Interpregnancy interval might affect the risk of childhood atopy

When a birth cohort grows up: challenges and opportunities in longitudinal developmental origins of health and disease (DOHaD) research

High-quality evidence from prospective longitudinal studies in humans is essential to testing hypotheses related to the developmental origins of health and disease. In this paper, the authors draw upon their own experiences leading birth cohorts with longitudinal follow-up into adulthood to describe specific challenges and lessons learned. Challenges are substantial and grow over time. Long-term funding is essential for study operations and critical to retaining study staff, who develop relationships with participants and hold important institutional knowledge and technical skill sets. To maintain contact, we recommend that cohorts apply multiple strategies for tracking and obtain as much high-quality contact information as possible before the child's 18th birthday. To maximize engagement, we suggest that cohorts offer flexibility in visit timing, length, location, frequency, and type. Data collection may entail multiple modalities, even at a single collection timepoint, including measures that are self-reported, research-measured, and administrative with a mix of remote and in-person collection. Many topics highly relevant for adolescent and young adult health and well-being are considered to be private in nature, and their assessment requires sensitivity. To motivate ongoing participation, cohorts must work to understand participant barriers and motivators, share scientific findings, and provide appropriate compensation for participation. It is essential for cohorts to strive for broad representation including individuals from higher risk populations, not only among the participants but also the staff. Successful longitudinal follow-up of a study population ultimately requires flexibility, adaptability, appropriate incentives, and opportunities for feedback from participants.

Birth order modifies the effect of IL13 gene polymorphisms on serum IgE at age 10 and skin prick test at ages 4, 10 and 18: a prospective birth cohort study

BACKGROUND

Susceptibility to atopy originates from effects of the environment on genes. Birth order has been identified as a risk factor for atopy and evidence for some candidate genes has been accumulated; however no study has yet assessed a birth order-gene interaction.

OBJECTIVE

To investigate the interaction of IL13 polymorphisms with birth order on allergic sensitization at ages 4, 10 and 18 years.

METHODS

Mother-infant dyads were recruited antenatally and followed prospectively to age 18 years. Questionnaire data (at birth, age 4, 10, 18); skin prick test (SPT) at ages 4, 10, 18; total serum IgE and specific inhalant screen at age 10; and genotyping for IL13 were collected. Three SNPs were selected from IL13: rs20541 (exon 4, nonsynonymous SNP), rs1800925 (promoter region) and rs2066960 (intron 1). Analysis included multivariable log-linear regression analyses using repeated measurements to estimate prevalence ratios (PRs).

RESULTS

Of the 1456 participants, birth order information was available for 83.2% (1212/1456); SPT was performed on 67.4% at age 4, 71.2% at age 10 and 58.0% at age 18. The prevalence of atopy (sensitization to one or more food or aeroallergens) increased from 19.7% at age 4, to 26.7% at 10 and 41.1% at age 18. Repeated measurement analysis indicated interaction between rs20541 and birth order on SPT. The stratified analyses demonstrated that the effect of IL13 on SPT was restricted only to first-born children (p = 0.007; adjusted PR = 1.35; 95%CI = 1.09, 1.69). Similar findings were noted for firstborns regarding elevated total serum IgE at age 10 (p = 0.007; PR = 1.73; 1.16, 2.57) and specific inhalant screen (p = 0.034; PR = 1.48; 1.03, 2.13).

CONCLUSIONS

This is the first study to show an interaction between birth order and IL13 polymorphisms on allergic sensitization. Future functional genetic research need to determine whether or not birth order is related to altered expression and methylation of the IL13 gene.

Birth order, atopy, and symptoms of allergy and asthma among inner-city children attending Head Start in New York City

BACKGROUND

In past research, children with older siblings were more likely than others to wheeze at age 2 years, but less likely by age 6 years. Higher infection transmission and a down-regulated allergic immune response as a result of these infections, respectively, were suggested as the causes. However, in a study of children aged 0-3 years in a low-income urban community in New York City, USA, with high asthma prevalence, we observed no birth-order effect.

OBJECTIVE

To evaluate the association between birth order and atopy and respiratory symptoms in 4-year-old children attending Head Start programs in NYC.

METHODS

Respiratory symptoms were assessed by questionnaire for 1005 children (mean age 4.0 years) living in high asthma prevalence neighbourhoods. Serum was collected from a subgroup of the children (n=494) and specific IgE responses to dust mite, cockroach, mouse, and cat allergens were measured.

RESULTS

Prevalence of specific IgE (> or =0.35 IU/mL) did not differ significantly among first (35%), second (35%), and later-born children (28%) (P=0.23). Increasing birth order was associated with increasing prevalence of respiratory symptoms in the prior year, including wheeze (first 20%, second 27%, third or later 35%; P<0.001), being awakened at night by cough (28%, 33%, 38%; P=0.005), emergency department visits (14%, 17%, 21%; P=0.02) and hospitalizations for difficulty breathing (6.1%, 6.6%, 10%; P=0.04). The associations of birth order with respiratory symptoms were statistically significant only for the non-seroatopic children and those without an asthmatic parent.

CONCLUSIONS

Non-seroatopic children with older siblings were more likely than those without older siblings to have respiratory symptoms at age 4 years. Although the stability of these associations over time remains to be determined, the differences in findings between this study and our previous NYC birth cohort study suggest that patterns of asthma development may vary even among low-income populations within the same city.

Pregnancy, but not the allergic status, influences spontaneous and induced interleukin-1beta (IL-1beta), IL-6, IL-10 and IL-12 responses

In this study, we investigated how pregnancy influences cytokine production in response to stimulation of the innate and the adaptive immune system, respectively. Peripheral blood mononuclear cells (PBMCs) from allergic (n = 44) and non-allergic (n = 36) women were collected at three time-points: during the third trimester, at delivery and at a non-pregnant state 2 years after delivery. The production of interleukin-1beta (IL-1beta), IL-6, IL-10 and IL-12 was measured by enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot assay (ELISPOT). The spontaneous cytokine production, and the response following stimulation with agents that primarily activate the adaptive part of the immune system [phytohaemagglutinin (PHA), allergen extracts from cat and birch], or lipopolysaccharide (LPS) that activate innate immunity was measured in vitro. There was a significantly higher spontaneous in vitro production of IL-1beta, IL-6 and IL-10 by PBMCs during pregnancy than 2 years after pregnancy, and this was not affected by the allergic status of the women. Conversely, in PHA-stimulated cell cultures there was a lower production of IL-10 and IL-12 during pregnancy than 2 years after pregnancy. LPS-induced IL-6 levels were significantly lower in PBMCs obtained during pregnancy than at 2 years after pregnancy. In addition, we made the interesting observation that in allergic women total immunoglobulin E (IgE) levels were significantly lower 2 years after pregnancy compared to the levels during pregnancy. Taken together, our results indicate that while atopic allergy in women does not have a substantial effect on cytokine production, pregnancy has an obvious effect on the immune system in terms of cytokine production as well as on the total IgE levels.