status among a national cohort of children was examined. The genealogical sample (2552 children) participating in the Child Development Supplement of the Panel Study of Income Dynamics was studied. Multivariate regression was used to determine intergenerational asthma. Children with a parent with asthma were almost twice as likely (odds ratio [OR] = 1.96) to have asthma compared with those without a parent with asthma. Children with a parent and grandparent with asthma were more than 4 times more likely to have asthma compared with those without a parent and grandparent with asthma (OR = 4.27). Children with a grandparent with asthma were more likely to have asthma (OR = 1.52). A family history of asthma was a significant predictor of physician diagnosed asthma in children regardless of race/ethnicity and socioeconomic status. Findings support the collection of family history, including grandparent asthma status.

Influence of maternal and perinatal factors on subsequent hospitalisation for asthma in children: evidence from the Oxford record linkage study

Background

There is much interest in the possibility that perinatal factors may influence the risk of disease in later life. We investigated the influence of maternal and perinatal factors on subsequent hospital admission for asthma in children.

Methods

Analysis of data from the Oxford record linkage study (ORLS) to generate a retrospective cohort of 248 612 records of births between 1970 and 1989, with follow-up to records of subsequent hospital admission for 4 017 children with asthma up to 1999.

Results

Univariate analysis showed significant associations between an increased risk of admission for asthma and later years of birth (reflecting the increase in asthma in the 1970s and 1980s), low social class, asthma in the mother, unmarried mothers, maternal smoking in pregnancy, subsequent births compared with first-born, male sex, low birth weight, short gestational age, caesarean delivery, forceps delivery and not being breastfed. Multivariate analysis, identifying each risk factor that had a significant effect independently of other risk factors, confirmed associations with maternal asthma (odds ratio (OR) 3.1, 95% confidence interval 2.7-3.6), male sex (versus female, 1.8, 1.7-2.0), low birth weight (1000-2999 g versus 3000-3999 g, 1.2, 1.1-1.3), maternal smoking (1.1, 1.0-1.3) and delivery by caesarean section (1.2; 1.0-1.3). In those first admitted with asthma under two years old, there were associations with having siblings (e.g. second child compared with first-born, OR 1.3, 1.0-1.7) and short gestational age (24-37 weeks versus 38-41 weeks, 1.6, 1.2-2.2). Multivariate analysis confined to those admitted with asthma aged six years or more, showed associations with maternal asthma (OR 3.8, 3.1-4.7), age of mother (under 25 versus 25-34 at birth, OR 1.16, 1.03-1.31; over 35 versus 25-34, OR 1.4, 1.1-1.7); high social class was protective (1 and 2, compared with 3, 0.72; 0.63-0.82). Hospital admission for asthma in people aged over six was more common in males than females (1.4; 1.2-1.5); but, by the teenage years, the sex ratio reversed and admission was more common in females than males.

Conclusion

Several maternal characteristics and perinatal factors are associated with an elevated risk of hospital admission for asthma in the child in later life.

Effect of early life exposure to air pollution on development of childhood asthma

BACKGROUND

There is increasing recognition of the importance of early environmental exposures in the development of childhood asthma. Outdoor air pollution is a recognized asthma trigger, but it is unclear whether exposure influences incident disease. We investigated the effect of exposure to ambient air pollution in utero and during the first year of life on risk of subsequent asthma diagnosis in a population-based nested case-control study.

METHODS

We assessed all children born in southwestern British Columbia in 1999 and 2000 (n = 37,401) for incidence of asthma diagnosis up to 34 years of age using outpatient and hospitalization records. Asthma cases were age- and sex-matched to five randomly chosen controls from the eligible cohort. We estimated each individual's exposure to ambient air pollution for the gestational period and first year of life using high-resolution pollution surfaces derived from regulatory monitoring data as well as land use regression models adjusted for temporal variation. We used logistic regression analyses to estimate effects of carbon monoxide, nitric oxide, nitrogen dioxide, particulate matter <or= 10 microm and <or= 2.5 microm in aerodynamic diameter (PM10 and PM2.5), ozone, sulfur dioxide, black carbon, woodsmoke, and proximity to roads and point sources on asthma diagnosis.

RESULTS

A total of 3,482 children (9%) were classified as asthma cases. We observed a statistically significantly increased risk of asthma diagnosis with increased early life exposure to CO, NO, NO2, PM10, SO2, and black carbon and proximity to point sources. Traffic-related pollutants were associated with the highest risks: adjusted odds ratio = 1.08 (95% confidence interval, 1.041.12) for a 10-microg/m3 increase of NO, 1.12 (1.071.17) for a 10-microg/m3 increase in NO2, and 1.10 (1.061.13) for a 100-microg/m3 increase in CO. These data support the hypothesis that early childhood exposure to air pollutants plays a role in development of asthma.

Schizophrenia and the city: A review of literature and prospective study of psychosis and urbanicity in Ireland

Urbanicity has been repeatedly associated with increased incidence of schizophrenia. This article (a) presents results of a prospective study of urbanicity and schizophrenia in Ireland and (b) reviews the literature relating to urbanicity and schizophrenia. We prospectively compared incidence of schizophrenia and other psychoses in urban and rural catchment areas (over 4years and 7years, respectively) using face-to-face, DSM-III-R diagnostic interviews. Incidence of schizophrenia in males was higher in urban compared to rural areas, with an age-adjusted incidence rate ratio (IRR) of 1.92 (1.52-2.44) for males and 1.34 (1.00-1.80) for females. Incidence of affective psychosis was lower in urban compared to rural areas for males (IRR 0.48; 0.34-0.67) and females (IRR 0.60; 0.43-0.83). These findings are consistent with the literature, which provides persuasive evidence that risk for schizophrenia increases with urban birth and/or upbringing, especially among males. Register-based studies support this conclusion more consistently than studies using face-to-face diagnostic interviews, the difference being related to power. The mechanism of association is unclear but may relate to biological or social/environmental factors or both, acting considerably before psychotic symptoms manifest. There is a diversity of potential candidates, including air pollution, cannabis and social exclusion. Urbanicity may have a synergistic effect with genetic vulnerability. Future research is likely to focus on the relationship between urbanicity and neural maldevelopment, the possibility of rural protective factors (e.g. social capital, low social fragmentation), urbanicity in developing countries, cultural variables and geographical location, and associations between urbanicity and other disorders (e.g. affective psychosis).

What is the lifetime risk of physician-diagnosed asthma in Ontario, Canada?

RATIONALE

Asthma is the most common chronic respiratory disease in Canada. The estimates of risk of developing asthma may help researchers and health planners set research agendas, predict the burden of asthma on society, and target the at-risk population for asthma prevention, management, and control.

OBJECTIVES

To estimate the lifetime risk of physician-diagnosed asthma.

METHODS

All individuals aged 0-79 years living in Ontario, Canada on April 1, 1996 who had not been diagnosed with asthma were monitored for 11 years until March 31, 2007. They were censored when they were diagnosed with asthma, turned age 80 years, or died. The lifetime risk (from birth to age 79 yr) of physician-diagnosed asthma was calculated by a modified survival analysis technique. Results were stratified by sex, rurality, and neighborhood income.

MEASUREMENTS AND MAIN RESULTS

Overall, the lifetime risk of physician-diagnosed asthma was 33.9%. Whereas the overall lifetime risk was higher in females (35.0 vs. 32.9%; P < 0.001), the cumulative risk was higher in males in early years. The lifetime risk was higher in individuals living in urban areas (34.5 vs. 30.1%; P < 0.001) or low-income neighborhoods (35.0% in the lowest income quintile vs. 32.2% in the highest; P < 0.001).

CONCLUSIONS

Our estimated overall lifetime risk indicates that one of every three individuals in Ontario, Canada has physician-diagnosed asthma during one's lifetime.

Risk factors and prevalence of asthma in schoolchildren in Castellon (Spain): a cross-sectional study

BACKGROUND

Research on potential risk factors of asthma can enhance our understanding of geographic differences and inform decisions on preventive strategies.

METHODS

In 2002, a cross-sectional population-based study was carried out in the area of Castellon (Spain), following the International Study of Asthma and Allergies in Childhood (ISAAC) Phase III methodology. Asthma symptoms and related risk factor questionnaires were completed by parents of 6-7 year-old schoolchildren. Logistic regression was used in the analysis.

RESULTS

Participation rate was 88 % (4492 of 4872 schoolchildren). Prevalence of wheeze in the past year, asthma ever, and physician-diagnosed asthma were 8 %, 7 % and 6 %, respectively. Risk factors independently associated with all three asthma case definitions were history of bronchitis or pneumonia, allergic rhinitis, family members with atopic disease, and residing in an industrialised area. Risk factors for asthma ever and physician-diagnosed asthma were male sex, atopic eczema and presence of a dog at home; exclusive breast-feeding and the presence of another animal (not a dog or cat) were protective factors. Maternal age was inversely related to physician-diagnosed asthma. Residence in an area of heavy truck traffic and the father smoking at home were associated with asthma ever. Risk factors for wheeze in the past year were low social class, history of sinusitis and the father smoking at home.

CONCLUSIONS

Environmental factors are related to the presence of asthma. Preventive measures should be directed to improving air pollution, promoting breast-feeding and reducing smoking in the home.

Is the association between low birth weight and asthma independent of genetic and shared environmental factors?

Epidemiologic evidence linking birth weight and asthma is inconsistent. The authors examined the association between birth weight and asthma during childhood and adult life in twins. Using prospectively collected data on 21,588 like-sexed Swedish twins of known zygosity born in 1928-1952, they first conducted a cohort study to examine the risk of asthma in relation to birth weight. Next, they conducted nested co-twin control analyses among 643 dizygotic and 365 monozygotic twin pairs discordant for asthma to ascertain whether the association between birth weight and asthma could be confounded by genetic and shared environmental exposures. In the cohort analysis, birth weight of <2,500 g was associated with significantly greater risk of asthma independent of perinatal characteristics and within-twin-pair correlations. In the co-twin control analyses, birth weight of <2,500 g was significantly related to increased risk of asthma among monozygotic twins (relative risk for 2,000 g vs. 2,500 g = 1.58, 95% confidence interval: 1.06, 2.38). A negative association between birth weight and asthma, albeit not statistically significant, was also found among dizygotic twins. In conclusion, there is a negative association between birth weight and asthma in twins that is unlikely to be confounded by genetic or shared environmental factors.

Fungi and pollen exposure in the first months of life and risk of early childhood wheezing

BACKGROUND

Many studies have found that the risk of childhood asthma varies by month of birth, but few have examined ambient aeroallergens as an explanatory factor. A study was undertaken to examine whether birth during seasons of elevated ambient fungal spore or pollen concentrations is associated with risk of early wheezing or blood levels of Th1 and Th2 type cells at 24 months of age.

METHODS

514 children were enrolled before birth and followed to 24 months of age. Early wheezing was determined from medical records, and Th1 and Th2 type cells were measured in peripheral blood using flow cytometry. Ambient aeroallergen concentrations were measured throughout the study period and discrete seasons of high spore and pollen concentrations were defined.

RESULTS

A seasonal pattern was observed, with birth in autumn to winter (the spore season) associated with increased odds of early wheezing (adjusted odds ratio 3.1; 95% confidence interval 1.3 to 7.4). Increasing mean daily concentrations of basidiospores and ascospores in the first 3 months of life were associated with increased odds of wheeze, as were increasing mean daily concentrations of total and specific pollen types. Levels of Th1 cells at age 24 months were positively associated with mean spore concentrations and negatively associated with mean pollen concentrations in the first 3 months of life.

CONCLUSIONS

Children with higher exposure to spores and pollen in the first 3 months of life are at increased risk of early wheezing. This association is independent of other seasonal factors including ambient levels of particulate matter of aerodynamic diameter <or=2.5 microm and lower respiratory infections.

Determinants of the incidence of childhood asthma: a two-stage case-control study

Extensive literature exists on potential risk factors for childhood asthma. To the authors' knowledge, no investigators have yet attempted to disentangle the effects of those determinants within a single study setting. The authors aimed to evaluate the independent effects of 47 potential determinants (from the prenatal, perinatal, and childhood periods) of asthma development in children within the first 10 years of life. From a Canadian birth cohort of 26,265 children (1990-2002), a 2-stage case-control study was conducted. In the first stage, 20 controls per case were selected from 3 administrative databases. In the second stage, selected mothers were mailed questionnaires for assessment of additional determinants. Increased risks of childhood asthma were found for > or =1 previous diagnosis of bronchopulmonary disease and atopic dermatitis in the child, oxygen administration after birth, prescription of antibiotics within the first 6 months of life, male gender, asthma during pregnancy, use of antibiotics during pregnancy, maternal receipt of social aid, paternal asthma, and asthma in siblings. Protective effects included use of intranasal corticosteroids during pregnancy, having a wood-burning fireplace, having pets in the home prior to the index date, breastfeeding, and day-care attendance. This study allowed the authors to identify, within a single setting, the most influential determinants of childhood asthma among 47 predictors assessed for the prenatal, perinatal, and childhood periods.

Prenatal factors and the development of asthma

PURPOSE OF REVIEW

There is increasing evidence that both prenatal and perinatal events influence both allergic diseases and early-life respiratory morbidity.

RECENT FINDINGS

Studies in the last year have suggested that in-utero exposures including tobacco smoke exposure, dietary exposures including vitamin D, and prenatal infection and exposure to microbial products may modulate both atopy and respiratory disease. There have been studies revealing gene x environment interactions between inflammatory pathway genes and in-utero smoke exposure. There have also been studies which have revealed that prenatal exposure to endotoxin may be protective. On the other hand, a recent study also suggested that chorioamnionitis may increase the risk of recurrent wheezing in combination with preterm birth. Finally, two separate large cohort studies evaluated maternal diet in pregnancy and suggested that vitamin D levels may be protective against asthma and wheezing.

SUMMARY

There is epidemiological evidence for multiple prenatal factors impacting early-life respiratory morbidity. The mechanisms of these factors need further investigation and may act via various pathways which include effects on lung development, allergic and nonallergic inflammation, and airway remodeling. It remains to be determined if some of these early-life factors which predispose to wheezing will all translate into increased risk of asthma.

Childhood asthma surveillance using administrative data: consistency between medical billing and hospital discharge diagnoses

BACKGROUND

The absence of ongoing surveillance for childhood asthma in Montreal, Quebec, prompted the present investigation to assess the validity and practicality of administrative databases as a foundation for surveillance.

OBJECTIVE

To explore the consistency between cases of asthma identified through physician billings compared with hospital discharge summaries.

METHODS

Rates of service use for asthma in 1998 among Montreal children aged one, four and eight years were estimated. Correspondence between the two databases (physician billing claims versus medical billing claims) were explored during three different time periods: the first day of hospitalization, during the entire hospital stay, and during the hospital stay plus a one-day margin before admission and after discharge ('hospital stay +/- 1 day').

RESULTS

During 1998, 7.6% of Montreal children consulted a physician for asthma at least once and 0.6% were hospitalized with a principal diagnosis of asthma. There were no contemporaneous physician billings for asthma 'in hospital' during hospital stay +/- 1 day for 22% of hospitalizations in which asthma was the primary diagnosis recorded at discharge. Conversely, among children with a physician billing for asthma 'in hospital', 66% were found to have a contemporaneous in-hospital record of a stay for 'asthma'.

CONCLUSIONS

Both databases of hospital and medical billing claims are useful for estimating rates of hospitalization for asthma in children. The potential for diagnostic imprecision is of concern, especially if capturing the exact number of uses is more important than establishing patterns of use.

Incidence rates of asthma, rhinitis and eczema symptoms and influential factors in young children in Sweden

AIM

To estimate the incidence rates for asthma, rhinitis and eczema symptoms and to investigate the importance of different influential factors for the incidence of these symptoms.

METHODS

The Dampness in Building and Health study commenced in the year 2000 in Värmland, Sweden with a parental questionnaire based on an ISAAC protocol to all children in the age of 1-6 years. Five years later a follow-up questionnaire was sent to the children that were 1-3 years at baseline. In total, 4779 children (response rate = 73%) participated in both surveys and constitute the study population in this cohort study.

RESULTS

The 5-year incidence of doctor-diagnosed asthma was 4.9% (95% CI 4.3-5.3), rhinitis was 5.7% (5.0-6.4) and eczema was 13.4% (12.3-14.5). However, incidence rates strongly depend on the health status of the baseline population. Risk factors for incident asthma were male gender and short period of breast-feeding. Allergic symptoms in parents were also a strong risk factor for incident asthma, as well as for rhinitis and eczema.

CONCLUSION

When comparing incident rates of asthma between different studies it is important to realize that different definitions of the healthy baseline population will give rise to different incident rates.

Higher adiposity in infancy associated with recurrent wheeze in a prospective cohort of children

BACKGROUND

Few prospective data link early childhood adiposity with asthma-related symptoms.

OBJECTIVE

We sought to examine the associations of weight-for-length (WFL) at age 6 months with incidence of wheezing by age 3 years.

METHODS

We studied 932 children in a prospective cohort of children. The main outcome was recurrent wheezing, which was defined as parents' report of wheezing between 2 and 3 years of age plus wheezing in either year 1 or 2 of life. Secondary outcomes included any wheezing from 6 months to 3 years and current asthma. We used multiple logistic regression to examine associations of 6-month WFL z scores with these outcomes.

RESULTS

At 6 months, the infants' mean WFL z score was 0.68 (SD, 0.94; range -2.96 to 3.24). By age 3 years, 14% of children had recurrent wheezing. After adjustment for a variety of potential confounders, we found that each 1-unit increment in 6-month WFL z score was associated with greater odds of recurrent wheezing (odds ratio [OR], 1.46; 95% CI, 1.11-1.91) and any wheezing (OR, 1.23; 95% CI, 1.03-1.48). We observed a weaker association between 6-month WFL z score and current asthma (OR, 1.22; 95% CI, 0.94-1.59).

CONCLUSION

Infants with higher WFL z scores at 6 months of age had a greater risk of recurrent wheezing by age 3 years. It is unclear whether the relationship of infant adiposity and early-life wheeze extends to allergic asthma or wheeze that can persist into later childhood. Our findings suggest that early interventions to prevent excess infant adiposity might help reduce children's risk of asthma-related symptoms.

A cohort study of traffic-related air pollution impacts on birth outcomes

BACKGROUND

Evidence suggests that air pollution exposure adversely affects pregnancy outcomes. Few studies have examined individual-level intraurban exposure contrasts.

OBJECTIVES

We evaluated the impacts of air pollution on small for gestational age (SGA) birth weight, low full-term birth weight (LBW), and preterm birth using spatiotemporal exposure metrics.

METHODS

With linked administrative data, we identified 70,249 singleton births (1999-2002) with complete covariate data (sex, ethnicity, parity, birth month and year, income, education) and maternal residential history in Vancouver, British Columbia, Canada. We estimated residential exposures by month of pregnancy using nearest and inverse-distance weighting (IDW) of study area monitors [carbon monoxide, nitrogen dioxide, nitric oxide, ozone, sulfur dioxide, and particulate matter < 2.5 (PM2.5) or < 10 (PM10) microm in aerodynamic diameter], temporally adjusted land use regression (LUR) models (NO, NO2, PM2.5, black carbon), and proximity to major roads. Using logistic regression, we estimated the risk of mean (entire pregnancy, first and last month of pregnancy, first and last 3 months) air pollution concentrations on SGA (< 10th percentile), term LBW (< 2,500 g), and preterm birth.

RESULTS

Residence within 50 m of highways was associated with a 22% (95% CI, 0.81-1.87) [corrected] increase in LBW. Exposure to all air pollutants except O3 was associated with SGA, with similar odds ratios (ORs) for LUR and monitoring estimates (e.g., LUR: OR = 1.02; 95% CI, 1.00-1.04; IDW: OR = 1.05; 95% CI, 1.03-1.08 per 10-microg/m3 increase in NO). For preterm births, associations were observed with PM2.5 for births < 37 weeks gestation (and for other pollutants at < 30 weeks). No consistent patterns suggested exposure windows of greater relevance.

CONCLUSION

Associations between traffic-related air pollution and birth outcomes were observed in a population-based cohort with relatively low ambient air pollution exposure.

Prematurity as a predictor of childhood asthma among low-income children

PURPOSE

The purpose of this study was to evaluate the association among birth weight, prematurity, and the prevalence of asthma later in childhood and to assess the degree to which this association may differ between black and white children.

METHODS

Michigan Medicaid claims data from 2001 through 2003 were analyzed to determine asthma prevalence for 150,204 children between ages 5 and 18 years. Asthma cases were identified using Healthcare Effectiveness Data and Information Set persistent asthma criteria and included children having claims for any of the following services within a calendar year: at least one inpatient or one emergency department (ED) claim with an asthma primary diagnosis; at least four asthma medication-dispensing events; or at least four outpatient visits with an asthma diagnosis, and at least two asthma medication-dispensing events. Birth weight and gestational age from birth certificate data were matched with Medicaid files to determine size-for-gestational-age criteria.

RESULTS

Overall, 8.3% of children had persistent asthma; black children had slightly higher asthma prevalence (8.6%) than white children (7.8%; odds ratio [OR]=1.11, 95% confidence interval [CI]: 1.07-1.15). Children born very preterm (<or=32 weeks) had higher prevalence of childhood asthma (11.7%) compared with term births (8.0%; OR=1.51, 95% CI: 1.40-1.63). However, no significant differences were observed in odds of asthma between black and white children born very preterm, preterm (33-36 weeks), or small for gestational age (SGA).

CONCLUSIONS

Regardless of race, children born very preterm had an increased risk of childhood asthma. Although overall asthma prevalence is higher among black children enrolled in Medicaid compared with their white counterparts, these differences were attenuated when prematurity or SGA status were taken into account.