Effect of increased body mass index on asthma risk, impairment and response to asthma controller therapy in African Americans

Obesity and Asthma

Obesity is a major risk factor for the development of asthma, and the prevalence of obesity is higher in people with asthma than in the general population. Obese people often have severe asthma-recent studies in the United States suggest that 60% of adults with severe asthma are obese. Multiple mechanisms link obesity and asthma, which are discussed in this article, and these pathways contribute to different phenotypes of asthma among people with obesity. From a practical aspect, changes in physiology and immune markers affect diagnosis and monitoring of disease activity in people with asthma and obesity. Obesity also affects response to asthma medications and is associated with an increased risk of co-morbidities such as gastroesophageal reflux disease, depression, and obstructive sleep apnea, all of which may affect asthma control. Obese people may be at elevated risk of exacerbations related to increased risk of severe disease in response to viral infections. Interventions that target improved dietary quality, exercise, and weight loss are likely to be particularly helpful for this patient population.

T2-"Low" Asthma: Overview and Management Strategies

Although the term "asthma" has been applied to all patients with airway lability and variable chest symptoms for centuries, phenotypes of asthma with distinct clinical and molecular features that may warrant different treatment approaches are well recognized. Patients with type 2 (T2)-"high" asthma are characterized by upregulation of T2 immune pathways (ie, IL-4 and IL-13 gene sets) and eosinophilic airway inflammation, whereas these features are absent in patients with T2-"low" asthma and may contribute to poor responsiveness to corticosteroid treatment. This review details definitions and clinical features of T2-"low" asthma, potential mechanisms and metabolic aspects, pediatric considerations, and potential treatment approaches. Priority research questions for T2-"low" asthma are also discussed.

Asthma medication use in obese and healthy weight asthma: systematic review/meta-analysis

BACKGROUND

Obesity is a common comorbidity in asthma and associated with poorer asthma control, more frequent/severe exacerbations, and reduced response to asthma pharmacotherapy.

OBJECTIVE

This review aims to compare use of all classes of asthma medications in obese (body mass index (BMI) ≤30 kg·m^-2) versus healthy-weight (BMI <25 kg·m^-2) subjects with asthma.

DESIGN

Databases including CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane, Embase and MEDLINE were searched up to July 2019 for English-language studies that recorded medication use or dose in obese and healthy-weight adults with asthma. A critical appraisal checklist was utilised for scrutinising methodological quality of eligible studies. Meta-analysis was performed and heterogeneity was examined with the use of the Chi-squared test. This review was conducted based on a published protocol (www.crd.york.ac.uk/PROSPERO CRD42020148671).

RESULTS

Meta-analysis showed that obese subjects are more likely to use asthma medications, including short-acting β₂-agonists (OR 1.75, 95% CI 1.17-2.60; p=0.006, I²=41%) and maintenance oral corticosteroids (OR 1.86, 95% CI 1.49-2.31; p<0.001, I²=0%) compared to healthy-weight subjects. Inhaled corticosteroid (ICS) dose (µg·day^-1) was significantly higher in obese subjects (mean difference 208.14, 95% CI 107.01-309.27; p<0.001, I²=74%). Forced expiratory volume in 1 s (FEV₁) % predicted was significantly lower in obese subjects (mean difference -5.32%, 95% CI -6.75--3.89; p<0.001, I²=42%); however, no significant differences were observed in FEV₁/forced vital capacity (FVC) ratio between groups.

CONCLUSIONS

We found that obese subjects with asthma have higher use of all included asthma medication classes and higher ICS doses than healthy-weight asthma subjects, despite lower FEV₁ and a similar FEV₁/FVC %. A better understanding of the factors driving increased medication use is required to improve outcomes in this subgroup of asthmatics.

Effect of Obesity on Asthma Severity in Urban School Children of Kanpur, India: An Analytical Cross-Sectional Study

The prevalence of both Obesity and Asthma is increasing worldwide. Various epidemiological data has linked obesity with the development and severity of asthma in children. The aim of this study was to assess if any relationship exists between obesity and asthma in children. The study population included school children aged 5 to 18 years. A total of 320 asthma cases and 300 controls were included in our study. Association analysis of obesity and asthma based on epidemiological basis was measured. Out of 320 cases, 61 children were found to have moderate persistent asthma. Out of 61 moderate persistent asthma cases, 50 children were selected randomly and divided into two groups. Group I included 25 obese moderate persistent asthmatics and Group II included 25 non-obese moderate persistent asthmatics. Forced expiratory volume in one second (FEV₁), Forced vital capacity (FVC), Forced expiratory flow (FEF_25-75%), Peak expiratory flow (PEF) were measured with spirometry and Peak expiratory flow meter. Statistical analysis was done by Odds ratio and p value. Out of 320 cases, 97 were obese and 223 were non-obese. Out of 300 controls, 46 were obese and 254 were non-obese. Exposure rate for cases and controls were 30.31% and 15.33% respectively. Odds ratio was 2.40. χ² value was 19.56 with p value < 0.05.FEV₁, FVC, FEF_{25-75%, PEF} for Group-1 were 66.3 ± 9.9, 63.5 ± 4.2, 54.2 ± 5.7, 67.4 ± 8.4 respectively and FEV₁, FVC, FEF_25-75%, PEF for Group-2 were 74.07 ± 3.5, 77.4 ± 7.2, 60.1 ± 2.1, 71.6 ± 2.4 respectively and p values were < 0.001, < 0.001, < 0.001, < 0.05 respectively which is statistically significant. Children who are obese are more likely to develop severe asthma than those who were not obese.

[Asthma and obesity in adults]

Asthma is a chronic inflammatory airway disorder characterized by a multitude of phenotypes. Epidemiological studies show an increase in asthma prevalence in obese patients regardless of age. The association of asthma and obesity is now considered as a phenotype with its own clinical, biological and functional characteristics. Regarding the pathophysiology of asthma and obesity, numerous factors such as nutrition, genetic predisposition, microbiome, ventilatory mechanics and the role of adipose tissue have been identified to explain the heterogeneous characteristics of patients with asthma and obesity. In adult patients with asthma and obesity, respiratory symptoms are particularly prominent and atopy and eosinophilic inflammation is uncommon compared to normal weight asthma patients. Obese asthma patients experience more hospitalizations and use more rescue medications than normal weight asthmatics. Management of asthma in obese patients is complex because these patients have less response to the usual anti-asthmatic treatments. Weight loss through caloric restriction combined with exercise is the main intervention to obtain improvement of asthma outcomes. Bariatric surgery is an invasive procedure with interesting results.

Drug Dose Selection in Pediatric Obesity: Available Information for the Most Commonly Prescribed Drugs to Children

Obesity rates continue to rise in children, and little guidance exists regarding the need for adjustment away from total body weight-based doses for those prescribing drugs to this population of children. A majority of drugs prescribed to children with obesity result in either sub-therapeutic or supra-therapeutic concentrations, placing these children at risk for treatment failure and drug toxicities. In this review, we highlight available obesity-specific pharmacokinetic and dosing information for the most frequently prescribed drugs to children in the inpatient and outpatient clinical settings. We also comment on available dosing recommendations for drugs prescribed to treat common pediatric obesity-related comorbidities. This review highlights that there is no safe or proven 'rule of thumb,' for dosing drugs for children with obesity, and a striking lack of pharmacokinetic data to support the creation of dosing guidelines for children with obesity for the most commonly prescribed drugs. It is important that those prescribing for children with obesity are aware of these gaps in knowledge and of potential drug treatment failure or adverse events related to drug toxicity as a result of these knowledge gaps. Until more data are available, we recommend close monitoring of drug response and adverse events in children with obesity receiving commonly prescribed drugs.

Influence of weight status in the response to Step-2 maintenance therapies in children with asthma

Introduction

Overweight children with asthma may display impaired response to inhaled corticosteroids (ICS), possibly due to non-eosinophilic inflammation or weight-related lung compression; these mechanisms may differentially affect response to ICS and leukotriene receptor antagonists (LTRAs). We assessed whether weight status modified the response to low-dose ICS and LTRA Step-2 monotherapy.

Methods

A historical cohort study from clinical data linked to administrative databases was conducted among children aged 2–18 years with specialist-diagnosed asthma who were initiating or continuing a Step-2 monotherapy from 2000 to 2007 at the Montreal Children’s Hospital Asthma Centre. The outcome was time-to-management failure defined as any step-up in therapy, acute care visit, hospitalisation or oral corticosteroids for asthma, whichever occurred first. The independent and joint effects of weight status (body mass index [BMI] percentile) and time-varying treatment on time-to-management failure were estimated with marginal structural Cox models. The likelihood ratio test (LRT) and relative excess risk due to interaction (RERI) were computed to assess treatment effect modification by weight status on the multiplicative and additive scales.

Results

Of the 433 and 85 visits with a low-dose ICS and LTRA prescription, respectively, 388 management failures occurred over 14 529 visit-weeks of follow-up. Children using LTRA compared with low-dose ICS tended to have an overall higher risk of early management failure (HR 1.52; 95% CI 0.72 to 3.22). Irrespective of treatment, the hazard of management failure increased by 5% (HR 1.05; 95% CI 1.01 to 1.10) for every 10-unit increase in BMI percentile. An additional hazard reduction of 17% (HR 0.83; 95% CI 0.70 to 0.99) was observed for every 10-unit increase in BMI percentile among LTRA users, but not for ICS (HR 0.95; 95% CI 0.86 to 1.04). The LRT indicated a departure from exact multiplicativity (p<0.0001), and the RERIs for ICS and LTRA were −0.05 (95% CI −0.14 to 0.05) and −0.52 (95% CI −1.76 to 0.71).

Conclusions

Weight status was associated with earlier time-to-management failure in children prescribed Step-2 therapy. This hypothesis-generating study suggests that LTRA response increases in children with higher BMI percentiles, although further research is warranted to confirm findings.

Impact of Obesity on Asthma Morbidity During a Hospitalization

BACKGROUND

Asthma and obesity are 2 common pediatric problems. Obesity is a known risk factor for asthma, and obese children with asthma have higher disease burden. However, little is known on how obesity in urban minority children, mainly Hispanic and African American children, impacts morbidity during pediatric asthma hospitalizations.

METHODS

A retrospective chart review was conducted on children and adolescents age 2 to 18 years hospitalized at the Children's Hospital at Montefiore for an acute asthma exacerbation. We elucidated the association of overweight or obese status with severity of the exacerbation, quantified by length of stay (LOS) and need for intensive care management. Multivariate analysis was conducted to identify independent predictors of LOS.

RESULTS

A total of 975 children met the inclusion criteria, of whom 55% were normal weight and 45% were overweight or obese. Sixty percent were Hispanic, and 37% were African American. The overall average LOS was 2.57 days (range: 0.67-12.92). Overweight or obese status was associated with a higher asthma severity at baseline (P = .021). Overweight or obese children had a longer average LOS compared with normal weight children (2.75 vs 2.39 days; P < .01) with more PICU stays (P = .006), even after adjustment for higher baseline asthma severity. The severity of the exacerbation did not differ by ethnicity.

CONCLUSIONS

Obesity in children hospitalized for asthma is associated with more severe asthma exacerbations, longer LOS, and increased use of PICU level care, independent of their higher baseline disease severity and ethnicity.

The asthma-obesity relationship: underlying mechanisms and treatment implications

PURPOSE OF REVIEW

Obesity is a worldwide epidemic with a prevalence that has tripled in the last two decades. Worldwide, more than 1.5 billion adults are overweight and more than 500 million obese. Obesity has been suggested to be a risk factor for the development of more difficult-to-control asthma. Although the mechanisms underlying the asthma-obesity relationship are not fully understood, several possible explanations have been put forward. These will be reviewed in this manuscript as well as the implications for the treatment of overweight and obese asthma patients.

RECENT FINDINGS

Insulin resistance is a possible factor contributing to the asthma-obesity relationship and the effect is independent of other components of the metabolic syndrome such as hypertriglyceridemia, hypertension, hyperglycemia, and systemic inflammation. Obesity has important effects on airway geometry, by especially reducing expiratory reserve volume causing obese asthmatics to breathe at low lung volumes. Furthermore, obesity affects the type of inflammation in asthma and is associated with reduced inhaled corticosteroids treatment responsiveness.

SUMMARY

Obesity induces the development of asthma with a difficult-to-control phenotype. Treatment targeting insulin resistance may be beneficial in obese asthma patients, especially when they have concomitant diabetes. Systemic corticosteroids should be avoided as much as possible as they are not very effective in obese asthma and associated with side-effects like diabetes, weight gain, and osteoporosis.

Effect of an Outpatient Pulmonary Rehabilitation Program on Exercise Tolerance and Asthma Control in Obese Asthma Patients

PURPOSE

To compare the effects of an outpatient pulmonary rehabilitation (PR) program on exercise tolerance and asthma control in obese and nonobese patients with asthma.

METHODS

Nonobese (body mass index [BMI] <30 kg/m) and obese (BMI ≥ 30 kg/m) patients with asthma who participated in a local multidisciplinary 12-week PR program were analyzed retrospectively. Effects of PR were assessed by changes in 6-minute walking distance (6MWD) and Asthma Control Questionnaire (ACQ).

RESULTS

A total of 138 asthma patients were included: 53 (38.4%) obese and 85 (61.6%) nonobese. At baseline, obese patients with asthma had a lower level of exercise tolerance reflected by a lower 6MWD (525 m vs 621 m; P < .001). After PR, the 6MWD improved significantly in both groups (≥50 m in nonobese vs ≥45 m in obese; P < .001 in both groups). The improvement in 6MWD was clinically relevant in 71% of the nonobese and 60% of the obese patients. These patients had lower 6MWD (P = .024), higher usage of long-acting β-agonist (P = .034) and oral corticosteroids (P = .033). Asthma control also improved in both groups (ΔACQ -0.3 in nonobese vs ΔACQ -0.4 in obese; P = .021 and P = .019, respectively). Clinically relevant improvement was achieved by 46.5% of nonobese and 51.9% of obese patients with asthma. The improvements between the groups were not statistically different.

CONCLUSIONS

A standardized PR program is feasible in obese patients with asthma and they benefit as much as nonobese patients with asthma. However, there are still a large number of patients who show no clinically significant improvement. Patients with more severe asthma seem to benefit the most from PR.

Overweight/obesity status in preschool children associates with worse asthma but robust improvement on inhaled corticosteroids

BACKGROUND

Overweight/obesity (OW) is linked to worse asthma and poorer inhaled corticosteroid (ICS) response in older children and adults.

OBJECTIVE

We sought to describe the relationships between OW and asthma severity and response to ICS in preschool children.

METHODS

This post hoc study of 3 large multicenter trials involving 2- to 5-year-old children compared annualized asthma symptom days and exacerbations among normal weight (NW) (body mass index: 10th-84th percentiles) versus OW (body mass index: ≥85th percentile) participants. Participants had been randomized to daily ICS, intermittent ICS, or daily placebo. Simple and multivariable linear regression was used to compare body mass index groups.

RESULTS

Within the group not treated with a daily controller, OW children had more asthma symptom days (90.7 vs 53.2, P = .020) and exacerbations (1.4 vs 0.8, P = .009) thanNW children did. Within the ICS-treated groups, OW and NW children had similar asthma symptom days (daily ICS: 47.2 vs 44.0 days, P = .44; short-term ICS: 61.8 vs 52.9 days, P = .46; as-needed ICS: 53.3 vs 47.3 days, P = .53), and similar exacerbations (daily ICS: 0.6 vs 0.8, P = .10; short-term ICS: 1.1 vs 0.8 days, P = .25; as-needed ICS: 1.0 vs 1.1, P = .72). Compared with placebo, daily ICS in OW led to fewer annualized asthma symptom days (90.7 vs 41.2, P = .004) and exacerbations (1.4 vs 0.6, P = .006), while similar protective ICS effects were less apparent among NW.

CONCLUSIONS

In preschool children off controller therapy, OW is associated with greater asthma impairment and exacerbations. However, unlike older asthmatic patients, OW preschool children do not demonstrate reduced responsiveness to ICS therapy.

A new approach to the classification and management of airways diseases: identification of treatable traits

This review outlines a new, personalized approach for the classification and management of airway diseases. The current approach to airways disease is, we believe, no longer fit for purpose. It is impractical, overgeneralizes complex and heterogeneous conditions and results in management that is imprecise and outcomes that are worse than they could be. Importantly, the assumptions we make when applying a diagnostic label have impeded new drug discovery and will continue to do so unless we change our approach. This review suggests a new mechanism-based approach where the emphasis is on identification of key causal mechanisms and targeted intervention with treatment based on possession of the relevant mechanism rather than an arbitrary label. We highlight several treatable traits and suggest how they can be identified and managed in different healthcare settings.

Physiological Mechanisms of Airway Hyperresponsiveness in Obese Asthma

Obesity affects the incidence and severity of asthma in at least two major phenotypes: an early-onset allergic (EOA) form that is complicated by obesity and a late-onset nonallergic (LONA) form that occurs only in the setting of obesity. Both groups exhibit airway hyperresponsiveness to methacholine challenge but exhibit differential effects of weight loss. Measurements of lung function in patients with LONA obese asthma suggest that this group of individuals may simply be those unlucky enough to have airways that are more compliant than average, and that this leads to airway hyperresponsiveness at the reduced lung volumes caused by excess adipose tissue around the chest wall. In contrast, the frequent exacerbations in those with EOA obese asthma can potentially be explained by episodic inflammatory thickening of the airway wall synergizing with obesity-induced reductions in lung volume. These testable hypotheses are based on the strong likelihood that LONA and EOA obese asthma are distinct diseases. Both, however, may benefit from targeted therapeutics that impose elevations in lung volume.

Treadmill walking exercise modulates bone mineral status and inflammatory cytokines in obese asthmatic patients with long term intake of corticosteroids

BACKGROUND

Obesity and asthma are an important public health problem in Saudi Arabia. An increasing body of data supports the hypothesis that obesity is a risk factor for asthma. Asthma appears to be associated with low bone mineral density (BMD) due to long-term use of corticosteroids. Studies recently showed that weight bearing exercise training can increase mineral bone density, reduce weight and improve metabolic control.

OBJECTIVE

The present study aimed to measure the effects of treadmill walking exercises on bone mineral status and inflammatory cytokines in obese asthmatic patients treated with long term intake of corticosteroids.

METHODS

Eighty obese asthmatic patients of both sexes, their age ranged from 41 to 53 years. Subjects were divided into two equal groups: training group (group A) received aerobic exercise training on treadmill for six months in addition to the medical treatment where, the control group (group B) received only the medical treatment.

RESULTS

The results of this study indicated a significant increase in BMD of the lumbar spine & the radius, serum calcium and high density lipoprotein cholesterol (HDL-c) & significant reduction in parathyroid hormone, leptin, tumor necrosis factor- alpha(TNF-α), interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-6 (IL-6), low density lipoprotein cholesterol (LDL-c), triglycerides (TG) and body mass index (BMI) in group (A), while these changes were not significant in group (B).Also; there was a significant difference between both groups at the end of the study.

CONCLUSION

Treadmill walking exercise training is an effective treatment policy to improve bone mineral status and modulates inflammatory cytokines and blood lipids profile in obese asthmatic patients with long term intake of corticosteroids.

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.

Obesity and bronchodilator response in black and Hispanic children and adolescents with asthma

BACKGROUND

Obesity is associated with poor asthma control, increased asthma morbidity, and decreased response to inhaled corticosteroids. We hypothesized that obesity would be associated with decreased bronchodilator responsiveness in children and adolescents with asthma. In addition, we hypothesized that subjects who were obese and unresponsive to bronchodilator would have worse asthma control and would require more asthma controller medications.

METHODS

In the Study of African Americans, Asthma, Genes, and Environments (SAGE II) and the Genes-environments and Admixture in Latino Americans (GALA II) study, two identical, parallel, case-control studies of asthma, we examined the association between obesity and bronchodilator response in 2,963 black and Latino subjects enrolled from 2008 to 2013 using multivariable logistic regression. Using bronchodilator responsiveness, we compared asthma symptoms, controller medication usage, and asthma exacerbations between nonobese (< 95th% BMI) and obese (≥ 95th% BMI) subjects.

RESULTS

The odds of being bronchodilator unresponsive were 24% (OR, 1.24; 95% CI, 1.03-1.49) higher among obese children and adolescents compared with their not obese counterparts after adjustment for age, race/ethnicity, sex, recruitment site, baseline lung function (FEV1/FVC), and controller medication. Bronchodilator-unresponsive obese subjects were more likely to report wheezing (OR, 1.38; 95% CI, 1.13-1.70), being awakened at night (OR, 1.34; 95% CI, 1.09-1.65), using leukotriene receptor inhibitors (OR, 1.33; 95% CI, 1.05-1.70), and using inhaled corticosteroid with long-acting β2-agonist (OR, 1.37; 95% CI, 1.05-1.78) than were their nonobese counterpart. These associations were not seen in the bronchodilator-responsive group.

CONCLUSIONS

Obesity is associated with bronchodilator unresponsiveness among black and Latino children and adolescents with asthma. The findings on obesity and bronchodilator unresponsiveness represent a unique opportunity to identify factors affecting asthma control in blacks and Latinos.

Prospective Study on the Relationship of Obesity to Asthma Impairment and Risk

BACKGROUND

Although studies consistently show an association between obesity and increased asthma incidence, the role of obesity in asthma control is less clear.

OBJECTIVE

The objective of this study was to evaluate the association between baseline body mass index (BMI) and measures of subsequent asthma control in a large real-world cohort of adults with persistent asthma.

METHODS

In Kaiser Permanente Southern California (KPSC), a large managed care organization, we identified adults with persistent asthma in 2006, continuous health plan enrollment in 2007 and 2008, and a BMI measurement in 2006 or 2007. Each patient's last BMI measure in 2006 or 2007 was categorized into a BMI group: normal (<25 kg/m(2)), overweight (25-29.9 kg/m(2)), or obese (≥30 kg/m(2)). Asthma control outcomes in 2008 included asthma hospitalizations or emergency department visits (EDHO), oral corticosteroid dispensings linked to an asthma encounter (OCS), and dispensing of ≥7 short-acting beta-agonist canisters (SABA7). Multivariable analyses were conducted to assess the relationships of BMI categories with the risk of the asthma control outcomes after controlling for potential confounders.

RESULTS

In the 10,233 eligible adults-after adjusting for potential demographic, comorbidity, and prior utilization confounders-we found an increased relative risk (RR) of EDHO in overweight and obese (RR 1.40, 95% CI 1.10-1.78) individuals. Only obesity was associated in adjusted analyses with a significant increased relative risk of SABA7 (RR 1.27, 95% CI 1.15-1.40).

CONCLUSIONS

Elevated BMI, particularly obesity, is associated with subsequent poor asthma control, especially in the risk domain (exacerbations). These findings further support the importance of facilitating weight loss in overweight and obese adults with asthma.

Obesity and asthma: beyond T(H)2 inflammation

Obesity is a major risk factor for asthma. Likewise, obesity is known to increase disease severity in asthmatic subjects and also to impair the efficacy of first-line treatment medications for asthma, worsening asthma control in obese patients. This concept is in agreement with the current understanding that some asthma phenotypes are not accompanied by detectable inflammation, and may not be ameliorated by classical anti-inflammatory therapy. There are growing evidences suggesting that the obesity-related asthma phenotype does not necessarily involve the classical T(H)2-dependent inflammatory process. Hormones involved in glucose homeostasis and in the pathogeneses of obesity likely directly or indirectly link obesity and asthma through inflammatory and non-inflammatory pathways. Furthermore, the endocrine regulation of the airway-related pre-ganglionic nerves likely contributes to airway hyperreactivity (AHR) in obese states. In this review, we focused our efforts on understanding the mechanism underlying obesity-related asthma by exploring the T(H)2-independent mechanisms leading to this disease.

Mediator effect of depressive symptoms on the association between BMI and asthma control in adults

BACKGROUND

Obesity has been associated with worse asthma control. Depression has also been shown to be disproportionally prevalent among patients with asthma and among patients with obesity. However, no studies have examined the mediating effect of depression on the obesity-asthma relationship. This study examined the extent to which depressive symptoms may mediate the obesity-asthma relationship in an adult sample.

METHODS

A total of 798 patients with physician-diagnosed asthma were recruited from the outpatient asthma clinic at Hôpital du Sacré-Cœur de Montréal. Patients provided demographic and medical history information and completed a battery of questionnaires, including the Beck Depression Inventory (BDI)-II and the Asthma Control Questionnaire (ACQ). BMI was calculated from self-reported height and weight.

RESULTS

Analyses adjusted for age, sex, years of education, cohabitation, and inhaled corticosteroid dose revealed an association between BMI and ACQ (β = 0.017, P = .026), between BMI and BDI-II (β = 0.189, P = .002), and between BDI-II and ACQ (β = 0.044, P < .001). However, when both BDI-II and BMI were entered into the same model, BDI-II (β = 0.044, P < .001) but not BMI (β = 0.009, P = .226) remained significantly associated with ACQ.

CONCLUSIONS

The results indicate that depression and a high BMI are both associated with worse asthma control. However, consistent with our hypotheses, the relationship between BMI and worse asthma control was mediated by depressive symptoms. Future studies should examine the precise role of depressive symptoms in both weight and asthma control.

Developing and emerging clinical asthma phenotypes

For more than a century, clinicians have attempted to subdivide asthma into different phenotypes based on triggers that cause asthma attacks, the course of the disease, or the prognosis. The first phenotypes that were described included allergic asthma, intrinsic or nonallergic asthma, infectious asthma, and aspirin-exacerbated asthma. These phenotypes are being reviewed elsewhere in this issue of the journal. The present article focuses on developing and emerging clinical asthma phenotypes. First, asthma phenotypes that are associated with environmental exposures (occupational agents, cigarette smoke, air pollution, cold dry air); second, asthma phenotypes that are associated with specific symptoms or clinical characteristics (cough, obesity, adult onset of disease); and third, asthma phenotypes that are based on biomarkers. This latter approach is the most promising because it attempts to identify asthma phenotypes with different underlying mechanisms so that therapies can be better targeted toward disease-specific features and disease outcomes can be improved.

Is there a link between obesity and asthma?

Increasing epidemiological data identify a link between obesity and asthma incidence and severity. Based on experimental data, it is possible that shared inflammatory mechanisms play a role in determining this linkage. Although controversial, the role of adipokines may be central to this association and the maintenance of the asthma phenotype. While leptin and adiponectin have a causal link to experimental asthma in mice, data in humans are less conclusive. Recent studies demonstrate that adipokines can regulate the survival and function of eosinophils and that these factors can affect eosinophil trafficking from the bone marrow to the airways. In addition, efferocytosis, the clearance of dead cells, by airway macrophages or blood monocytes appears impaired in obese asthmatics and is inversely correlated with glucocorticoid responsiveness. This review examines the potential mechanisms linking obesity to asthma.

Linking obesity and asthma

A growing body of literature suggests that obesity has a significant impact on asthma risk, phenotype, and prognosis. Epidemiological studies have clearly demonstrated that asthma is more likely to occur in obese patients, and health status is impaired in obese individuals with asthma, with obese asthmatics experiencing more symptoms, worse quality of life, increased healthcare use, and increased asthma severity. However, obesity has well-described effects on lung function and mechanics that can lead to symptoms of dyspnea without causing the pathophysiologic changes of asthma. Adding to the challenges of evaluating this association, some studies have failed to demonstrate a robust relationship between obesity and traditional biomarkers of airway inflammation in adult asthmatics, leading to the conclusion that obesity does not necessarily worsen airway inflammation in asthma. In this regard, emerging data suggest that nonatopic mechanisms may be relevant in obese asthmatics, and that these mechanisms may have a direct impact on the response of obese asthmatics to asthma therapies, most notably inhaled glucocorticoids. This article will review selected aspects of the contributions of obesity-related airway and systemic inflammation to asthma, with a focus on the impact of obesity as a modifier of risk, prognosis, and therapeutic response in asthma.

Obesity in asthma: approaches to treatment

There is mounting evidence that obesity is associated with asthma, both of which are seeing a dramatic increase in prevalence. Not only is obesity a risk factor for the development of asthma but it is also associated with poor asthma control. Asthma phenotypes associated with obesity include early-onset allergic asthma and late-onset non-allergic asthma. The pathogenesis of the linkage is complex; obesity causes a variety of mechanical, metabolic, and immunological changes that can affect the airways. The treatment of asthma in obesity can be challenging, as obesity is associated with poor response to standard controller medications. A tailored approach that involves combining pharmacologic and non-pharmacologic therapies including weight loss, dietary interventions, and exercise, along with identification and treatment of obstructive sleep apnea, should therefore be considered in this population.

Reaching beyond disparity: safely improving asthma control in the at-risk African-American population

In the United States, substantial racial disparities exist in asthma prevalence, etiology, morbidity and mortality, particularly between African Americans and white Americans. African-American patients with asthma have inadequate access to appropriate healthcare, insufficient asthma management guidance from their physicians and poor adherence to asthma medications-all factors that may contribute to disproportionate morbidity. Historically, African Americans have been under-represented in clinical asthma studies, and a paucity of data exists surrounding asthma treatment response. One controversial study from 2006 suggests an increased safety risk with the use of long-acting beta2-adrenergic agonists (LABAs) in African Americans. More recently, several studies have evaluated the use of LABAs in combination with an ICS in African-American populations. This article reviews the existing data on asthma treatment outcomes, with particular emphasis on the recently published short- and long-term studies of ICS/LABA products conducted in African-American populations with moderate-to-severe asthma. Overall, evidence suggests that if African-American patients with asthma are provided with access to well-trained physicians, appropriate asthma management and effective medications, existing disparities in asthma control between African-American and white populations may be overcome.

Obesity and asthma: a coincidence or a causal relationship? A systematic review

BACKGROUND AND AIM

Epidemiological data has established increasing adiposity as a risk factor for incident asthma. However, the mechanisms underlying the association between obesity and asthma are incompletely understood. In the present paper, we review current knowledge of possible mechanisms mediating the observed association between obesity and asthma.

METHODS

Systematic literature review.

RESULTS

Obesity and asthma share some etiological factors, such as a common genetic predisposition and effects of in utero conditions, and may also have common predisposing factors such as physical activity and diet. Obesity results in important changes in the mechanical properties of the respiratory system which could explain the occurrence of asthma. However, there are also plausible biological mechanisms whereby obesity could be expected to either cause or worsen asthma. These include co-morbidities such as gastro-oesophageal reflux, complications from sleep-disordered breathing, breathing at low lung volumes, chronic systemic inflammation, and endocrine factors, including adipokines and reproductive hormones. Obesity related asthma is in general not associated with eosinophilic airway inflammation, and adipokines are likely to play important roles in the inflammatory pathogenesis of asthma in obese individuals.

CONCLUSION

The association between obesity and asthma is not straightforward, and further knowledge is clearly needed, as understanding the underlying mechanisms may lead to new therapeutic options for this high-risk part of the asthma population.

The treatment of asthma in obesity

The world is facing an unprecedented epidemic of obesity. This epidemic has led to major changes in the epidemiology of common diseases such as asthma. Obesity is a major risk factor for new-onset asthma. This article will discuss the role of mechanical and metabolic factors, as well as obesity-related comorbidities, in both causing airway disease and also affecting response to therapy in obese asthmatics. Asthma in obese individuals probably includes a spectrum of disease with at least two distinct phenotypes: early-onset allergic disease complicated by obesity and late-onset disease developing in the setting of obesity. Both phenotypes are distinct from asthma in lean individuals. Treatment of asthma in obesity needs to consider altered response to controller therapy, and the fact that mechanical factors, metabolic inflammation and other comorbidities are probably contributing to airway disease. Future studies should focus on the development of therapies specifically tailored towards the treatment of asthma in obesity.

Obesity and pulmonary disease: unanswered questions

Obesity is associated with risk of pulmonary disease, and adversely affects lung function. The parallel increase in obesity and asthma suggests the two conditions are linked; indeed, they can worsen each other. Obesity and inadequate asthma control are associated with poor quality of life, and place a high economic burden on public health. Although the obesity-lung interaction is a major issue for basic research and clinical studies, various questions remain unanswered. Do intrauterine and early life factors impact on the development of obesity and lung disease? If so, can this be prevented? Asthma is generally more severe in obese subjects, but is adiposity a driver of a new asthma phenotype that features greater morbidity and mortality, worse control and decreased response to medications? Obese individuals have small lung volumes, hence their airway calibre is reduced and airway resistance is increased. What puzzles physicians is whether peripheral airways undergo remodelling, which would increase bronchoconstriction. Obese asthmatics respond suboptimally to anti-inflammatory treatment, which raises the question: 'what drug for what patient?' Life expectancy is decreased in obesity and in chronic pulmonary disorders, but does obesity protect against or trigger chronic obstructive pulmonary disease? The time has come to find answers to these questions.

Obesity in asthma: more neutrophilic inflammation as a possible explanation for a reduced treatment response

BACKGROUND

The incidence of asthma and obesity is increasing worldwide, and reports suggest that obese patients have more severe asthma. We investigated whether obese asthma patients have more severe airway obstruction and airway hyper-responsiveness and a different type of airway inflammation than lean asthmatics. Furthermore, we assessed the effect of obesity on corticosteroid treatment response.

METHODS

Patient data from four well-documented asthma cohorts were pooled (n = 423). We evaluated FEV(1) , bronchial hyper-responsiveness (PC(20) ) to either methacholine/histamine or adenosine 5'-monophosphate (AMP) (differential) cell counts in induced sputum and blood and corticosteroid treatment response in 118 patients.

RESULTS

At baseline, FEV(1) , PC(20) methacholine or histamine, and PC(20) AMP values were comparable in 63 obese (BMI ≥ 30 kg/m(2) ) and 213 lean patients (BMI <25 kg/m(2) ). Obese patients had significantly higher blood neutrophils. These higher blood neutrophils were only seen in obese women and not in obese men. After a two-week treatment with corticosteroids, we observed less corticosteroid-induced improvement in FEV(1) %predicted in obese patients than in lean patients (median 1.7% vs 6.3% respectively, P = 0.04). The percentage of sputum eosinophils improved significantly less with higher BMI (P = 0.03), and the number of blood neutrophils increased less in obese than in lean patients (0.32 x10(3) /μl vs 0.57 x10(3) /μl, P = 0.046).

CONCLUSIONS

We found no differences in asthma severity between obese and nonobese asthmatics. Interestingly, obese patients demonstrated more neutrophils in sputum and blood than nonobese patients. The smaller improvement in FEV(1) and sputum eosinophils suggests a worse corticosteroid treatment response in obese asthmatics.

Higher prevalence of obesity among children with asthma

The aim of this study is to investigate the association between childhood obesity and asthma, and whether this relationship varies by race/ethnicity. For this population-based, cross-sectional study, measured weight and height, and asthma diagnoses were extracted from electronic medical records of 681,122 patients aged 6-19 years who were enrolled in an integrated health plan 2007-2009. Weight class was assigned based on BMI-for-age. Overall, 18.4% of youth had a history of asthma and 10.9% had current asthma. Adjusted odds of current asthma for overweight, moderately obese, and extremely obese youth relative to those of normal weight were 1.22 (95% confidence interval (CI): 1.20, 1.24), 1.37 (95% CI: 1.34, 1.40), and 1.68 (95% CI: 1.64, 1.73), respectively (P trend < 0.001). Black youth are nearly twice as likely (adjusted odds ratio (OR) = 1.93, 95% CI: 1.89, 1.99), and Hispanic youth are 25% less likely (adjusted OR = 0.75, 95% CI: 0.74, 0.77), to have current asthma than to non-Hispanic white youth. However, the relationship between BMI and asthma was strongest in Hispanic and weakest in black youth. Among youth with asthma, increasing body mass was associated with more frequent ambulatory and emergency department visits, as well as increased inhaled and oral corticosteroid use. In conclusion, overweight, moderate, and extreme obesity are associated with higher odds of asthma in children and adolescents, although the association varies widely with race/ethnicity. Increasing BMI among youth with asthma is associated with higher consumption of corticosteroids and emergency department visits.

Obesity, metabolic dysregulation and oxidative stress in asthma

BACKGROUND

Epidemiological data demonstrate an increased risk of developing incident asthma with increasing adiposity. While the vast majority of studies support the interaction between obesity and asthma, the causality is unclear.

SCOPE OF REVIEW

This article will review the current literature supporting the presence of an obese asthma phenotype and the possible mechanisms mediating the effects of obesity on asthma.

MAJOR CONCLUSIONS

Obesity is associated with poor asthma control, altered responsiveness to medications and increased morbidity. Obesity is characterized by systemic inflammation that may result in increased airway inflammation. However, this assertion is not supported by current studies that demonstrate a lack of significant airway inflammation in obese asthmatics. In spite this observation one must consider limitations of these studies including the fact that most subjects were treated with inhaled corticosteroids that would likely alter inflammation in the lung. Thus, it remains unclear if obesity is associated with alterations in inflammation in the airways of subjects with asthma. Hormones such as leptin and adiponectin are affected by obesity and may play a role in mediating innate immune responses and allergic responses, respectively. The role of oxidative stress remains controversial and the current evidence suggests that while oxidative stress is important in asthma, it does not fully explain the characteristics associated with this unique phenotype.

GENERAL SIGNIFICANCE

Obesity related asthma is associated with increased morbidity and differential response to asthma therapies. Understanding the mechanisms mediating this phenotype would have significant implications for millions of people suffering with asthma. This article is part of a Special Issue entitled Biochemistry of Asthma.