Effect of Obesity on Asthma Phenotype is Dependent upon Asthma Severity

Background. We recently reported that obese and non-obese patients with asthma have similar airflow limitation and bronchodilator responsiveness, but obese patients have more symptoms overall. There is limited information on the effect of obesity on asthmatics of varying severity measured by objective physiological parameters. Understanding how obesity affects asthmatics of differing severity can provide insights into the pathogenesis of asthma in the obese and a rationale for the therapeutic approach to such patients. Methods. Participants with asthma from two American Lung Association—Asthma Clinical Research Center (ALA-ACRC) studies were grouped by tertiles of airflow obstruction (forced expiratory volume in one second (FEV₁%) predicted, FEV₁/forced vital capacity (FVC)) and methacholine reactivity (PC₂₀FEV₁). Within each tertile, we examined the independent effect of body mass index (BMI), divided into normal weight, overweight, and obese categories, on lung function, airway reactivity, and symptoms. Results. Overall, both FEV₁ and FVC decreased and symptoms worsened with increasing BMI; airway reactivity was unchanged. When stratified by the degree of airflow obstruction, higher BMI was not associated with greater airway reactivity to methacholine. Higher BMI was associated with more asthma symptoms only in the least obstructed FEV₁/FVC tertile. When stratified by degree of airway reactivity, BMI was inversely associated with FVC in all PC₂₀FEV₁ tertiles. BMI was directly associated with asthma symptoms only in those with the least airway reactivity. Conclusions. Obesity does not influence airway reactivity in patients with asthma and it is associated with more symptoms only in those with less severe disease.     

The effect of obesity on pulmonary lung function of school aged children in Greece

Obesity impacts on many issues of pulmonary medicine, where it is debated if obesity is linked to asthma, atopy or altered lung function tests. Our study aimed to investigate primarily the effect of obesity on the lung function tests and secondary the possible link of obesity with atopy and asthma in a large cohort of children in Greece. Body mass index (BMI) and data from a questionnaire for lung health, atopy, nutritional habits and family history were obtained from 2,715 children aged 6–11 years. Six hundred fifty‐seven children with BMI>85th percentile (357 overweight, 300 obese) and a group of 196 normal weight children underwent spirometry. The % expected FVC, FEV₁, FEF_25–75, and FEV1/FVC were significantly reduced in overweight or obese children compared to children with normal weight (P = 0.007, P < 0.001, P < 0.001, and P < 0.001, respectively). Reported atopy was significantly higher in overweight or obese children compared to normal weight children (P = 0.008). High BMI remained a strong independent risk factor for asthma (OR = 2.17, 95% CI = 1.22–3.87, P = 0.009) and for atopy (OR = 2.06, 95% CI = 1.32–3.22, P = 0.002). The effect of increased BMI on asthma was significant in girls, but not in boys (OR = 2.73, 95% CI = 1.09–6.85, P = 0.032; OR = 1.74, 95% CI = 0.83–3.73, P = 0.137, respectively). In conclusion we have shown that high BMI remains an important determinant of reduced spirometric parameters, a risk factor for atopy in both genders and for asthma in girls. Pediatr Pulmonol. 2009; 44:273–280. © 2009 Wiley‐Liss, Inc.     

Pulmonary dysanapsis, methacholine airway responsiveness and sensitization to airborne antigen

Abstract Whether the disproportional growth of airways relative to lung parenchyma (dysanapsis) has any relationship to the development of non-specific bronchial hyperresponsiveness and atopy was investigated in 45 family members of the patients with atopic asthma. As indices of pulmonary dysanapsis, forced expiratory flow_25-75/forced vital capacity (FEF_25-75/FVC) and the tracheal cross sectional area divided by the forced expiratory volume (X-SA/FVC) were examined. As an index of non-specific airway responsiveness, the cumulative dose of inhaled methacholine needed to induce 35% reduction of respiratory conductance (PD₃₅) was determined by continuous respiratory resistance measurement. For examination of atopy, skin prick tests were conducted, and total serum IgE and IgE specific to common inhaled antigens were measured. FEF_25-75/FVC showed no significant correlation to FVC but showed a significant correlation to log (PD₃₅). When the analysis was done in the subjects whose FEVI/FVC was more than 0.8, FEF_25-75/FVC showed a significant negative correlation to FVC but lost its correlation to log(PD35). X-SA/FVC showed a significant negative correlation to FVC but had no significant correlation to log(PD₃₅). These relations were conserved when the analysis was done in subjects without airway obstruction. In addition, FEV₁/FVC had a significant correlation to log(PD₃₅) and FEF_25-75/FVC. However, subjects who had a positive IgE(MAST) had a significantly smaller X-SA/FVC than those with a negative IgE(MAST) (0.60 ± 0.14[SD] and 0.72 ± 0.18, respectively, P<0.02). These results suggest that although pulmonary dysanapsis does not have a significant relation to airway responsiveness to inhaled methacholine, it may be associated with sensitization to airborne antigens.     

Adipokines,asymmetrical dimethylarginine,and pulmonary function in adolescents with asthma and obesity

Objective: This study was to investigate whether the metabolic abnormalities of adipokines and asymmetrical dimethylarginine (ADMA) associate with pulmonary function deficits in adolescents with obesity and asthma. Methods: This study enrolled 28 obese adolescents with asthma, 46 obese adolescents without asthma, 58 normal-weight adolescents with asthma, and 63 healthy control subjects. Serum levels of leptin, high-molecule-weight (HMW) adiponectin, retinol binding protein 4 (RBP4), asymmetrical dimethylarginine (ADMA), and pulmonary function were qualified. Results: The obese subjects had higher levels of leptin and ADMA but lower levels of HMW adiponectin than the normal-weight subjects with or without asthma. The subjects with asthma had higher levels of RBP4 than those without asthma. The obese adolescents with asthma had lowest forced expiratory lung volume in the first second (FEV₁)/forced vital capacity (FVC) ratio among the four study groups. In all the study subjects and in the subjects with asthma alone, the FEV₁/FVC ratio associated negatively with leptin, however, such association was rendered non-significant when adjusted for BMI. The pulmonary function deficits associated inversely with BMI percentile in the subjects with asthma. However, the decreased FEV₁/FVC ratio was not correlated with HMW adiponectin, RBP4 or ADMA. Conclusions: Our present study confirmed obstructive pattern of pulmonary function characterized by the reduced FEV₁/FVC ratio in the obese adolescents with asthma. These pulmonary deficits were associated inversely with the increased BMI percentile.     

Body Mass Index-Percentile and Diagnostic Accuracy of Childhood Asthma

Objective. To determine whether high BMI-percentile is associated with misdiagnosis of asthma among children referred to an asthma specialist. Methods. We queried the electronic records of children 8 to 18 years of age seen by a Nemours pediatric pulmonologist. All visits during a 6-year period with the chief complaint of asthma, or an asthma-like symptom such as wheeze, cough, or dyspnea, were included. We collected spirometry, blood counts, and immunoglobulin E (IgE) if available. We determined whether the child had referring physician-diagnosed asthma, specialist-diagnosed asthma, or both. Specialist-diagnosed asthmatics who met additional objective “gold-standard” criterion were labeled strict-criterion asthma. Results. Prevalence of high BMI-percentile was extremely common in all defined asthma groups, even those meeting strict criteria for diagnosis. Referring physician-diagnosed asthmatics did not have higher rates of obesity, and referring physician-diagnosed asthmatics had objective indicators of asthma that were the same as asthmatics diagnosed by a specialist. There was good diagnostic correlation between referring physicians and asthma specialists that was not affected by BMI. Among specialist-diagnosed asthmatics, increased BMI-percentile associated with significantly reduced forced expiratory volume in 1 second (FEV₁), forced expiratory flow during the middle half of the forced vital capacity (FEF_{25 ? 75}), and FEV₁/forced vital capacity (FVC); and significantly increased total blood leukocytes, neutrophils, and platelets compared to leans. For all 2,258 referrals, the estimated odds ratio of receiving a specialist-diagnosis of asthma increased by 0.4% with each increasing BMI percentile. Conclusions. Referring physicians do not appear to erroneously diagnose children with asthma due to overweight status. Our data confirm that overweight status is extremely high in children with true asthma and likely increases the risk for true asthma. Although these data cannot discern causality, high BMI-percentile is associated with greater airflow obstruction and elevated markers of systemic inflammation that could contribute to underlying mechanisms of asthma.     

The Association of Overweight and Obesity with Spirometric Values in Minority Children Referred for Asthma Evaluation

Background. Overweight, obesity, and asthma are more prevalent in minority children; yet, the association of overweight and obesity with spirometric values in asthmatic minorities is not well characterized. Objective. To study the relationship between weight, ethnicity, and spirometric values in children referred for asthma evaluation to a large inner-city hospital in Bronx, NY. Methods. Retrospective review of spirometry done at the first pulmonary clinic visit of 980 asthmatic children, aged 7–20 years, was conducted. Linear regression analysis was performed to elucidate the association of overweight and obesity with pulmonary function among Whites, African Americans, and Hispanics compared with their normal weight counterparts. Results. More African Americans (58%) and Hispanics (65.4%) were overweight and obese than Whites (51.2%) (p < .05). Compared with their normal weight counterparts, percent forced expiratory volume in the 1st second (FEV₁)/forced vital capacity (FVC) ratio was lower in both overweight and obese African Americans (2.99%, p < .05 and 3.56%, p < .01, respectively) and Hispanics (2.64%, p < .05 and 2.36%, p < .05, respectively); these differences were found in obese (3.73%, p < .05) but not in overweight (0.68%, p = .7) Whites. Conclusions. FEV₁/FVC ratio was lower in both overweight and obese African American and Hispanic children, while this association was present only among obese Whites compared with their normal weight counterparts. These results suggest that spirometric measures of lower airway obstruction decrease with smaller weight increments in minority children when compared with White children. In the context of the higher prevalence of overweight and obesity among African Americans and Hispanics, our findings offer one potential explanation for increased asthma among minority children.     

Analysis of factors associated with bronchial hyperreactivity to methacholine in bronchiectasis

Nonspecific bronchial hyperreactivity (BHR) has been reported to occur in patients with bronchiectasis. To evaluate this further, we studied 77 patients with stable bronchiectasis (noncystic fibrosis) with special reference to the prevalence of BHR to methacholine (MCh), and its relation to lung function, sputum characteristics, concommitant asthma, and atopy. The concentration of MCh required to produce a fall of 20% in forced expiratory volume in 1 s (FEV₁), PC₂₀, was determined by Wright’s nebulization tidal breathing method. BHR defined by a PC₂₀ ≤ 8 mg/ml was found in 21 of 47 (45%) subjects who underwent bronchial challenge. Presence of BHR was positively associated with low baseline spirometric values, diagnosis of asthma, long duration of disease, and elevated total IgE on univariant analysis, and was significantly related to FEV₁/forced vital capacity (FVC) ratio and asthma on multiple regression analysis. Ten of the 21 hyperreactive subjects did not have clinical asthma, whereas all 11 of 22 subjects with clinical asthma who underwent bronchial challenge were hyperreactive. Among those with BHR, there was a positive correlation between PC₂₀ and baseline FEV₁. When patients were further classified into asthmatic and nonasthmatic subjects, a positive correlation between PC₂₀ and FEV₁ was seen only in those without asthma. Frequency of infective episodes and inflammatory score of sputum assessed by average daily volume, purulence, and leukocyte count did not differ significantly in the groups with and without BHR. These results suggest that BHR in patients with bronchiectasis is associated with coexistent asthma and worse spriometric values, and not with the severity of bronchial sepsis. An erratum to this article is available at .     

Bronchial Responsiveness,Spirometry and Mortality in a Cohort of Adults

Objective. Prospective population studies have reported that pulmonary function, measured by forced expiratory volume in one second (FEV₁), is an independent predictor for mortality. Besides, several studies found that death from all causes is higher in asthmatics than in non-asthmatics. However, none of these studies examined whether bronchial hyperresponsiveness (BHR), one of the key features in asthma, can be used as a predictor for mortality. Thus, the aim of this study was to analyze the association between BHR, FEV_1, and all-cause mortality in a population-based cohort of adults. Methods. Within the cross-sectional survey ECRHS-I Erfurt (1990–1992), 1162 adults aged 20–65 years performed lung function tests, including spirometry and BHR testing by methacholine inhalation up to a cumulative dose of 2 mg. BHR was assessed from the methacholine dose nebulized at ≥ 20% fall of FEV₁. After circa 20 years of follow-up, the association between baseline lung function, BHR, and mortality was investigated. Results. A total of 85 individuals (7.3%) died during a mean follow-up period of 17.4 years (SD = 2.4). FEV₁, but not forced vital capacity (FVC), was a predictor for mortality. In men, BHR increased the mortality risk (OR = 2.6, 95% CI: 1.3–5.3; adjusted for age and BMI). Additional adjustment for asthma did not change the results (OR = 2.4, 95% CI: 1.2–5.0). However, after an additional adjustment for pack years of cigarette smoking or airway obstruction, the association was not statistically significant anymore (OR = 1.8, 95% CI: 0.8–4.0, OR = 1.9, 95% CI: 0.9–4.3, respectively). Conclusions. BHR was associated with an increased mortality risk in men. Potential explanatory factors for this association are cigarette smoking, chronic obstructive pulmonary disease (COPD), or asthma. Thus, BHR might be an indirect predictor for all-cause mortality. FEV₁ was an independent predictor for all-cause mortality.     

Gender differences in effects of obesity and asthma on adolescent lung function: Results from a population-based study

Objective: To investigate lung function associated with asthma and body mass index (BMI) among adolescents at 96 northern Taiwan junior high schools participating in an asthma screening program. Methods: The questionnaires and lung function test results measured for 3669 boys and 3523 girls were included in this study for data analysis. Measures of forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁) and FEV₁/FVC ratio were compared by sex, asthma status and BMI. Results: Overall mean FVC levels were similar between students with and without asthma, 3.71 L vs. 3.71 L for boys (p = 0.991) and 2.79 vs. 2.78 for girls (p = 0.517). The overall mean FEV₁ levels were also similar between girls with and without asthma. Asthmatic boys had lower FEV₁ than non-asthmatic boys. Mean FEV₁/FVC was significantly lower in students with asthma than those without asthma. Mean FVC and FEV₁ increased with BMI in both sexes. A lower mean FEV₁/FVC was observed among students with asthma and high BMI, and was more pronounced in boys than in girls. Multivariable regression analysis also showed that FEV₁/FVC ratios were negatively associated with asthma and high BMI, stronger in boys than in girls for asthma (β = ?2.176 (standard errors (SE) = 0.268) vs. ?1.085 (SE = 0.258) and for BMI (β = ?0.309 (SE = 0.025) vs. ?0.218 (SE = 0.029)). Conclusion: This northern Taiwan study suggests that FEV₁/FVC is negatively associated with asthma and high BMI in adolescents, stronger for boys than for girls.     

Relationship Among Pulmonary Function, Bronchial Hyperresponsiveness, and Atopy in Children with Clinically Stable Asthma

Pulmonary function testing plays a key role in the diagnosis and management of asthma in children. However, the literature does not clearly show whether children with clinically stable asthma have significantly reduced lung function when compared with normal children. We compared the lung function of 242 clinically stable asthmatic children who were initially diagnosed with mild intermittent or mild persistent asthma with the lung function of 100 nonasthmatic controls. The lung function was assessed using FEV₁, FEV₁/FVC, FEF_25–75 and PEF. In addition, we measured bronchial hyperresponsiveness (BHR) using the provocation concentration of methacholine needed to produce a 20% fall in FEV₁. All measures of pulmonary function were significantly decreased in the children with asthma. Pulmonary function was not influenced by atopy, serum IgE, or total eosinophil count (TEC). However, the likelihood ratio for trends revealed a significant association between our pulmonary parameters and the degree of BHR. Children with mild-to-severe BHR had greatly decreased lung function compared with those with normal BHR, the control group. In addition, a direct correlation was found between PC₂₀ and our pulmonary parameters in asthmatic children. However, only atopic children with asthma had a significant correlation between PC₂₀ and TEC. We found children with clinically stable asthma to have pulmonary obstruction, which associated strongly with their degree of BHR.     

Effects of posture on lung function in obese children

Forced expiratory manoeuvres are recommended performed in sitting posture; however, standing posture has been reported to be usually more advantageous since any diaphragmatic restriction associated with obesity is reduced. Information on the effect of posture on forced expiratory manoeuvres in obese children is lacking. Aim: To determine whether lung function measured in standing compared with sitting posture is increased in overweight and obese children. Methods: One hundred fifteen overweight (n = 23) and obese (n = 92) children (7–17 years old) performed forced expiratory flow‐volume manoeuvres in sitting and standing posture in random order. Results: Forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and forced expiratory flow after 50% of FVC (FEF₅₀) was significantly higher in sitting compared with standing posture [0.8, 1.1 and 2.2 percentage change in absolute values (all with P < 0.05)]. FEV₁/FVC and peak expiratory flow were not significantly different measured in sitting and standing posture; 95%–99% of the variance were explained by differences among individuals (all with P < 0.0001). Conclusions: In conclusion, FEV₁, FVC and FEF₅₀ were all significantly higher when measured in sitting compared with standing posture; however, the improvements were of little clinical significance. These findings confirm that sitting posture is appropriate in obese children when performing forced expiratory flow‐volume manoeuvres. Please cite this paper as: Berntsen B, Edvardsen E, Carlsen K‐H, Kolsgaard MLP and Carlsen KCL. Effects of posture on lung function in obese children. Clin Respir J 2011; 5: 252–257.     

Childhood asthma and GOLD‐defined chronic obstructive pulmonary disease

Background: Current understanding of chronic obstructive pulmonary disease (COPD) is that it results from an interaction of genetic and environmental factors. This study aimed to investigate the strength of association of various known risk factors for COPD. Methods: Detailed written questionnaires, full pulmonary function tests and atopy testing were completed in 749 people, aged 25–75 years, recruited from a random population sample. COPD was defined, using Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, as a post‐bronchodilator forced expiratory volume in 1 s/forced vital capacity (FEV₁/FVC) ratio <0.7. Results: The prevalence of COPD was higher in men (OR 1.7 (95% CI 1.1–2.7)) and increased with increasing age (OR per decade older 2.1 (95% CI 1.7–2.7)). COPD was more frequent in current and ex‐smokers and increased with increasing pack years (OR per 10 pack years 1.3 (95% CI 1.1–1.5)). On a logit scale, a diagnosis of asthma as a child conferred a similar risk as an increase in age of 22 years or 62 pack years of cigarette smoking. Conclusion: Childhood asthma emerged with the strongest association for GOLD‐defined COPD. Possible explanations for this are suggested, including limitations of the current GOLD spirometric definition of COPD, a chance observation because of the high prevalence of both disorders in this population, or alternatively childhood asthma is a risk factor for COPD.     

Usefulness of Exhaled Nitric Oxide for Diagnosing Asthma

Rationale. A standard asthma diagnosis is made based on clinical history, reversibility of airway obstruction, and bronchial hyperresponsiveness. Fractional exhaled nitric oxide (FeNO) is a noninvasive airway inflammatory marker that has been suggested as a diagnostic tool for asthma. The aim of this study was to establish a FeNO cut-off value for asthma diagnosis. Methods. One hundred and fourteen consecutive adult patients (mean age 34 ± 13 years) reporting symptoms consistent with asthma, with normal spirometric parameters and a negative bronchodilator test, were included in the study. All underwent a methacholine challenge test following the five-breath dosimeter protocol. FeNO was measured with a portable device (NioxMino, Aerocrine AB, Sweden) just before the methacholine challenge. The sensitivity, specificity, and diagnostic performance of FeNO measurement were calculated. Results. Thirty-five out of the 114 patients (30.7%) were diagnosed with asthma. A positive methacholine challenge was associated with higher FeNO levels and with lower forced expiratory volume in one second (FEV₁) at baseline. No correlation was found between methacholine provocative concentration causing a decrease of 20% in FEV₁ (PC₂₀) and FeNO levels. A receiver-operating characteristic curve was constructed for FeNO levels (area under the curve [AUC]: 0.762; 95% confidence interval [CI]: 0.667-0.857; p < .001). The FeNO cut-off point with maximal specificity and sensitivity for asthma diagnosis was 40 ppb. Conclusions. Patients with confirmed asthma showed higher FeNO levels. A cut-off value of 40 ppb was calculated as the most efficient for asthma diagnosis in our population. The use of FeNO measurement may be a helpful tool to rule out a diagnosis of asthma, especially in patients in whom a methacholine challenge is not feasible or available.     

Predictive Value of sGaw,FEF25 − 75, and FEV1 for Development of Asthma after a Negative Methacholine Challenge Test

Background. A 20% change in forced expiratory volume in 1 second (FEV₁) during methacholine challenge testing (MCT) is a reliable marker of asthma. When the FEV₁ decrease is < 20%, there is controversy whether other changes in flows and conductance may be useful. We conducted this study to determine whether changes in sGaw, FEF_{25 ? 75}, and FEV₁ in a negative MCT could predict future occurrence of asthma over a 3-year period. Methods. A total of 100 consecutive patients with clinical suspicion of asthma but who had a negative MCT per ATS FEV₁ criteria (< 20% FEV₁ decline at 16 mg/mL of methacholine) performed by the 5-breath dosimeter method were analyzed. Two pulmonary fellows, blinded to MCT results, reviewed the patients' medical records. Patients were classified into one of three categories: asthmatic, unclear, and not asthmatic. Decreases in sGaw, FEF_{25 ? 75}, and FEV₁ in the five groups were then retrieved. Analysis of variance (ANOVA) was used for data analysis. Results. Of 100 patients, 23 were excluded owing to lack of a 3-year follow-up. After complete data review, the number of patients (n) in each group was as follows: asthmatic (n = 15), unclear (n = 7), and not asthmatic (n = 55). sGaw and FEF_{25 ? 75} decreases from the negative MCT could not predict asthma; however, decreases in FEV₁ were associated with future asthma occurrence (sGaw p = 0.21, FEF25-75 p = 0.07, FEV₁ p = 0.0009). Forty-three percent of the patients who had a 10% to 20% decline in FEV₁ eventually developed asthma. Conclusion. Up to 20% of patients who have symptoms suggestive of asthma but a negative MCT can still develop asthma. Declines in sGaw and FEF_{25 ? 75} in a negative MCT appear to have no clinical significance. A decrease in FEV₁, especially 10% to 20%, is associated with the diagnosis of future asthma.     

The influence of gender and atopy in the relationship between obesity and asthma in childhood

BackgroundThe objective of the study was to examine the relationship between asthma and overweight–obesity in Spanish children and adolescents and to determine whether this relationship was affected by gender and atopy.MethodsThe study involves 8607 Spanish children and adolescents from the International Study of Asthma and Allergies in Childhood phase III. Unconditional logistic regression was used to obtain adjusted odds ratios (OR) and 95% confidence intervals (95% CI) for the association between asthma symptoms and overweight–obesity in the two groups. Afterwards, it was stratified by sex and rhinoconjunctivitis.ResultsThe prevalence of overweight and obesity in 6–7-year-old children was 18.6% and 5.2% respectively and in 13–14 year-old teenagers was 11.4% and 1.1% respectively. Only the obese children, not the overweight children, of the 6–7 year old group had a higher risk of any asthma symptoms (wheezing ever: OR 1.68 [1.15–2.47], asthma ever: OR 2.29 [1.43–3.68], current asthma 2.56 [1.54–4.28], severe asthma 3.18 [1.50–6.73], exercise-induced asthma 2.71 [1.45–5.05]). The obese girls had an increased risk of suffering any asthma symptoms (wheezing ever: OR 1.73 [1.05–2.91], asthma ever: OR 3.12 [1.67–5.82], current asthma 3.20 [1.65–6.19], severe asthma 4.83[1.94–12.04], exercise-induced asthma 3.68 [1.67–8.08]). The obese children without rhinoconjunctivitis had a higher risk of asthma symptoms.ConclusionsObesity and asthma symptoms were associated in 6–7 year-old children but not in 13–14 year-old teenagers. The association was stronger in non-atopic children and obese girls.     

Exhaled Carbon Monoxide in Asthmatic Adults with Bronchial Reactivity: A Prospective Study

Hypothesis. We hypothesized that eCO may permit non-invasive assessment of disease activity in adults with asthma and bronchial reactivity. Methods. A total of 209 participants 18 to 65 years of age with a diagnosis of asthma and bronchial reactivity provided data for analysis. The association between eCO and bronchial reactivity, forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), peak expiratory flow rate measurements (PEFR), asthma symptoms score, and bronchodilator use cross-sectionally and within-subject change in eCO were analyzed in relation to change in these variables over 6 weeks. Results. There was no difference in eCO in those who were taking inhaled corticosteroids and those who were not (p = 0.33). There was also no cross-sectional or within-in subject association between eCO and bronchial reactivity, FEV₁, FVC, PEFR, symptoms score, or bronchodilator use. Conclusions. In a population of adults with bronchial reactivity, eCO has no or very limited potential as a biomarker of asthma activity.     

Clinical characterization of children with resistant airflow obstruction,a multicenter study

Objective: To characterize a cohort of children with airflow limitation resistant to bronchodilator (BD) therapy. Methods: Pulmonary function tests performed in children 6–17 years of age at 15 centers in a clinical research consortium were screened for resistant airflow limitation, defined as a post-BD FEV₁ and/or an FEV₁/FVC less than the lower limits of normal. Demographic and clinical data were analyzed for associations with pulmonary function. Results: 582 children were identified. Median age was 13 years (IQR: 11, 16), 60% were males; 62% were Caucasian, 28% were African-American; 19% were obese; 32% were born prematurely and 21% exposed to second hand smoke. Pulmonary diagnoses included asthma (93%), prior significant pneumonia (28%), and bronchiectasis (5%). 65% reported allergic rhinitis, and 11% chronic sinusitis. Subjects without a history of asthma had significantly lower post-BD FEV₁% predicted (p = 0.008). Subjects without allergic rhinitis had lower post-BD FEV₁% predicted (p = 0.003). Children with allergic rhinitis, male sex, obesity and Black race had better pulmonary function post-BD. There was lower pulmonary function in children after age 11 years without a history of allergic rhinitis, as compared to those with a history of allergic rhinitis. Conclusions: The most prevalent diagnosis in children with BD-resistant airflow limitation is asthma. Allergic rhinitis and premature birth are common co-morbidities. Children without a history of asthma, as well as those with asthma but no allergic rhinitis, had lower pulmonary function. Children with BD-resistant airflow limitation may represent a sub-group of children with persistent obstruction and high risk for life-long airway disease.     

Is Exhaled Nitric Oxide a Useful Adjunctive Test for Assessing Asthma?

Rationale. To determine the general utility of clinical (Asthma Control Test) and physiologic (forced expiratory volume in the first second of exhalation [FEV₁] and fractionated exhaled nitric oxide level [FeNO]) parameters for characterizing asthma patients. Methods. Two cross-sectional independent studies simultaneously enrolled 100 patients in the US and 109 patients in Spain ≥ 18 years of age with a physician-diagnosis of asthma and confirmed by a ≥ 12% improvement in FEV₁ after bronchodilators or the presence of airway hyperresponsiveness, a central feature of asthma, as measured by methacholine challenge (PC₂₀ < 10 mg/mL). There was no restriction on asthma severity or treatment. Patients were excluded if they had a diagnosis of chronic obstructive pulmonary disease and/or were current cigarette smokers. Statistical analyses were performed to compare ACT, FeNO, and spirometry within and between sites. Results. Population characteristics revealed significant differences in distributions of age, percent-predicted FEV₁ (%FEV₁), FeNO, inhaled corticosteroid usage, and atopy between the two populations. The Spain site enrolled younger patients with milder asthma, based on higher %FEV₁ values and less frequent treatment with inhaled corticosteroids. At each site, mean FeNO levels decreased as asthma control categories increased, and means were lower in the US. There was a negative correlation between ACT and FeNO that was statistically significant for Spain patients not treated with inhaled corticosteroids. Conclusions. The results of this study support the use of FeNO as an adjunctive tool for assessing asthma primarily in mild inhaled corticosteroid (ICS)-naïve asthma patients. The lack of correlation of ACT with FeNO in this and other studies across the entire population appears to reflect the heterogeneity of asthma patients who have an admixture of asthma severity and treatment regimens making it very difficult to appreciate the nuances of sensitive tests like FeNO.     

Association between low pulmonary function and metabolic risk factors in Korean adults: the Korean National Health and Nutrition Survey

Impaired lung function is a risk factor for cardiovascular events and mortality. In addition, lung function impairment is also associated with insulin resistance and type 2 diabetes mellitus. It is well known that a common mechanism, such as insulin resistance and obesity, underlies metabolic syndrome. Our aim was to evaluate the association between impaired lung function and metabolic risk factors using data from a nationwide survey of chronic obstructive pulmonary disease prevalence in Korea and the Korean National Health and Nutrition Survey in 2001. The study population included 4001 subjects (aged ≥18 years) who underwent spirometry at least twice. We analyzed the association of low pulmonary function with metabolic syndrome components using multiple linear regression and also analyzed the association of metabolic syndrome with restrictive lung disease and obstructive lung disease using multiple logistic regression adjusted for waist to height ratio, sex, age, smoking, and the other covariates. Waist girth, systolic blood pressure, and triglyceride were associated with forced vital capacity (FVC); and only triglyceride was so with forced expiratory volume in 1 second (FEV₁), but not with FEV₁/FVC ratio. The odds ratio of metabolic syndrome for restrictive lung disease (FVC <80%, FEV₁/FVC >0.7) was 1.40 (95% confidence interval, 1.01-1.98), and that for obstructive lung disease (FEV₁/FVC <0.7) was 0.93 (95% confidence interval, 0.67-1.28) after adjustment for covariates. These results indicate that low pulmonary function in the general population is associated with clustering of metabolic syndrome risk factors and, furthermore, that restrictive lung disease is also related to metabolic syndrome.     

High Screen Time Is Associated with Asthma in Overweight Manitoba Youth

Objective. Low physical activity and high sedentary behavior are associated with adverse health outcomes, including asthma. The purposes were to (1) determine if low physical activity and/or high screen time increase the risk of asthma and airway hyperresponsiveness (AHR) in youth and (2) determine if weight status modifies these associations. Methods. This is a prospective cohort study of healthy weight and overweight Canadian youth. In 2003–2005, 723 youth (8.6 ± 0.5 years; 34.0% asthma, 55.9% boys) were recruited from the 1995 Manitoba Prospective Cohort Study. In 2008–2010, 489 returned for follow-up measures (30.9% asthma, 56.6% boys). The primary exposure variables were parent-reported physical activity and screen time at 8–10 years of age. The primary outcome measures were pediatric allergist-defined asthma and AHR defined as the provocative concentration of methacholine required to induce a 20% fall in forced expiratory volume in 1 second (FEV₁). Results. Low physical activity (≤2 times weekly) was not associated with asthma or AHR. However, high screen time (≥1 hour/day) was associated with a greater odds of asthma at baseline (odds ratio (OR) = 2.01, 95% confidence interval (CI) = 1.20–3.37, p < .01) and follow-up (OR = 2.11, 95% CI = 1.14–3.89, p < .02) versus low screen time. This association was more pronounced among overweight youth (baseline: OR = 3.95, 95% CI = 1.70–9.12, p < .0001; follow-up: OR = 3.22, 95% CI = 1.17–8.86, p < .02). Screen time was not associated with AHR at baseline or follow-up. Conclusions. High screen time increases the risk of asthma, particularly among overweight youth. Screen time, in addition to physical activity, should be included in clinical assessments of youth with asthma.