Risk factors for asthma at 3.5 and 7 years of age

A novel concept of screening for subgrouping factors for the association between socioeconomic status and respiratory allergies

BACKGROUND

The new subgroup screening tool "subscreen" aims to understand the unclear and complex association between socioeconomic status (SES) and childhood allergy. This software R package has been successfully used in clinical trials but not in large population-based studies.

OBJECTIVE

To screen and identify subgrouping factors explaining their impact on the association between SES and respiratory allergies in childhood and youth.

METHODS

Using the national German childhood and youth survey dataset (KiGGS Wave 2), we included 56 suspected subgrouping factors to investigate the association between SES (low vs. high) and allergic rhinitis and/or asthma in an exploratory manner. The package enabled a comprehensive overview of odds ratios when considering the SES impact per subgroup and analogously all disease proportions per subgroup.

RESULT

Among the 56 candidate factors, striking subgrouping factors were identified; e.g., if mothers were younger and in the low SES group, their children had a higher risk of asthma. In addition children of the teen's age were associated with increased risks in the low SES group. For the crude proportions, factors such as (parental) smoking or having had no "contact with farm animals" were identified as strong risk factors for rhinitis.

SIGNIFICANCE

The "subscreen" package enabled the detection of notable subgroups for further investigations exemplarily for similar epidemiological research questions.

The relationship of domestic pet ownership with the risk of childhood asthma: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The relationship between pet ownership and childhood asthma remains controversial. In recent years, there have been increasing studies with large sample size. Therefore, we conducted this systematic review and meta-analysis to evaluate the relationship between pet ownership and childhood asthma.

METHOD

Relevant research was retrieved from PubMed, Cochrane, EMBASE, and Web of science. The retrieval was as of October 1, 2021. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the included studies. Stata 15.0 was used to conduct the meta-analysis.

RESULTS

A total of 60 studies with large sample size published between 1995 and 2021 were included in this systematic review and meta-analysis, which included 18 cohort studies and 42 case-control studies covering 27 countries and 1,871,295 children. As shown by meta-analysis results, cat ownership (OR = 1.18, 95%CI: 1.05∼1.33) and dog ownership (OR = 1.12, 95%CI: 1.0 0∼1.24) have a significant bearing on the occurrence of childhood asthma. Pet ownership was also positively correlated with the occurrence of severe childhood asthma (OR = 1.15, 95%CI: 1.11∼1.20).

CONCLUSION

Pet ownership, especially cats and dogs, is associated with the occurrence of asthma in children.

Effect of Exposure to Cats and Dogs on the Risk of Asthma and Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Controversies persist regarding whether exposure to cat or dog increases the risk of asthma and allergic rhinitis.

OBJECTIVE

This meta-analysis aimed to assess the associations between exposure to cats or dogs and the development of asthma and allergic rhinitis.

METHODS

A systematic review was performed to identify case-control and cohort studies before May 2019, evaluating the association between exposure to cats and dogs and the risk of asthma and rhinitis. The risk of bias was assessed using the Newcastle-Ottawa Scale. The odds ratios (ORs) and risk ratios (RRs) were pooled for case-control and cohort studies, respectively. Subgroup analyses were performed on prespecified study-level characteristics.

RESULTS

The meta-analysis of 34 cohort studies showed a protective role of exposure to cats [RR: 0.88, 95% confidence interval (CI): 0.77-0.99] or dogs (RR: 0.85, 95% CI: 0.73-0.97) in the development of asthma. The subgroup analysis of birth cohort (RR: 0.74, 95% CI: 0.56-0.93) and children population (RR: 0.83, 95% CI: 0.70-0.96) also suggested a favorable role of exposure to dogs in the development of asthma. Pooled evidence from 13 case-control studies indicated no significant impact of cats (OR: 1.66, 95% CI: 0.39-2.94) and dogs (OR: 1.22, 95% CI: 0.92-1.52) on the development of asthma. A pooled analysis of five cohort studies showed a favorable effect of exposure to cats (RR: 0.60, 95% CI: 0.33-0.86) or dogs (RR: 0.68, 95% CI 0.44-0.90) on the development of allergic rhinitis.

CONCLUSION

The findings indicated a protective effect of exposure to cats and dogs, especially ownership, on the development of asthma and allergic rhinitis.

Assessment of pet exposure by self-report in epidemiological studies of allergy and asthma: a systematic review

OBJECTIVE

In epidemiological studies that aim to investigate the relationship between pet exposure and allergy/asthma, pet exposure is often ascertained by means of a questionnaire, but it is unclear which questionnaire items are used. The objective of this study was to systematically review self-reported pet exposure assessment in questionnaires used in epidemiological studies which explore the associations between pets and allergy/asthma.

METHODS

A systematic literature search was conducted in PubMed and papers were selected according to pre-specified eligibility criteria. The pet exposure questions used were classified within a framework including direct pet contact, indirect pet contact (e.g. through carers or grandparents) and avoidance behaviour. Authors were contacted when the questions used were not reported in detail.

RESULTS

Ninety-six full text papers were systematically reviewed. All studies assessed direct pet contact, but less than half (45%) explicitly assessed whether pets were allowed indoors. The vast majority of studies assessed both pet exposures during the first year of life and after the first year of life. The minority (13%) assessed whether pet(s) were kept at places regularly visited by the child and pet exposure in utero (15%). Even fewer studies assessed indirect contact to pets (n = 8) and avoidance behaviour (n = 10).

CONCLUSIONS

In epidemiological studies, the ascertainment of pet exposure through questionnaires appears to vary greatly. This variation might partly explain the inconsistent and contradictory results of the effects of pet exposure on the development of allergy and asthma.

The case of drug causation of childhood asthma: antibiotics and paracetamol

AIM

The rising prevalence of bronchial asthma has led to world-wide efforts to understand and stem this development. Cross-sectional studies appear to show that early childhood use of antibiotics may be an important contributory factor, with paracetamol as an additional suspected cause. However, mounting evidence, which is reviewed here, points to various confounding factors as the major reasons for these reported associations.

METHODS

PubMed and EMBASE were systematically searched for studies on associations between antibiotics and/or paracetamol with asthma and/or wheezing, published up to November 2012. A total of 64 pertinent studies were identified, 35 focusing on antibiotics, 19 on paracetamol, and ten addressing both antibiotics and paracetamol, bringing the number of relevant datasets to 74.

RESULTS

Numerous studies were cross-sectional and made no adjustment for the indication of antibiotics or paracetamol; consequently, they were unable to dismiss possible confounding by indication. Where such adjustments could be performed (mostly in longitudinal studies), they substantially weakened or entirely eliminated the association with asthma or asthma surrogates present in the unadjusted data.

CONCLUSION

The weight of evidence of the collected studies in our review strongly suggests that the association of antibiotics with childhood asthma reflects various forms of bias, the most prominent of which is confounding by indication. Recent studies and meta-analyses support the same conclusion for paracetamol. Truly indicated antibiotics should not be withheld from infants or young children for fears they might develop asthma. Likewise, there is no sound reason to replace paracetamol as the preferred pain relief and fever medication in this age group.

Pets at birth do not increase allergic disease in at-risk children

BACKGROUND

The literature is contradictory concerning pet exposure and risk of allergic disease in childhood especially among those with a family history of allergy.

OBJECTIVE

To investigate the relationship between cat and dog exposure at birth and allergic outcomes over the first 12 years in a birth cohort selected for familial allergy.

METHODS

A prospective birth cohort of 620 infants with a family history of allergic diseases was recruited. Data on pet keeping, family demographics and cord blood samples were collected at birth. Information on childhood wheeze, eczema and hay fever was collected 18 times in the first 2 years, at 7 years and at 12 years. Skin prick tests were conducted at 2, 7 and 12 years, and in parents. Regression analyses were used to investigate the relevant associations while adjusting for potential confounders.

RESULTS

Exposure to cats or dogs at birth showed a moderate reduction in risk of wheeze (aOR = 0.76; 95% CI 0.53, 1.09) and hay fever (aOR = 0.71; 0.49, 1.02) after 7 years of age. Protective effects were stronger in children of non-sensitized fathers (aOR wheeze 0.55; 0.31, 0.98; aOR hay fever 0.33; 0.15, 0.77 on exposure to cats alone, or cats or dogs at birth). Pet keeping was not related to cord blood IgE or sensitization from 2 to 12 years.

CONCLUSIONS AND CLINICAL RELEVANCE

Pets at birth either decreased or had no effect on allergic disease up to age 12. We found no evidence that exposure to cats or dogs at birth increases the risk of allergic disease in high-risk children.

Antibiotics and asthma medication in a large register-based cohort study - confounding, cause and effect

BACKGROUND

An association between asthma and antibiotic usage has been demonstrated, and the issue of reverse causation and confounding by indication is much debated.

OBJECTIVE

Our aim was to study the association between different classes of antibiotics and prescription of asthma medication in a register-based cohort of all Swedish children, born between July 2005 and June 2009, ever treated with antibiotics.

METHODS

Data on dispensed prescriptions of antibiotics (ATC-codes J01) and asthma medication (ATC-codes R03A-D) were requested from the Prescribed Drug Register. The association between dispensed prescriptions of different classes of antibiotics and asthma medication was analysed with Cox regression and a descriptive sequence symmetry analysis.

RESULTS

In total, 211 192 children had received prescriptions of antibiotics. There was a strong association between prescription of antibiotics and prescription of asthma medication. The hazard ratios (HRs) for asthma medication associated with prescription of amoxicillin, penicillin, cephalosporin and macrolides (Gram-positive infections) were stronger than HRs associated with prescription of sulphonamides, trimethoprim and quinolones (urinary tract infections) and flucloxacillin (skin and soft tissue infections), e.g. first year HR = 2.27 (95% confidence intervals 2.17-2.37) as compared with HR = 1.04 (0.78-1.40). The HR associated with broad spectrum antibiotics was significantly higher than the narrow spectrum.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data suggest that the association between antibiotics and asthma is subject to either reverse causation or confounding by indication due to respiratory tract infections. This implies that careful consideration is required as to whether or not symptoms from the respiratory tract in early childhood should be treated with antibiotics or asthma medication.

Placental chorioamnionitis at term: epidemiology and follow-up in childhood

The objective was to identify histologic chorioamnionitis ("amnionitis") in the placental disc at term and to investigate associations with demographic, lifestyle, and pregnancy factors and with allergic diseases, atopy, and intelligence quotients in childhood. The setting was a population-based case control study of small-for-gestational age infants at term. One thousand and twelve placentas were assessed histologically for amniocentric inflammation of fetal and/or maternal origin using conservative criteria. Data were collected at birth by maternal interview and from medical records. Follow-up data were obtained from 439 and 418 children at 3.5 and 7 years of age, respectively. Amnionitis was identified in 145 placentas (14.3%), with maternal reaction in 97.2% and fetal reaction in 48.3%. In multivariable analysis any amnionitis was significantly associated with a time from membrane rupture to delivery of 6 to 12 hours, but not with times beyond 12 hours, a duration of total labor exceeding 12 hours, ethnicity (incidences ranging from 8.8% in Indians to 23.5% in Chinese), male infant gender, and anaesthesia during labor, and amnionitis was negatively associated with induction of labor. No associations were found with later allergic disease, atopy, or intelligence quotients. This high incidence of histologic amnionitis at term is similar to historical estimates, despite large reductions in time-related risk factors during labor. Significant ethnic variations contribute to the high incidence and are unexplained, but variation in genetic polymorphisms for susceptibility factors is a possibility. "Silent" histologic amnionitis is a frequent cause of fetal immune activation with potential effects in later life.

The role of cats and dogs in asthma and allergy--a systematic review

Studies have reported contradictory effects of cat and dog exposure on allergy, resulting in inconsistent recommendations on animal avoidance. We conducted a systematic review of observational studies published in English from 2000 to January 2009. It shows in this review that the reported exposure-response relationships are contradictory. A total of 17 and 13 birth cohort studies on cat and dog exposure, respectively, are included in the review. Most of the birth cohort studies found that cat or dog exposure in early life had no effect on the development of asthma or wheezing symptoms and dog exposure during infancy was found to protect children from developing sensitization against aeroallergens. A total of 7 and 6 prospective studies in school-age children or adults on cat and dog exposure, respectively, are included in this review and most of these studies suggested an inverse association between cat exposure and asthma and wheezing symptoms. As for cross-sectional studies, 26 and 21 studies on cat and dog exposure, respectively, are included in this review, which cover a broad range of age groups and geographical areas, and reported inconsistent results. The evidence summarised in this systematic review needs to be interpreted with caution, the inconsistent study results may be due to study design, exposure assessment, and avoidance measure. The exposure-response relationships may also alter in geographical areas where the community prevalence of cats and dogs are significantly different. However, as the evidence of the effects of pet keeping on subsequent development of asthma or allergic diseases presented in this review are not overwhelmingly strong, the decision of whether to keep a cat or a dog in the family should be based on arguments other than the concern of developing asthma and allergy.

Cross-sectional survey of risk factors for asthma in 6-7-year-old children in New Zealand: International Study of Asthma and Allergy in Childhood Phase Three

AIM

To identify risk factors for asthma in primary school-aged children in New Zealand.

METHODS

A cross-sectional survey of 10,873 6-7-year-old children in Auckland, Bay of Plenty, Nelson and Christchurch (a response rate of 85.2%). A questionnaire was completed by the parent or care giver.

RESULTS

22.2% of children wheezed in the last 12 months (current wheeze). Maori children were at greater risk of current wheeze compared with European children (adjusted odds ratio (adjOR) = 1.37; 95% confidence interval = 1.18-1.59). Antibiotics and paracetamol used in the first year of life were associated with an increased risk of current wheeze (adjOR = 1.78 (1.56-2.04) and adjOR = 1.31 (1.06-1.61), respectively). Watching television for 5 or more hours per day was associated with an increased risk of current wheeze (adjOR = 1.44 (1.13-1.83)). Milk and egg consumption in the last 12 months was associated with a reduced risk of current wheeze.

CONCLUSIONS

 This study has identified risk factors for asthma in children aged 6-7 years, although causal pathways cannot be established. These associations have important public health implications if causal.

Neutrophilic airway inflammation and association with bacterial lipopolysaccharide in children with asthma and wheezing

Asthma is a leading chronic childhood illness in the US. To gain further insight into the pathophysiology of childhood asthma, we studied markers of airway inflammation and possible triggers such as bacterial lipopolysaccharide (LPS) in 18 children with chronic asthma and persistent wheezing who underwent clinically indicated bronchoscopy and bronchoalveolar lavage (BAL). We predominantly found neutrophilic airway inflammation associated with increased levels of IL-8, metalloproteinase (MMP)-9, tissue inhibitor of metalloproteinase (TIMP-1) and MMP-9/TIMP-1 ratio. A significant correlation was found between levels of LPS in BAL and airway neutrophils in BAL from a subgroup of children who had a tendency of increased levels of MMP-9 and TIMP-1, suggesting that increased LPS levels in BAL may contribute to chronic airway inflammation and early remodeling. Our data highlight the importance of defining chronic triggers of early airway inflammation in children and characterizing their inflammation, considering the use of bronchoscopy and BAL. Increased knowledge of airway inflammation in children may help prevent a more severe asthma phenotype and lead to environmental control measures and new treatment strategies to intervene against the establishment of irreversible inflammation.