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Chronic immune diseases are often reported to be on the rise and are speculated to share early life risk factors. Here, we investigated year of birth as a common denominator for time trends using the consistent data source of the Danish National Patient Registry with 35 years nationwide coverage. Observational nationwide birth cohort registry study, where persons born in Denmark since 1953 were investigated for chronic immune diseases per person years at risk. Outcomes were defined by inpatient hospitalizations in pre-chosen age bins by year of birth in 5 year bins. A population of 3.8 million persons born in Denmark since 1953 was investigated for a total sum of 68 million person years in the ages 5–34 years. We found increasing trends by year of birth for juvenile arthritis age 10–14, adult asthma age 20–24, inflammatory bowel diseases age 20–24, and multiple sclerosis age 25–29, whereas type 1 diabetes age 15–19 was declining until birth year mid 1980s followed by a subsequent increase. Childhood asthma age 5–9 inpatient hospitalizations were relatively stable over time. Nationwide introduction of measles, mumps, rubella vaccine in 1987 did not alter the trends. Hospitalization for the chronic immune diseases adult asthma, juvenile arthritis, inflammatory bowel diseases and multiple sclerosis showed a general increasing trend by birth year in recent 35 years while diabetes 1 and childhood asthma seemed stable in this period. These results were not affected by the introduction of vaccinations against the major childhood viral infections.

Asthma and autoimmune disorders might be affected by opposing immune mechanisms, T helper cells type 2 (Th2) and T helper cells type 1 (Th1) immunity, respectively. Knowledge on comorbidity can increase understanding of the underlying etiologies. We aim to examine the association between childhood asthma and subsequent risk of type 1 diabetes (T1D) and inflammatory bowel diseases (IBD) in Danish children. Children of Danish origin born during 1991–1996 were included and childhood asthma, defined as a minimum of two collected prescriptions of inhalation corticosteroids age 5–7 years, was linked to hospitalisations with either T1D or IBD after age 8. Associations between childhood asthma and incidence of T1D and IBD were analysed using sex- and year stratified Cox regression. A total of 366,200 children were included in the study, 4.9% had asthma, which increased the risk of both T1D and IBD, hazard ratios of 1.32 (1.08–1.61) and 1.27 (1.09–1.48). In this large nationwide Danish study, we found that children with asthma have increased risk of developing immune diseases T1D and IBD. This contradicts the Th1 vs Th2 paradigm and points towards shared disease mechanisms and risk factors.

Childhood asthma is consistently reported to have increased in recent decades in most westernized countries, but it is unknown if this increase is similar across severities. We aimed to study the time-trend of acute hospital admission and readmission for asthma of schoolaged children in the recent 35 years in Denmark. We analyzed time-trends in the national incidence rate of hospitalization for acute severe asthma in children aged 5-15 in Denmark during the 35-year period 1977-2012 in the Danish national registry. Only in-patient admissions with a principal diagnosis of asthma (ICD-8: 493** or ICD-10: J45** or J46**) were included. Among children with asthma hospitalizations, we investigated the risk of readmission beyond 1 month of first admission. Admissions were summarized as rates per thousand person years at risk. The overall time-trend is stable with a rate of one admission per year per thousand children at risk and a peryear incidence rate ratio 0.999 [95 % CI 0.997-1.001]. The rate of any readmission decreased from approximately 20 per thousand children in the eighties to less than 10 in the early nineties before stabilizing at around 10 per thousand children from mid-nineties and onwards. During 35 years of nation-wide follow-up, we find a highly stable incidence rate of first hospital admission for acute severe asthma in children. Moreover, rates of readmission halved during the seventies and stabilized in the last twenty years. In conclusion, our data suggest that the reported increase in childhood asthma is mainly due to less severe cases.

During the 2009 H1N1 pandemic the Danish National board of Health carried out massive public hygiene campaigns to limit spread of disease. We aimed to investigate whether this resulted in lower incidences of communicable diseases in the paediatric population. The study compared annual hospitalization rates for childhood infections from 2005 to 2011. Admission rates for infections were higher during the year of the pandemic compared to the rest of the period. There were no indications of a preventive effect by the hygiene campaign on incidence of severe common childhood infections.

Preeclampsia reflects an unusual increase in systemic inflammation during pregnancy. We studied associations between preeclampsia and asthma, allergy, and eczema in Copenhagen Prospective Studies on Asthma in Childhood (COPSAC ) and in national registries. COPSAC is a high-risk birth cohort of 411 Danish children. Asthma, allergy, and eczema were diagnosed prospectively, and lung function measured at age 1 month and 7 years. Sensitization was evaluated at age 6 months, 18 months, 4 years, and 6 years by skin prick tests and IgE measurements. The register-based cohort included 1.7 million children from Danish national registries in the 35-year period 1977-2012. Children born to mothers with preeclampsia were analyzed regarding risk of asthma, allergy, and eczema. In the COPSAC cohort, 5.6% (n = 23) were diagnosed with preeclampsia. Preeclampsia was associated with increased risk of treatment with inhaled corticosteroids at age 7 years (adjusted odds ratio, 4.01 [95% confidence interval (CI), 1.11-14.43]; P = 0.0337), increased bronchial responsiveness to methacholine (adjusted β-coefficient log-μmol, -0.80 [95% CI, -1.55 to -0.06]; P = 0.0348), and allergic rhinitis (adjusted odds ratio, 4.83 [95% CI, 1.58-14.78]; P = 0.0057) in the 7-year-old children. Furthermore, the children had an increased risk of sensitization to both aeroallergens and food allergens, and increased amount of total IgE during childhood. In the registry-based cohort, 3.7% (n = 62,728) were born to mothers with preeclampsia. Preeclampsia was associated with increased risk of asthma, eczema, and aeroallergen and food allergy, especially pronounced after a duration of preeclampsia of 14 days or more. Maternal asthma increased the risk of preeclampsia. Preeclampsia is a shared prenatal risk factor for asthma, eczema, and allergy in childhood pointing toward in utero immune programming of the child.

Klaus Bønnelykke and colleagues identify a common variant in CDHR3 associated with early childhood asthma with severe exacerbations. CDHR3 encodes a cell adhesion protein expressed at high levels in airway epithelium, suggesting a role for altered epithelial integrity in asthma pathogenesis. Asthma exacerbations are among the most frequent causes of hospitalization during childhood, but the underlying mechanisms are poorly understood. We performed a genome-wide association study of a specific asthma phenotype characterized by recurrent, severe exacerbations occurring between 2 and 6 years of age in a total of 1,173 cases and 2,522 controls. Cases were identified from national health registries of hospitalization, and DNA was obtained from the Danish Neonatal Screening Biobank. We identified five loci with genome-wide significant association. Four of these, GSDMB , IL33 , RAD50 and IL1RL1 , were previously reported as asthma susceptibility loci, but the effect sizes for these loci in our cohort were considerably larger than in the previous genome-wide association studies of asthma. We also obtained strong evidence for a new susceptibility gene, CDHR3 (encoding cadherin-related family member 3), which is highly expressed in airway epithelium. These results demonstrate the strength of applying specific phenotyping in the search for asthma susceptibility genes.

AbstractObjectiveTo examine the effect of supplementation with n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) in pregnancy on anthropometry and body composition in offspring.DesignDouble blinded, randomised controlled trial.SettingCopenhagen Prospective Studies on Asthma in Childhood2010 cohort.Participants736 pregnant women and their offspring.Interventionn-3 LCPUFA (fish oil) or control (olive oil) daily from pregnancy week 24 until one week after birth.Main outcome measuresHeight/length, weight, head, and waist measurements and body composition from dual energy x ray absorptiometry (all pre-specified secondary endpoints of the n-3 LCPUFA trial; the primary outcome for the trial was persistent wheeze/asthma).ResultsThe mean body mass index (BMI) z score was increased between age 0 and 6 years in the fish oil supplementation group compared with the control group (0.14 (95% confidence interval 0.04 to 0.23); P=0.006). At 6 years, supplementation was associated with a higher BMI z score (0.19 (0.06 to 0.32); P=0.004), a higher weight/height (3.48 (0.38 to 6.57) g/cm; P=0.03), and a larger waist circumference (0.6 (0.0 to 1.2) cm; P=0.04) but not a higher proportion of obese children, using International Obesity Task Force grades. The dual energy x ray absorptiometry scan at age 6 years showed a higher total mass (395.4 (86.6 to 704.3) g; P=0.01) in the supplementation versus the control group, explained by a higher lean mass (280.7 (98.9 to 462.4) g; P=0.002), a higher bone mineral content (10.3 (2.3 to 18.1) g; P=0.01), and a non-significantly higher fat mass (116.3 (−92.9 to 325.5) g; P=0.28), but no differences were seen in total body fat or lean mass percentage.ConclusionFish oil supplementation from the 24th week of pregnancy led to a higher BMI in the offspring from 0 to 6 years of age but not an increased risk of obesity at age 6. The body composition at age 6 years in children given fish oil supplementation was characterised by a proportional increase in lean, bone, and fat mass suggesting a general growth stimulating effect of n-3 LCPUFA.Trial registrationClinicaltrials.gov NCT00798226

BackgroundInfants and young children might be particularly susceptible to the potential side effects from inhaled corticosteroid (ICS) on height and bone mineral content (BMC), but this has rarely been studied in long-term prospective studies.MethodsChildren from two Copenhagen Prospective Studies on Asthma in Childhood cohorts were included. ICS use was registered prospectively from birth to age 6 and the cumulative dose was calculated. Primary outcomes were height and BMC from dual-energy X-ray absorptiometry (DXA) scans at age 6.ResultsAt age 6, a total of 930 children (84%) from the cohorts had a valid height measurement and 792 (71%) had a DXA scan. 291 children (31%) received a cumulated ICS dose equivalent to or above 10 weeks of standard treatment before age 6. We found an inverse association between ICS use and height, −0.26 cm (95% CI: −0.45 to −0.07) per 1 year standard treatment from 0 to 6 years of age, p=0.006. This effect was mainly driven by children with ongoing treatment between age 5 and 6 years (−0.31 cm (95% CI: −0.52 to −0.1), p=0.004), while there was no significant association in children who stopped treatment at least 1 year before age 6 (−0.09 cm (95% CI: −0.46 to 0.28), p=0.64). There was no association between ICS use and BMC at age 6.ConclusionsICS use in early childhood was associated with reduced height at age 6 years but only in children with continued treatment in the sixth year of life.

BackgroundWe recently conducted a double-blinded randomised controlled trial showing that fish-oil supplementation during pregnancy reduced the risk of persistent wheeze or asthma in the child by 30%. Here, we explore the mechanisms of the intervention.Methods736 pregnant women were given either placebo or n-3 long-chain polyunsaturated fatty acids (LCPUFAs) in the third trimester in a randomised controlled trial. Deep clinical follow-up of the 695 children in the trial was done at 12 visits until age 6 years, including assessment of genotype at the fatty acid desaturase (FADS) locus, plasma fatty acids, airway DNA methylation, gene expression, microbiome and metabolomics.ResultsSupplementation with n-3 LCPUFA reduced the overall risk of non-atopic asthma by 73% at age 6 (relative risk (RR) 0.27 (95% CI 0.06 to 0.85), p=0.042). In contrast, there was no overall effect on asthma with atopic traits (RR 1.42 (95% CI 0.63 to 3.38), p=0.40), but this was significantly modified by maternal FADS genotype and LCPUFA blood levels (interaction p<0.05), and supplementation did reduce the risk of atopic asthma in the subgroup of mothers with FADS risk variants and/or low blood levels of n-3 LCPUFA before the intervention (RR 0.31 (95% CI 0.11 to 0.75), p=0.016). Furthermore, n-3 LCPUFA significantly reduced the number of infections (croup, gastroenteritis, tonsillitis, otitis media and pneumonia) by 16% (incidence rate ratio 0.84 (95% CI 0.74 to 0.96), p=0.009).Conclusionsn-3 LCPUFA supplementation in pregnancy showed protective effects on non-atopic asthma and infections. Protective effects on atopic asthma depended on maternal FADS genotype and n-3 LCPUFA levels. This indicates that the fatty acid pathway is involved in multiple mechanisms affecting the risk of asthma subtypes and infections.Trial registration number NCT00798226.

Asthma with severe exacerbation is the most common cause of hospitalization among young children. We aim to increase the understanding of this clinically important disease entity through a genome-wide association study. The discovery analysis comprises 2866 children experiencing severe asthma exacerbation between ages 2 and 6 years, and 65,415 non-asthmatic controls, and we replicate findings in 918 children from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) birth cohorts. We identify rs281379 near FUT2 / MAMSTR on chromosome 19 as a novel risk locus (OR = 1.18 (95% CI = 1.11–1.25), P discovery  = 2.6 × 10 −9 ) as well as a biologically plausible interaction between functional variants in FUT2 and ABO . We further discover and replicate a potential causal mechanism behind this interaction related to S. pneumoniae respiratory illnesses. These results suggest a novel mechanism of early childhood asthma and demonstrates the importance of phenotype-specificity for discovery of asthma genes and epistasis. Genetic variants discovered through genome-wide association studies for asthma together account for a small portion of the heritability. Here, the authors identify a possible epistatic relationship between coding variants in FUT2 and ABO , especially pronounced in severe and early onset asthma.