Establishing a birth cohort to investigate the course and aetiology of asthma and allergies across three generations - rationale, design, and methods of the ACROSSOLAR study

Epigenetics, hypersensibility and asthma: what do we know so far?

In this review, we describe recent advances in understanding the relationship between epigenetic changes, especially DNA methylation (DNAm), with hypersensitivity and respiratory disorders such as asthma in childhood. It is clearly described that epigenetic mechanisms can induce short to long-term changes in cells, tissues, and organs. Through the growing number of studies on the Origins of Health Development and Diseases, more and more data exist on how environmental and genomic aspects in early life can induce allergies and asthma. The lack of biomarkers, standardized assays, and access to more accessible tools for data collection and analysis are still a challenge for future studies. Through this review, the authors draw a panorama with the available information that can assist in the establishment of an epigenetic approach for the risk analysis of these pathologies.

Parental occupational exposures prior to conception and offspring wheeze and eczema during first year of life

PURPOSE

Parental exposures prior to conception might influence asthma and allergy risk in offspring. As occupational exposures are established risk factors for asthma and allergies, we investigated if parental occupational exposures prior to conception cause wheeze and eczema in offspring during the first year of life.

METHODS

We analysed data of 436 families from an offspring cohort based on a follow-up study of German participants of the International Study of Asthma and Allergies in Childhood (ISAAC). Offspring cohort data was collected between 2009 and 2019. Occupational exposures were based on participants' work histories and measured by a Job-Exposure-Matrix. We used Bayesian logistic regression models for analysis. Inference and confounder selection were based on directed acyclic graphs.

RESULTS

In mothers, for both allergic and irritative occupational exposures prior to conception suggestive effects on offspring eczema during the first year of life were found (allergens: odds ratio (OR) 1.22, 95% compatibility interval (CI) 0.92-1.57; irritants: OR 1.36, 95% CI 0.99-1.77), while no relation with wheeze was suggested.

CONCLUSIONS

Our results suggest that reduction of asthma-related occupational exposures might not only reduce the burden of disease for occupationally induced or aggravated asthma and allergies in employees but also in their children.

The role of epigenetics in multi-generational transmission of asthma: An NIAID workshop report-based narrative review

There is mounting evidence that environmental exposures can result in effects on health that can be transmitted across generations, without the need for a direct exposure to the original factor, for example, the effect of grandparental smoking on grandchildren. Hence, an individual's health should be investigated with the knowledge of cross-generational influences. Epigenetic factors are molecular factors or processes that regulate genome activity and may impact cross-generational effects. Epigenetic transgenerational inheritance has been demonstrated in plants and animals, but the presence and extent of this process in humans are currently being investigated. Experimental data in animals support transmission of asthma risk across generations from a single exposure to the deleterious factor and suggest that the nature of this transmission is in part due to changes in DNA methylation, the most studied epigenetic process. The association of father's prepuberty exposure with offspring risk of asthma and lung function deficit may also be mediated by epigenetic processes. Multi-generational birth cohorts are ideal to investigate the presence and impact of transfer of disease susceptibility across generations and underlying mechanisms. However, multi-generational studies require recruitment and assessment of participants over several decades. Investigation of adult multi-generation cohorts is less resource intensive but run the risk of recall bias. Statistical analysis is challenging given varying degrees of longitudinal and hierarchical data but path analyses, structural equation modelling and multilevel modelling can be employed, and directed networks addressing longitudinal effects deserve exploration as an effort to study causal pathways.

The First 1000 Days of Life Factors Associated with "Childhood Asthma Symptoms": Brisa Cohort, Brazil

This prospective study used data from the BRISA Cohort, São Luís, Brazil (n = 1140) and analyzed associations between environmental factors up to the first 1000 days of life and “Childhood Asthma Symptoms”. “Childhood Asthma Symptoms” was a latent variable based on the number of wheezing episodes, emergency care visit due to wheezing, diagnosis of asthma and diagnosis of rhinitis. A theoretical model that included prenatal factors (socioeconomic status, pregestational body mass index-BMI, soft drink and junk food consumption), birth factors (gestational age, smoking and diseases during pregnancy, birth weight and type of delivery), first year of life factors (breastfeeding, environmental aeroallergens and respiratory diseases) and BMI z-score in the second year of life, was analyzed by structural equation modeling. High pregestational BMI, high soft drink consumption, cesarean section without labor, chill in the first three months of life, carpeted floor and child’s exposure to tobacco were associated with higher values of “Childhood Asthma Symptoms”. In contrast, high birth weight, breastfeeding and infant’s age were associated with lower values of “Childhood Asthma Symptoms”. These findings support the hypothesis that environmental factors that are present before conception and up to the first 1000 days of life are associated with asthma.

Multigenerational cohorts in patients with asthma and allergy

Recent observations that disease risk can be transmitted across generations without the need for direct exposure of the child to the index environmental insult has sparked interest in transgenerational inheritance. Epigenetics describes processes that modify gene expression without a change in the nucleotide sequence. Epigenetic processes can be induced in response to environmental exposures, can influence disease risk, and might explain these multigenerational effects. In experimental models a number of epigenetic mechanisms have been identified that could mediate vertical transmission of epigenetic inheritance. However, relevance of these findings to human disease is not yet clear. An alternative model is one in which transgenerational inheritance of disease risk requires the presence of exposure-related diseases in the mother during pregnancy (termed induced epigenetic transmission model). A number of cross-sectional studies have investigated multigenerational effects in allergy and asthma. However, given the early-life origins of asthma and allergy, birth cohort studies are ideal to investigate the effect of genetic predisposition, epigenetics, and environmental exposures, avoiding pitfalls, such as recall bias and confounding by ongoing exposures, disease, and treatment. The well-characterized 3 generations of the Isle of Wight cohort include 2 consecutive birth cohorts, providing longitudinal data that can be studied for epigenetic transfer of information, such as the effect of grand parental smoking or exposure to other toxic compounds. Further large multigenerational birth cohorts are needed to establish the clinical relevance of this phenomenon and differentiate between vertical and induced transmission models, which might influence future preventive strategies.

Association of household cleaning agents and disinfectants with asthma in young German adults

OBJECTIVES

We scrutinised the association of private use of household sprays and disinfectants with asthma incidence in young adults in the transition from school to working life.

METHODS

Between 2007 and 2009,2051 young adults aged 19-24 years living in two major German cities took part in the Study on Occupational Allergy Risks II. Self-reported exposure to household sprays and disinfectants was characterised according to a composite score for frequency of use as no use (score=0), low use (score between 1 and the median), medium use (score between the median and the 90th percentile) and high use (score above the 90th percentile). Two outcome variables (current asthma and current wheezing) with four mutually exclusive categories (never, incident, persistent and remittent) were used for the risk analyses. Multinomial logistic regression models examined the association between the frequency of using household sprays and disinfectants with asthma and wheezing adjusting for potential confounders.

RESULTS

Compared with no use, high use of disinfectants was associated with a more than twofold increased odds of incident asthma (OR 2.79, 95% CI 1.14 to 6.83). In addition, low/medium use of disinfectants was associated with remittent asthma (OR 2.39, 95% CI 1.29 to 4.47). The evidence for an association between high usage of household sprays and asthma incidence was weak (OR 2.79, 95% CI 0.84 to 9.20).

CONCLUSION

Our results support the hypothesis of an association between the use of cleaning products and elevated risks for asthma and wheezing in young adults at the start of working life.

Extensively hydrolyzed casein formula containing Lactobacillus rhamnosus GG reduces the occurrence of other allergic manifestations in children with cow's milk allergy: 3-year randomized controlled trial

BACKGROUND

Children with cow's milk allergy (CMA) have an increased risk of other allergic manifestations (AMs).

OBJECTIVE

We performed a parallel-arm randomized controlled trial to test whether administration of an extensively hydrolyzed casein formula (EHCF) containing the probiotic Lactobacillus rhamnosus GG (LGG) can reduce the occurrence of other AMs in children with CMA.

METHODS

Children with IgE-mediated CMA were randomly allocated to the EHCF or EHCF+LGG groups and followed for 36 months. The main outcome was occurrence of at least 1 AM (eczema, urticaria, asthma, and rhinoconjunctivitis). The secondary outcome was tolerance acquisition, which was defined as the negativization of a double-blind food challenge results at 12, 24, and 36 months. AMs were diagnosed according to standardized criteria. Tolerance acquisition was evaluated every 12 months.

RESULTS

A total of 220 children (147 boys [67%]) with a median age of 5.0 months (interquartile range, 3.0-8.0 months) were randomized; 110 children were placed in the EHCF group, and 110 children were placed in the EHCF+LGG group. In the complete case analysis the absolute risk difference for the occurrence of at least 1 AM over 36 months was -0.23 (95% CI, -0.36 to -0.10; P < .001), and the absolute risk difference for the acquisition of cow's milk tolerance was 0.20 (95% CI, 0.05-0.35; P < .01) at 12 months, 0.24 (95% CI, 0.08-0.41; P < .01) at 24 months, and 0.27 (95% CI, 0.11-0.43; P < .001) at 36 months. In the sensitivity analysis the effect size of the main outcome was virtually unchanged when the occurrence of AMs was assigned to all 27 missing children.

CONCLUSIONS

EHCF+LGG reduces the incidence of other AMs and hastens the development of oral tolerance in children with IgE-mediated CMA.