Airway hyperresponsiveness and body mass index: the Child Health and Environment Cohort Study in Hesse, Germany

The impact of obesity on immune function in pediatric asthma

PURPOSE OF REVIEW

Pediatric obese asthma is a complex disease that remains poorly understood. The increasing worldwide incidence of both asthma and obesity over the last few decades, their current high prevalence and the challenges in treating obese asthmatic patients all highlight the importance of a better understanding of the pathophysiological mechanisms in obese asthma. While it is well established that patients with obesity are at an increased risk of developing asthma, the mechanisms by which obesity drives the onset of asthma, and modifies existing asthma, remain unclear. Here, we will focus on mechanisms by which obesity alters immune function in asthma.

RECENT FINDINGS

Lung parenchyma has an altered structure in some pediatric obese asthmatics, known as dysanapsis. Central adiposity is linked to reduced pulmonary function and a better predictor of asthma risk in children than BMI. Obesity in young children is associated with an increased risk of developing asthma, as well as early puberty, and hormonal alterations are implicated in obese asthma. Obesity and asthma each yield immunometabolic dysregulation separately and we are learning more about alterations in these pathways in pediatric obese asthma and the potential impact of bariatric surgery on those processes.

SUMMARY

The recent progress in clarifying the connections between childhood obesity and asthma and their combined impacts on immune function moves us closer to the goals of improved understanding of the pathophysiological mechanisms underpinning obese asthma and improved therapeutic target selection. However, this common inflammatory disease remains understudied, especially in children, and much remains to be learned.

Obesity and childhood asthma

PURPOSE OF REVIEW

Asthma is a common chronic disease of the airways characterized by recurrent respiratory symptoms, bronchoreactivity, and airway inflammation. The high toll on quality of life has led to sustained efforts to understand the factors leading to asthma inception and poor disease control. Obesity is another increasingly common pediatric disease, which appears to increase the risk for incident asthma and worsened disease severity. Currently, our understanding of how obesity affects asthma risk and affects its phenotypic characteristics remains incomplete. The current review describes our current understanding of the epidemiology, clinical characteristics, and management considerations of obesity-related asthma in children.

RECENT FINDINGS

The epidemiologic relationship between obesity in children and incident asthma remains confusing despite numerous longitudinal cohort studies, and appears to be influenced by early life exposures, patterns of somatic growth and underlying familial risks of allergic disease. Children with comorbid obesity and asthma demonstrate diverse phenotypic characteristics which are still becoming clear.

SUMMARY

Like any child with asthma, a child with comorbid obesity requires an individualized approach adhering to current best-practice guidelines and an understanding of how obesity and asthma may interact.

Being Overweight or Obese and the Development of Asthma

OBJECTIVES

Adult obesity is linked to asthma cases and is estimated to lead to 250 000 new cases yearly. Similar incidence and attributable risk (AR) estimates have not been developed for children. We sought to describe the relationship between overweight and obesity and incident asthma in childhood and quantify AR statistics in the United States for overweight and obesity on pediatric asthma.

METHODS

The PEDSnet clinical data research network was used to conduct a retrospective cohort study (January 2009-December 2015) to compare asthma incidence among overweight and/or obese versus healthy weight 2- to 17-year-old children. Asthma incidence was defined as ≥2 encounters with a diagnosis of asthma and ≥1 asthma controller prescription. Stricter diagnostic criteria involved confirmation by spirometry. We used multivariable Poisson regression analyses to estimate incident asthma rates and risk ratios and accepted formulas for ARs.

RESULTS

Data from 507 496 children and 19 581 972 encounters were included. The mean participant observation period was 4 years. The adjusted risk for incident asthma was increased among children who were overweight (relative risk [RR]: 1.17; 95% confidence interval [CI]: 1.10-1.25) and obese (RR: 1.26; 95% CI: 1.18-1.34). The adjusted risk for spirometry-confirmed asthma was increased among children with obesity (RR: 1.29; 95% CI: 1.16-1.42). An estimated 23% to 27% of new asthma cases in children with obesity is directly attributable to obesity. In the absence of overweight and obesity, 10% of all cases of asthma would be avoided.

CONCLUSIONS

Obesity is a major preventable risk factor for pediatric asthma.

Overweight in childhood and adolescence: Does it lead to airway hyperresponsiveness in adulthood?

BACKGROUND

Obesity is increasing worldwide among children and adolescents, and has been associated with an increased incidence of asthma. However, the mechanisms underlying this association are incompletely understood.

OBJECTIVE

In this cohort study we aimed to investigate whether being overweight in childhood and adolescence is associated with an increased risk of airway hyperresponsiveness (AHR), a hallmark of asthma, in early adulthood.

METHODS

Of 527 subjects from a random population sample of children and adolescents (7-17 years) examined at baseline, a total of 184 subjects completed the follow-up visit 20 years later and were included in the present analysis. Both visits included assessment of height and weight, case history and spirometry. At both visits, bronchial provocation tests were performed using either histamine (baseline) or methacholine (follow-up). In addition, fractional exhaled nitric oxide (FeNO) was measured at follow-up.

RESULTS

No significant difference in the prevalence of AHR at follow-up was found between subjects who were overweight or obese at baseline visit (n = 26) (pediatric definition, body mass index ≥ 85%percentile) and normal weight subjects (n = 158) (positive bronchial provocation tests: 15.4% vs. 22.2%, respectively, p = 0.35). Likewise, follow-up FeNO levels did not differ significantly between subjects who were lean and those who were overweight or obese at baseline (geometric mean (95% confidence interval [CI]) 15.1 (13.7, 16.6) parts per billion (ppb) versus 13.0 (10.6, 15.9) ppb, p = 0.23).

CONCLUSION

In children and adolescents, being obese or overweight seems not to be associated with an increased risk of AHR or increased FeNO levels in early adulthood.

Weight-for-length, early weight-gain velocity and atopic dermatitis in infancy and at two years of age: a cohort study

Background

Overweight and atopic dermatitis (AD) are major health problems in most industrialised countries, but the relationship between overweight and AD in infants and young children is unclear. We investigated if weight-for-length at birth, in infancy and at two years, as well as early weight-gain velocity, are associated with the development of AD in early life.

Methods

Cohort study of infants (n = 642), all living in south-east Norway, hospitalized with acute bronchiolitis (n = 404) or recruited from the general population (n = 238), examined at mean age 5.1 months (enrolment) and at a two-year follow-up visit (n = 499; 78%) at mean age 24.6 months. Exposures were weight-for-length (g/cm) at birth, enrolment and two-year follow-up, and early weight-gain velocity (gram/month from birth to enrolment). Excessive weight-for-length was defined as weight-for-length >95^th percentile of WHO child-growth standards. Data on weight-for-length at the three time points were obtained for 435, 428 and 473 children. AD was diagnosed according to the Hanifin & Rajka criteria or from a history of physician-diagnosed AD. We performed multivariate analyses with weight-for-length at birth, at enrolment and at the two-year follow-up visit and with early weight gain velocity for the endpoint AD at each visit.

Results

In adjusted analyses, excessive weight-for-length at enrolment was associated with concurrent AD (OR 3.03; 95% CI 1.23–7.50) and with AD at two years (OR 2.40; 1.11–5.17). In infants without AD, weight-for-length at enrolment increased the risk of AD at two years, with OR being 1.02 (95% CI 1.00–1.04) per increased gram/cm. AD at two years was not associated with concurrent excessive weight-for-length, nor was AD at any time associated with weight-for-length at birth or with early weight-gain velocity.

Conclusions

The results suggest that overweight in infancy may contribute to the development of AD in early life, highlighting the need for child health-care professionals to address potential overweight and atopic disease when advising infants’ caregivers.

Trial registration

ClinicalTrials.gov number, NCT00817466, EudraCT number, 2009–012667-34.

Is impaired glucose metabolism the missing piece in the obesity-asthma puzzle?

Obesity is a major risk factor for several conditions including atherosclerotic disease, metabolic syndrome, and upper airway dysfunction. However, the purported link between obesity and asthma has remained more difficult to define, in part due to limitations in past epidemiologic studies and the inherent challenge in accurately defining asthma in children. It is possible that obesity leads to asthma only in the presence of a mediating variable such as an obesity-related conditions such as esophageal reflux or insulin resistance. The article by Karampatakis and colleagues in this week's edition of the journal is important because it addresses the hypothesis that altered glucose metabolism/insulin resistance associates with bronchial hyperresponsiveness (BHR), a central and objectively measured marker of asthma. They studied pre-pubertal children with and without asthma with a range of body mass indices and found for the first time in pre-pubertal asthmatic children that both insulin resistance and impaired glucose tolerance were more closely related to BHR than was obesity. Their work opens the way for directed mechanistic study of the effects of impaired glucose metabolism on airway development during childhood and airway responsiveness, and for the study of insulin sensitizing therapies in children to prevent lower airway disease. Pediatr Pulmonol. 2017;52:147-150. © 2016 Wiley Periodicals, Inc.

Association of obesity and severity of acute asthma exacerbations in Filipino children

BACKGROUND

Increased body mass index (BMI) may be a risk factor for the development and severity of asthma. However, the effect of obesity on asthma exacerbations is unclear.

OBJECTIVE

To examine the association of obesity and the severity of acute asthma exacerbations.

METHODS

A retrospective cohort of children aged 5 to 18 years who were seen in the emergency department and admitted for acute asthma exacerbation from 2009 to 2011 was reviewed. Weight and height data to compute the BMI were taken from the medical record review. The Centers for Disease Control and Prevention BMI-for-age growth charts for boys and girls aged 2 to 20 years were used to classify underweight, normal, overweight, and obese. Severity of asthma exacerbations into mild, moderate, or severe was determined using criteria by the Global Initiative for Asthma 2010. The χ(2) test of association or the Fisher exact probability test for small samples was used to determine the association between nutritional status and severity of asthma exacerbations.

RESULTS

Of the 303 cases reviewed, most were boys with a mean (SD) age of 10 (3.8) years. The prevalence of overweight and obese children admitted for acute asthma exacerbation was 21% and 28%, respectively. No significant difference was found in the severity of asthma exacerbations, with 82.9% of the nonobese group and 86.8% of the overweight-obese group having moderate-to-severe exacerbation (likelihood ratio, 0.879; 95% CI, 0.42-0.41; P = .88).

CONCLUSION

Our findings suggest that the severity of acute asthma exacerbations was not affected by increased BMI.

Racial disparity in the association between body mass index and self-reported asthma in children: a population-based study

OBJECTIVE

To examine the racial disparity in the association between obesity and asthma in US children and adolescents.

METHODS

This study was based on a nationally representative, random-digit-dial sample of US households with children less than 18 years of age from the National Survey of Children's Health in 2011/2012 and 2007. The study sample included 88,668 children ages 10-17 with data on body mass index (BMI), parental reporting of asthma diagnosis, and potential confounders. Multiple logistic regression analysis was performed to estimate the crude and adjusted odds ratios stratified by child race/ethnicity.

RESULTS

The prevalence of overweight was 15.2% and obesity was 14.1%. Self-reported asthma diagnosis was 16.7% in our study sample. Obese children were 51% more likely to have asthma compared to normal weight children after controlling for child's sex, child age, socioeconomic status, environmental tobacco smoke (ETS), and neighborhood conditions. Our study also shows that the strength of this association varied by race/ethnicity after stratification. Being male, being non-Hispanic Black or Multi-racial, below the Federal Poverty Level, ETS and having detracting neighborhood elements were also significantly associated with higher odds of having a self-reported asthma diagnosis.

CONCLUSION

We observed a racial difference in the association between BMI and asthma in US children. Our findings have significant public health implications and may help public health practitioners to target children and adolescents at higher risk of prevention and intervention efforts.

What factors are associated with the prevalence of atopic symptoms amongst adolescents in Greater Manchester?

INTRODUCTION

Atopy commonly manifests itself as atopic diseases (ADs), namely asthma, eczema and hay fever. The prevalence of AD is rising worldwide, and it is widely accepted as a major public health issue, due to the significant burden of AD on health care systems.

METHOD

Data were obtained from the youth survey of the European Urban Health Indicator System 2 project. The study participants were students aged 14-16 years from Greater Manchester. The main outcomes measured were the prevalence of atopic symptoms and the factors associated with the development of atopy.

RESULTS

Of the sample studied, 70% reported having had an AD during their lifetime. The lifetime prevalence of ever having asthma, eczema or hay fever was 33.4%, 28.1% and 49.0%, respectively. Gender, family affluence, body mass index, diet, smoking and worrying were all significantly associated with atopic symptoms. Smoking was the only variable to be significantly associated with all three ADs. Season of birth and pollution were not shown to be associated with atopic symptoms.

CONCLUSION

This study demonstrates that the prevalence of AD in Greater Manchester was high amongst adolescents. Several environmental, demographic and social factors were found to be significantly associated with the development of atopic symptoms. This study provides a baseline for future studies to further investigate the factors that are associated with AD and allow for the implementation of preventative public health policy.

Association of atopic dermatitis with being overweight and obese: a systematic review and metaanalysis

BACKGROUND

Previous studies found conflicting results about whether atopic dermatitis (AD) is associated with overweight/obesity.

OBJECTIVE

We sought to examine the relationship between AD and overweight/obesity by performing a systematic review and metaanalysis.

METHODS

Observational studies of the relationship between AD and overweight/obesity were selected from PubMed, Embase, and the Cochrane Library. The quality of evidence was assessed using the Newcastle-Ottawa Scale. Fixed and random effects metaanalyses were performed to estimate pooled odds ratios (ORs). Sensitivity analyses were performed that compared results by location of study, study quality, and between studies in children and adults.

RESULTS

In total, 30 studies were included for review. Patients who were overweight (Cochrane-Mantel-Haenszel [CMH] OR, 1.27 [95% confidence interval {CI}: 1.19-1.36]; random effects OR, 1.23 [95% CI: 1.11-1.41]), obese (CMH OR, 1.68 [95% CI: 1.54-1.84]; random effects OR, 1.47 [95% CI: 1.21-1.79]), or overweight/obese (CMH OR, 1.42 [95% CI: 1.34-1.50]; random effects OR, 1.31 [95% CI: 1.16-1.48]) had higher odds of AD than normal weight patients. In sensitivity analyses, children who were overweight (random effects OR, 1.24 [95% CI: 1.08-1.43]), obese (random effects OR, 1.44 [95% CI: 1.12-1.86]), or overweight/obese (random effects OR, 1.32 [95% CI: 1.15-1.51]) and adults who were obese (random effects OR, 1.56 [95% CI: 1.24-1.95]) or overweight/obese (random effects OR, 1.29 [95% CI: 1.05-1.59]) had higher odds of AD. The association remained significant in North America and Asia but not Europe.

LIMITATIONS

Most studies were cross-sectional.

CONCLUSIONS

Overweight/obesity in North America and Asia is associated with an increased prevalence of AD.

Obesity can influence children's and adolescents' airway hyperresponsiveness differently

BACKGROUND

Literature is still arguing about a possible relationship between airway hyperresponsiveness (AHR) and body mass index (BMI). This study aimed at evaluating the influence of BMI on AHR and pulmonary function in children and adolescents that performed a methacholine test for suggestive asthma symptoms.

METHODS

799 consecutive children/adolescents (535 M; mean age: 15 ± 3 yrs; median FEV1% predicted: 101.94% [93.46-111.95] and FEV1/FVC predicted: 91.07 [86.17-95.38]), were considered and divided into underweight, normal, overweight and obese. Different AHR levels were considered as moderate/severe (PD20 ≤ 400 μg) and borderline (PD20 > 400 μg).

RESULTS

536 children/adolescents resulted hyperreactive with a median PD20 of 366 μg [IQR:168-1010.5]; 317 patients were affected by moderate/severe AHR, whereas 219 showed borderline hyperresponsiveness. Obese subjects aged > 13 years showed a lower (p = 0.026) median PD20 (187μg [IQR:110-519]) compared to overweight (377 μg [IQR:204-774]) and normal-weight individuals' values (370.5 μg [IQR:189-877]). On the contrary, median PD20 observed in obese children aged ≤ 13 years (761 μg [IQR:731-1212]) was higher (p = 0.052) compared to normal-weight children's PD20 (193 μg [IQR:81-542]) and to obese adolescents' values (aged > 13 years) (p = 0.019). Obesity was a significant AHR risk factor (OR:2.853[1.037-7.855]; p = 0.042) in moderate/severe AHR adolescents. Females showed a higher AHR risk (OR:1.696[1.046-2.751] p = 0.032) compared to males. A significant relationship was found between BMI and functional parameters (FEV1, FVC, FEV1/FVC) only in hyperreactive females.

CONCLUSIONS

Obesity seems to influence AHR negatively in female but not in male adolescents and children. In fact, AHR is higher in obese teenagers, in particular in those with moderate/severe hyperresponsiveness, and may be mediated by obesity-associated changes in baseline lung function.

Obesity and asthma: an association modified by age

BACKGROUND

Some studies indicate some causal relationship between obesity and asthma, while others show inconsistent results. Our objective was to evaluate the prevalence of asthma according to obesity in children.

METHODS

A cross-sectional study, following the ISAAC study methodology, was conducted on two randomly selected groups consisting of 6-7 year-old children (n=7485) and 13-14 year-old adolescents (n=8496). The asthma symptoms and potential risk factors were determined from the questionnaire. Overweight and obesity were defined based on the body mass index. Multiple logistic regression was used to obtain adjusted prevalence odds ratios (OR) and 95% confidence intervals.

RESULTS

Obesity was associated with an increase in wheezing ever (OR: 1.35) and exercise-induced asthma (OR: 1.62) in the 6-7 year-old group. No significant relationship was observed in the adolescent population.

CONCLUSION

Obesity was associated with a higher prevalence of asthma in young children, but not in adolescents.

Associations between airway hyperresponsiveness, obesity and lipoproteins in a longitudinal cohort

BACKGROUND

Epidemiological data have linked obesity with an increased risk of asthma, but the mechanisms responsible for this relationship remain unknown. One possible mechanism, which has received little attention, could be the effect of cholesterol metabolism on airway smooth muscle function. The present study investigated the association between airway hyperresponsiveness (AHR) to methacholine and body mass index (BMI) and plasma lipoproteins [low-density lipoprotein (LDL), high-density lipoprotein (HDL) and total cholesterol].

METHODS

Associations between AHR, BMI and plasma lipoproteins were assessed in a population-based cohort at ages 14 and 20 years.

RESULTS

In unadjusted analyses, higher LDL cholesterol levels at age 14 were associated with AHR at age 20 in both sexes (P < 0.05). HDL, LDL/HDL ratio and total cholesterol were not associated with AHR. In multiple regression analyses adjusted for sex, lung function, smoking and asthma, only higher levels of BMI at age 14 or 20 years were significantly associated with increased AHR at age 20 years, while neither LDL, HDL and LDL/HDL ratio nor total cholesterol were significantly associated with AHR.

CONCLUSION

We confirmed that in teenagers there is a strong association between BMI and AHR to methacholine. This association seems to be independent of the plasma lipoprotein levels at that age.

Childhood body mass index and risk of asthma in adolescence: a systematic review

Asthma and obesity, both of which are considered global health issues, affect approximately 300 million individuals worldwide. The observation that asthma and obesity tend to increase in parallel may indicate a potential link between these two conditions. The aim of this systematic review of the literature was to investigate the relationship between childhood nutritional status and incidence or persistence of asthma during adolescence. The principal eligibility criteria for selection of articles were including longitudinal analysis, and which measured of exposure during childhood or adolescence and outcome during adolescence. The systematic search initially returned 1563 unique articles. After inspection of titles and reading the abstracts of these articles, we chose 27 for full reading. Of these, 10 were selected to be included in the present review. Of the 10 selected studies, eight showed positive associations between overweight/obesity and asthma. Of these, two were independent of sex, three were found only among men and another three only among women. The present study shows strong evidence that, although the role of sex is not clear, obesity precedes, and is associated with, the persistence and intensity of symptoms of asthma.

Body mass index and acute asthma severity among children presenting to the emergency department

To determine the prevalence of obesity among children presenting to the emergency department (ED) with acute asthma, and to examine the relationship between body mass index (BMI) and acute asthma severity in the ED setting. We analyzed data from a multicenter prospective cohort study during 1997-1998; 44 ED in 17 US states and two Canadian provinces enrolled 672 patients, age 5-17, with acute asthma. BMI and Pulmonary Index were collected in the ED. We defined overweight and obesity using age, sex, and race-specific BMI values from national and international databases. The prevalence of obesity was significantly higher among ED patients with acute asthma as compared with children from the general population (23% vs. 9-15%; p < 0.001). Obese children with acute asthma did not differ from their non-obese counterparts, by demographic factors or chronic asthma severity (all p > 0.2). Initial Pulmonary Index was the same across underweight, intermediate, and obese groups (3.7 +/- 2.4, 3.8 +/- 2.2, 3.7 +/- 2.3; p = 0.70). Admission status also did not vary across groups (22%, 22% and 23%; p = 0.98). Stratifying the analysis by age group and sex did not change these results. The prevalence of obesity among children presenting to the ED with acute asthma was significantly higher compared with children from the general population. BMI was not associated with markers of chronic and acute asthma severity. The results of this study support a positive association between obesity and asthma, and suggest that asthma exacerbations among obese children are very similar to those experienced by other children.

Asthma and obesity in childhood: on the road ahead

Epidemiological data show a link between asthma and obesity, suggesting many different mechanisms that may underlie the association. However, diagnosis of asthma is often self-reported by patients or caregivers. Definition of asthma is crucial, particularly in childhood. Obesity can be associated with symptoms commonly attributed to asthma, such as wheezing, dyspnoea and sleep apnoea. Obese subjects are less fit and may have more frequent bouts of breathlessness on exertion accompanied by an exaggerated symptom perception. Therefore, the link between the two diseases should be analysed by focusing not only on reported diagnosis of asthma but also on objective markers that can better characterize the asthma phenotype. These markers should include lung function parameters, bronchial hyper-reactivity, atopic sensitization and indices of lung inflammation. As we look back and move forward, a multidisciplinary approach is increasingly necessary to understand the complexity of obesity and asthma, keeping in mind that diet and exercise could influence both diagnosis and treatment. In the meantime, in clinical settings, physicians should be cautious about diagnosing asthma in obese children on the basis of self-reported symptoms alone and should confirm the diagnosis by using objective measurements and marker evaluations that can better identify asthma phenotype and exclude overdiagnosis.