Sex specificity of asthma associated with objectively measured body mass index and waist circumference: the Humboldt study

Impact of sex on severe asthma: a cross-sectional retrospective analysis of UK primary and specialist care

INTRODUCTION

After puberty, females are more likely to develop asthma and in a more severe form than males. The associations between asthma and sex are complex with multiple intrinsic and external factors.

AIM

To evaluate the sex differences in the characteristics and treatment of patients with severe asthma (SA) in a real-world setting.

METHODS

Demographic, clinical and treatment characteristics for patients with SA in the UK Severe Asthma Registry (UKSAR) and Optimum Patient Care Research Database (OPCRD) were retrospectively analysed by sex using univariable and multivariable logistic regression analyses adjusted for year, age and hospital/practice.

RESULTS

3679 (60.9% female) patients from UKSAR and 18 369 patients (67.9% female) from OPCRD with SA were included. Females were more likely to be symptomatic with increased Asthma Control Questionnaire-6 (UKSAR adjusted OR (aOR) 1.14, 95% CI 1.09 to 1.18) and Royal College of Physicians-3 Question scores (OPCRD aOR 1.29, 95% CI 1.13 to 1.47). However, they had a higher forced expiratory volume in 1 second per cent (FEV1%) predicted (UKSAR 68.7% vs 64.8%, p<0.001) with no significant difference in peak expiratory flow. Type 2 biomarkers IgE (UKSAR 129 IU/mL vs 208 IU/mL, p<0.001) and FeNO (UKSAR 36ppb vs 46ppb, p<0.001) were lower in females with no significant difference in blood eosinophils or biological therapy. Females were less likely to be on maintenance oral corticosteroids (UKSAR aOR 0.86, 95% CI 0.75 to 0.99) but more likely to be obese (UKSAR aOR 1.67, 95% CI 145 to 1.93; OPCRD SA aOR 1.46, 95% CI 1.34 to 1.58).

CONCLUSIONS

Females had increased symptoms and were more likely to be obese despite higher FEV1% predicted and lower type 2 biomarkers with consistent and clinically important differences across both datasets.

Risk of asthma and/or wheezing in obese individuals with or without metabolic syndrome: From the Korea National Health and Nutrition Examination Survey data

Introduction: Obesity increases the risk of asthma; however, whether metabolic syndrome (MS), with obesity being one of its five components, is also associated with increased asthma risk remains unclear. Objective: To investigate the association between the risk of asthma and obesity, MS, and each component of MS. Methods: We performed a cross-sectional study of 41,480 Korean adults by using data from the 2007-2016 Korean National Health and Nutrition Examination Survey. Asthma was defined as a history of physician-diagnosed asthma or wheezing sound within the past 12 months. Results: The adjusted odds ratio (OR) for asthma was significantly increased in participants with obesity (OR 1.30 [95% confidence interval {CI}, 1.27-1.33]; p < 0.0001) and MS (OR 1.23 [95% CI, 1.20-1.25]; p < 0.0001). Obesity and MS showed an additive effect (OR 1.38 [95% CI, 1.34-1.41]; p < 0.001), followed by obesity(+)MS(-) (OR 1.28 [95% CI, 1.25-1.31]; p < 0.001) and obesity(-)MS(+) (OR 1.14 [95% CI, 1.10-1.18]; p < 0.001). Among each metabolic component, only abdominal obesity (OR 1.28 [95% CI, 1.24-1.32]; p < 0.001) and hypertension (OR 1.16 [95% CI, 1.12-1.20]; p < 0.001) significantly increased the risk of asthma. Unlike the female patients (OR 1.39 [95% CI, 1.35-1.43]; p < 0.001), having MS showed a lower risk of asthma in the male patients (OR 0.79 [95% CI, 0.75-0.82]; p < 0.001). Conclusion: The risk of asthma was highest when both obesity and MS were present, followed by obesity alone and MS alone. Abdominal obesity and hypertension were associated with an increased asthma risk, and there was a sex difference that MS lowered the risk of asthma in Korean male patients.

Metformin prevents airway hyperreactivity in rats with dietary obesity

Increased insulin is associated with obesity-related airway hyperreactivity and asthma. We tested whether the use of metformin, an antidiabetic drug used to reduce insulin resistance, can reduce circulating insulin, thereby preventing airway hyperreactivity in rats with dietary obesity. Male and female rats were fed a high- or low-fat diet for 5 wk. Some male rats were simultaneously treated with metformin (100 mg/kg orally). In separate experiments, after 5 wk of a high-fat diet, some rats were switched to a low-fat diet, whereas others continued a high-fat diet for an additional 5 wk. Bronchoconstriction and bradycardia in response to bilateral electrical vagus nerve stimulation or to inhaled methacholine were measured in anesthetized and vagotomized rats. Body weight, body fat, caloric intake, fasting glucose, and insulin were measured. Vagally induced bronchoconstriction was potentiated only in male rats on a high-fat diet. Males gained more body weight, body fat, and had increased levels of fasting insulin compared with females. Metformin prevented development of vagally induced airway hyperreactivity in male rats on high-fat diet, in addition to inhibiting weight gain, fat gain, and increased insulin. In contrast, switching rats to a low-fat diet for 5 wk reduced body weight and body fat, but it did not reverse fasting glucose, fasting insulin, or potentiation of vagally induced airway hyperreactivity. These data suggest that medications that target insulin may be effective treatment for obesity-related asthma.

Early-pregnancy transcriptome signatures of preeclampsia: from peripheral blood to placenta

Several studies have linked maternal asthma, excess BMI, and low vitamin D status with increased risk of Preeclampsia (PE) development. Given prior evidence in the literature and our observations from the subjects in the Vitamin D Antenatal Asthma Reduction Trial (VDAART), we hypothesized that PE, maternal asthma, vitamin D insufficiency, and excess body mass index (BMI) might share both peripheral blood and placental gene signatures that link these conditions together. We used samples collected in the VDAART to investigate relationships between these four conditions and gene expression patterns in peripheral blood obtained at early pregnancy. We identified a core set of differentially expressed genes in all comparisons between women with and without these four conditions and confirmed them in two separate sets of samples. We confirmed the differential expression of the shared gene signatures in the placenta from an independent study of preeclampsia cases and controls and constructed the preeclampsia module using protein-protein interaction networks. CXC chemokine genes showed the highest degrees of connectivity and betweenness centrality in the peripheral blood and placental modules. The shared gene signatures demonstrate the biological pathways involved in preeclampsia at the pre-clinical stage and may be used for the prediction of preeclampsia.

Evaluation of Interleukin-6, Leukotriene B-4, and Nitric Oxide Levels in Exhaled Breath Condensate of Asymptomatic Obese Individuals: Are Obese Patients Under Risk of Developing Asthma?

Objective

If systemic inflammation in relation with obesity causes asthma, the detection of increased airway inflammation among obese individuals who do not have any respiratory symptoms can be also beneficial in indentifying obese patients who are at risk of developing asthma. The aim of this study was to evaluate the systemic and airway inflammation of asymptomatic obese and non-obese individuals.

Materials and Methods

Obese and non-obese individuals with no respiratory symptoms were included. Inflammatory biomarkers such as C-reactive protein (CRP), exhaled breath condensate (EBC) interleukin-6 (IL-6), EBC leukotriene B-4 (LTB-4), and EBC nitric oxide (NO) levels of obese and non-obese individuals were determined.

Results

Forty-five obese individuals (body mass index [BMI]≥30) and 31 non-obese individuals (BMI≤25) as a control group were included in this study. The mean age of the obese group (38.7±11.4 years) was significantly higher than the one of the non-obese group (29.5±8.6 years; p<0.001). There was no significant relationship between gender and BMI (χ² =1.471, p=0.225). CRP levels were significantly higher in the obese group (6.94±8.28) than the non-obese group (3.29±0.39; p<0.001). The levels of EBC IL-6 in obese and non-obese group were found as 22.61±12.53 and 21.08±14.39, respectively (p=0.624). There was no significant difference between EBC NO levels of the obese group and non-obese group (24.35±10.9 vs. 21.56±7.83; p=0.226). No significant difference was found between the EBC LTB-4 level in the obese group and the non-obese group (36.39±89.82 vs. 16.64±17.45; p=0.231).

Conclusion

Increased systemic inflammation in obese individuals who had no respiratory symptoms might indicate the tendency of asthma. However, airway inflammation was not significantly different between groups. Therefore the relationship between obesity and asthma should be investigated in future large-scale studies determining the direct effects of adipokines on airways.

Association between abdominal obesity and asthma: a meta-analysis

Background

Studies evaluating the association between abdominal obesity and asthma yielded conflict results. Whether abdominal obesity is positively associated with asthma remains unclear.

Objective

To quantitatively determine the association between abdominal obesity and asthma.

Methods

Databases including PubMed, Web of Science, China National Knowledge Infrastructure, China Biology Medicine disc, Chinese Scientific and Technological Journal Database and Wanfang Data were searched up to February 2018 to collect all relevant studies. Reference lists of related articles were also checked. After study selection and data extraction, meta-analysis was conducted to calculate the pooled odds ratio (OR) and corresponding 95% confidence interval (CI). Subgroup analyses by study design and age groups of participants were further performed. Publication bias was assessed via Begg’s rank correlation and Egger’s linear regression methods.

Results

A total of 13 studies were included in the final meta-analysis, including 2 case–control studies, 6 cohort studies, and 5 cross-sectional studies. Our meta-analysis observed a positive association between abdominal obesity and asthma (OR = 1.47, 95% CI 1.35–1.59). No evidence of heterogeneity (I² = 10.7%) or publication bias (Begg’s test P = 0.200, Egger’s test P = 0.146) was found. Subgroup analyses by study design and age groups of participants obtained consistently positive results across subgroups. Moreover, our meta-analysis observed similar results when considering this association separately in males and females (Males: OR = 1.37, 95% CI 1.18–1.58; Females: OR = 1.39, 95% CI 1.22–1.58). In addition, the association between abdominal overweight and asthma was further explored in this meta-analysis and the pooled OR and 95% CI was 1.13 (1.03, 1.24), indicating that there is a dose–response relationship between abdominal weight status and asthma.

Conclusions

Our meta-analysis shows a positive association between abdominal obesity and asthma. Moreover, this association is similar in males and females. In addition, our meta-analysis indicates that there is a dose–response relationship between abdominal weight status and asthma. Therefore, addressing abdominal obesity issue is of great importance. More studies are needed in the future to clarify the association between abdominal obesity and asthma.

Asthma alleviates obesity in males through regulating metabolism and energy expenditure

Many epidemiological studies suggested a correlation between obesity and asthma. However, little is known about the molecular details explaining this correlation. Here, we show that asthma decreased body weight of asthmatic male mice fed with high fat diet via increasing energy expenditure and insulin sensitivity. The increase of energy expenditure was mainly due to upregulation of pAMPK and Sirt1. The activation of AMPK/Sirt1/PGC1α signaling promoted the expression of the thermogenic genes like ucp1, PRDM16, cidea, Elovl3, PPARα, which occurred in brown adipocyte tissue and subcutaneous white adipose tissue. Besides, by activating IL33/ILC2/AAMac pathway in subcutaneous white adipose tissue, asthma promoted subcutaneous white adipose tissue into beige fat. In addition, insulin sensitivity was improved in the asthmatic male mice by decreasing the expression of G6Pase in the liver, which was recapitulated in HepG2. In human, we found that Body Mass Index (BMI) and waist circumference were significantly lower in males suffering asthma compared with the control in the National Health and Nutrition Examination Survey (NHANES) cohort. These data together suggest asthma in males decreases obesity by improving the metabolism function of brown and subcutaneous adipose tissue, and decreasing insulin resistant in the liver.

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.

Association between anthropometric markers and asthma control, quality of life and pulmonary function in adults with asthma

BACKGROUND

The role of abdominal fat and body fat (BF) in the evaluation of nutritional status in asthma has been considered recently. The present study aimed to evaluate the association between different anthropometric markers and asthma control, pulmonary function and quality of life. A secondary objective was to determine the agreement between the anthropometric markers with respect to assessing obesity in adults with asthma.

METHODS

This cross-sectional study enrolled adult asthma patients attending an outpatient asthma clinic in southern Brazil. Patients were evaluated regarding sociodemographic data, lung function, asthma control, nutritional status and health-related quality of life (Asthma Quality of Life Questionnaire; AQLQ). Nutritional status was classified by body mass index (BMI), waist circumference (WC) and BF.

RESULTS

The mean (SD) age of the 198 patients was 56.2 (14.8) years. The prevalence of uncontrolled asthma among subjects who were overweight as diagnosed by their BMI was 64.6% higher than in those who were normal weight. An increase in a measure of BMI (1 kg m^-2 ) decreases approximately 44-59% of symptoms, activity limitations and emotional function domains of the AQLQ, whereas an increase in a measure in WC (1 cm) decreases approximately 24-30% of the same domains. Agreement between BMI and BF was 0.566 and that between BMI and WC was 0.597 by Kendall's Tau-b test.

CONCLUSIONS

The prevalence of uncontrolled asthma is greater in overweight subjects than in normal weight subjects. WC and BMI were negatively associated with symptoms, activity limitations and emotional function domains of the AQLQ. BMI appears to be sufficient to diagnose the nutritional status of subjects with asthma in this population.

Association of asthma diagnosis with leptin and adiponectin: a systematic review and meta-analysis

There is some evidence which shows that higher levels of serum leptin and lower levels of serum adiponectin are associated with the diagnosis of asthma. This meta-analysis evaluated the association of serum leptin and adiponectin levels with the diagnosis of asthma. We searched the MEDLINE, Cochrane, EMBASE and CINAHL Plus databases up to July 2015. Eligible studies were randomized controlled trials, prospective studies, retrospective studies, case-control studies and cohort studies. 13 studies with 3642 patients were included in the study. The meta-analysis found that in the overall study population, the diagnosis of asthma was associated with higher levels of leptin (pooled standardized difference in means=0.867, 95% CI 0.416 to 1.318, p<0.001) and lower levels of adiponectin (pooled standardized difference in means=-0.371, 95% CI -0.728 to -0.014, p=0.042) in patients with asthma compared with controls. Subgroup analysis found that higher leptin levels were associated with asthma both in adults (standardized difference in means=1.374, 95% CI 0.621 to 2.126, p<0.001) and children (standardized difference in means=0.302, 95% CI 0.010 to 0.594, p=0.042). However, borderline association of adiponectin with asthma was seen in adults (p=0.05), but not in children (p=0.509). Sensitivity analysis indicated that the findings for leptin were robust. Our findings are consistent with higher levels of serum leptin being associated with asthma regardless of age, and low adiponectin levels being associated with asthma in adults only.

Patient stratification and the unmet need in asthma

Asthma is often described as an inflammatory disease of the lungs and in most patients symptomatic treatment with bronchodilators or inhaled corticosteroids is sufficient to control disease. Unfortunately there are a proportion of patients who fail to achieve control despite treatment with the best current treatment. These severe asthma patients have been considered a homogeneous group of patients that represent the unmet therapeutic need in asthma. Many novel therapies have been tested in unselected asthma patients and the effects have often been disappointing, particularly for the highly specific monoclonal antibody-based drugs such as anti-IL-13 and anti-IL-5. More recently, it has become clear that asthma is a syndrome with many different disease drivers. Clinical trials of anti-IL-13 and anti-IL-5 have focused on biomarker-defined patient groups and these trials have driven the clinical progression of these drugs. Work on asthma phenotyping indicates that there is a group of asthma patients where T helper cell type 2 (Th2) cytokines and inflammation predominate and these type 2 high (T2-high) patients can be defined by biomarkers and response to therapies targeting this type of immunity, including anti-IL-5 and anti-IL-13. However, there is still a subset of T2-low patients that do not respond to these new therapies. This T2-low group will represent the new unmet medical need now that the T2-high-targeting therapies have made it to the market. This review will examine the current thinking on patient stratification in asthma and the identification of the T2-high subset. It will also look at the T2-low patients and examine what may be the drivers of disease in these patients.

Obesity risk class and asthma outpatient service utilization by the middle aged and elderly in Taiwan

BACKGROUND

According to the estimates of the World Health Organization (WHO), there were about 300 million people in the world suffering from asthma in 2005. Among the risk factors of asthma is obesity, which was found to be significantly associated with asthma in recent decades.

OBJECTIVES

In this study, we analyze the relationship between obesity risk class and asthma outpatient service utilization by the middle-aged and elderly in Taiwan.

METHODS

Adopting data from the 2005 Nation Health Interview Survey (NHIS) and National Health Insurance Research Database (NHIRD), we first utilize latent class analysis (LCA) to identify obesity risk classes. Next, we utilize a logit and a negative binominal model to analyze the relationship between each obesity risk class and asthma outpatient service utilization.

RESULTS

Results indicate that compared with the "overweight/obese with low consumption of vegetable/fruit and little exercise" class, the classes "normal-weight with high consumption of vegetable/fruit and moderate exercise" and "overweight/obese with high consumption of vegetable/fruit and moderate exercise" tend to have low probabilities and less number of visits of utilizing asthma outpatient services.

CONCLUSIONS

Our results may constitute useful references for clinicians and government policy makers formulating strategies for asthma management and prevention. Better informed strategies for asthma management could, in turn, increase the efficiency of asthmatic patients' care, which could provide efficient assistance to the target group based on the obesity risk classes.

Obese individuals experience wheezing without asthma but not asthma without wheezing: a Mendelian randomisation study of 85,437 adults from the Copenhagen General Population Study

BACKGROUND

Observational studies suggest that obesity is associated with increased risk of asthma. However, it is unknown whether this could be explained by wheezing. We tested the hypothesis that high body mass index (BMI) observationally and genetically is associated with high risk of wheezing and asthma, and that the association between high BMI and asthma is explained by wheezing.

METHODS

We genotyped 85,437 individuals aged 20-100 years from the Copenhagen General Population Study for FTO (rs9939609), MC4R (rs17782313), TMEM18 (rs6548238) GNPDA2 (rs10938397) and BDNF (rs10767664); 14,500 individuals experienced wheezing and 5406 had asthma. Wheezing was self-reported, and asthma was ascertained through self-report, hospital contacts with asthma, and/or receiving medication for asthma. BMI was calculated as measured weight divided by measured height squared (kg/m2).

RESULTS

In observational analyses versus BMI of 18.5-22.4 kg/m2, ORs for wheezing were 1.23 (95% CI 1.00 to 1.52) for BMI <18.5 kg/m2, 1.17 (1.10 to 1.25) for 22.5-24.9 kg/m2, 1.44 (1.35 to 1.54) for 25-27.4 kg/m2, 1.86 (1.73 to 1.99) for 27.5-29.9 kg/m2, 2.48 (2.31 to 2.66) for 30-34.9 kg/m(2), 3.86 (3.48 to 4.28) for 35-39.9 kg/m2 and 6.05 (5.12 to 7.14) for BMI ≥40 kg/m2. Corresponding ORs for asthma were 1.28 (0.95 to 1.74), 1.07 (0.97 to 1.17), 1.14 (1.04 to 1.25), 1.32 (1.20 to 1.46), 1.39 (1.25 to 1.54), 1.54 (1.31 to 1.81) and 1.99 (1.55 to 2.56), respectively. Compared with BMI allele score 0-4, scores 5, 6 and 7-10 were associated with 0.22, 0.51 and 0.76 kg/m2 higher BMI, respectively. Genetically determined ORs per unit higher BMI were 1.22 (1.15 to 1.31) for wheezing, 1.18 (1.10 to 1.27) for wheezing without asthma, 1.08 (0.98 to 1.19) for asthma, and 0.85 (0.73 to 0.99) for asthma without wheezing. Corresponding observational ORs were 1.09 (1.09 to 1.10), 1.09 (1.08 to 1.09), 1.03 (1.03 to 1.04) and 0.99 (0.98 to 1.00), respectively.

CONCLUSIONS

High BMI was associated with high risk of wheezing without asthma, but not with high risk of asthma without wheezing.

Alterations in Lung Functions Based on BMI and Body Fat % Among Obese Indian Population at National Capital Region

BACKGROUND

In India, non-asthmatic hospital admission case study has been conducted to find out the relationship between obesity and lung functions. The main objective of the present study was to find out the alterations in lung functions due to obesity among Indian population living at National Capital Region (NCR).

MATERIALS AND METHODS

We examined 609 non obese and 211 obese subjects in a cross sectional study from National Capital Region, India with age group ranges between 18-70 years. BMI and body fat % was determined using body fat analyzer. Obese and non-obese subjects were classified based on criteria for BMI and Body fat %. Lung function test viz., FEV1 and PEFR were conducted using portable spirometer (PIKO-1).

RESULTS

A significant correlation (p<0.05) was observed between BMI and PEFR among non-obese male and female subjects. Decline in PEFR and FEV1 values for corresponding increase in body fat % was observed among study subjects. A significant (p<0.01) decline in mean FEV1 and PEFR was observed among non-obese and obese subjects, compared to their Indian reference standards for lung functions. A significant negative correlation (p<0.01) was observed between body fat % and lung functions (FEV1, PEFR).

CONCLUSION

It is concluded that obese subjects are at a risk of lung function impairment, based on the criteria followed for BMI and body fat %. The study also demonstrate that body fat% classification as a better index for determination of obese subjects compared to BMI classification, with respect to lung function impairments.

Piecewise Mixed Effects Model to Compare the Weight-gain Patter ns Before and After Diagnosis of Asthma in Children Younger than 5 Years

Asthma and obesity are two significant public health problems that both originate in early childhood and have shared risk factors and manifestations. Studies suggest a strong association between asthma development and subsequent accelerated weight gain. Children are diagnosed with asthma in early childhood and are often exposed to factors associated with rapid weight gain. This article intends to demonstrate an innovative application of the piecewise mixed effects model to characterize the difference in the temporal rate of change in BMIz, the standardized scores of body mass index and weight-for-length that measure weight status, before and after asthma diagnosis in children younger than 5 years. The data consist of unique sequences from 1194 children's clinic visits during the first 5 years of life. We used a knot at the time of diagnosis and detected a differential weight-gain pattern before and after asthma diagnosis. The pre- and post-asthma-diagnosis weight-gain patterns further differ by sex and race-ethnicity. After asthma diagnosis, female children showed a higher increase in the rate of change in BMIz than males. Non-Hispanic African Americans and Hispanics had higher post-diagnosis rates of change in BMIz than Caucasians. The differential weight-gain patterns between male and female children were mainly contributed by Caucasian children. These findings could have important implications in the clinical care of children after asthma diagnosis.

Abdominal and general adiposity and level of asthma control in adults with uncontrolled asthma

RATIONALE

Abdominal adiposity may be an important risk factor for uncontrolled asthma in adults, controlling for general obesity. Whether the relationship, if present, is explained by other factors (e.g., asthma onset age, sex, and/or coexisting conditions) is unclear.

OBJECTIVES

To examine whether clinically applicable anthropometric measures of abdominal adiposity--waist circumference and waist-to-height ratio (WHtR)--are related to poorer asthma control in adults with uncontrolled asthma controlling for body mass index (BMI), and whether the relationship (if present) is explained by gastroesophageal reflux disorder (GERD), sleep quality, or obstructive sleep apnea (OSA) or differs by age of asthma onset or sex.

METHODS

Patients aged 18 to 70 years with uncontrolled asthma (n = 90) participated in a 6-month randomized clinical trial.

MEASUREMENTS AND MAIN RESULTS

Baseline measures included sociodemographics, standardized anthropometrics, Asthma Control Test (ACT), GERD Symptom Assessment Scale, Pittsburgh Sleep Quality Index, and Berlin Questionnaire for Sleep Apnea. Participants (mean [SD] age, 52 [12] yr) were racially and ethnically diverse, 67% women, and 69% overweight or obese, and 71% reported their age of asthma onset was 12 years or older. Participants had uncontrolled asthma (mean [SD] ACT score, 14.9 [3.7]) and low GERD symptoms score (0.6 [0.4]); 67% reported poor sleep quality, and 42% had a high OSA risk. General linear regression results showed that worse ACT scores were significantly associated with every SD increase in waist circumference (β = -1.03; 95% confidence interval [CI], -1.96 to -0.16; P = 0.02) and waist-to-height ratio (β = -1.16; 95% CI, -2.00 to -0.33; P = 0.008), controlling for sociodemographics. Waist-to-height ratio remained correlated with ACT (β = -2.30; 95% CI, -4.16 to -0.45; P = 0.02) after further adjusting for BMI. The BMI-controlled relationship between WHtR and ACT did not differ by age of asthma onset or sex (P > 0.05 for interactions) and persisted after additional adjustment for GERD, sleep quality, or OSA scores. Poor sleep quality was associated with worse ACT scores (β = -0.87; 95% CI, -1.71 to -0.03; P = 0.045) controlling for waist-to-height ratio, BMI, and sociodemographics.

CONCLUSIONS

Abdominal adiposity by waist-to-height ratio and poor sleep quality correlated with poorer asthma control in adults with uncontrolled asthma, after controlling for BMI and sociodemographics. These results warrant replication in larger studies of diverse populations. Clinical trial registered with www.clinicaltrials.gov (NCT 01725945).

Pathway from central obesity to childhood asthma. Physical fitness and sedentary time are leading factors

RATIONALE

Available prospective studies of obesity and asthma have used only body mass index (BMI) as an indicator for adiposity; studies using detailed obesity measures are lacking, and the role of physical fitness level and sedentary time remains unexplored in the link between obesity and asthma.

OBJECTIVES

To compare various anthropometric measures of obesity in relation to childhood asthma, and to further characterize the interrelations among central obesity, physical fitness level, sedentary time, and asthma.

METHODS

The nationwide Taiwan Children Health Study followed 2,758 schoolchildren from fourth to sixth grade, annually collecting data regarding physical fitness, sedentary time, obesity measures (comprising body weight and height, abdominal and hip circumference, skin fold thickness, and body composition), asthma, and pulmonary function tests. The generalized estimating equation was used for 3 years of repeated measurements to analyze the interrelation among obesity, sedentary time, physical fitness level, and asthma; a structural equation model was used to explore the pathogenesis among these factors. Asthma incidence was analyzed during a 2-year follow-up among centrally obese and nonobese groups in baseline children without asthma.

MEASUREMENTS AND MAIN RESULTS

Central obesity most accurately predicts asthma. Low physical fitness levels and high screen time increase the risk of central obesity, which leads to asthma development. Obesity-related reduction in pulmonary function is a possible mechanism in the pathway from central obesity to asthma.

CONCLUSIONS

Central obesity measures should be incorporated in childhood asthma risk predictions. Children are encouraged to increase their physical fitness levels and reduce their sedentary time to prevent central obesity-related asthma.

Interaction of metabolic syndrome with asthma in postmenopausal women: role of adipokines

The increasing prevalence of both asthma and obesity are major health problems. Recent studies established a possible link between obesity and asthma; however, the underlying mechanism is not clear. The aim of the study was to analyze the prevalence of metabolic syndrome in postmenopausal subjects with asthma and search the interactions between adipokines, metabolic syndrome, and asthma. A total of 45 female patients (57.5 ± 13.9 years) with asthma and 30 healthy subjects (59.6 ± 12.8 years) in postmenopausal status were enrolled in this study. For the diagnosis of metabolic syndrome, modified World Health Organization diagnostic criteria were used. Blood levels of glucose, lipid profile, HbA1c, insulin, CRP, leptin, adiponectin, tumor necrosis factor-alpha, interleukin (IL)-6, IL-8 and plasminogen activator inhibitor-1 (PAI-1) were measured. The mean body mass index was 29.6 ± 5.4 for asthma patients and 28.2 ± 5.3 for the control group. The incidence of metabolic syndrome was found as 26 % for both groups. Insulin resistance as calculated by homeostasis model assessment (HOMA-IR) and fasting insulin levels were significantly higher in asthma patients (p < 0.001 for both parameters). Leptin levels were significantly higher (p = 0.001) and adiponectin levels were lower (p = 0.029) in asthma patients compared to controls. We concluded that although incidence of obesity and metabolic syndrome was not higher in postmenopausal asthma patients than controls, there was an impairment of glucose metabolism and altered adipokine levels in asthma patients.

Association of Body Mass Index (BMI) with Lung Function Parameters in Non-asthmatics Identified by Spirometric Protocols

INTRODUCTION

Association between obesity and asthma has been reported widely, with disparity between males and females. Epidemiological data which indicate that obesity precedes development of asthma and increases the prevalence and incidence of asthma, raises the possibility of a causal association.

AIM

To find out the association, including gender differences, between Body Mass Index (BMI) and lung functions in non-asthmatics identified by spirometric protocols.

METHODS

A retrospective analysis was conducted of the spirometry results obtained between October 2012 and March 2013 for six months. Participants were referred by a variety of medical specialties to the pulmonary function laboratory in Physiology department, R.G. Kar Medical College, Kolkata, India of the 590 test results recorded in the study database 424 non-asthmatic subjects were reviewed.

RESULTS

Significant differences in the spirometric parameters, measured as a percentage of predicted were evident between male and female. Among obese subjects significant correlation is found between BMI and pulmonary function values, FEV1(r = -0.531, p=0.009); FEF25-75% (r= -0.653, p=0.001); FEV1/FVC (r= - 0.603, p=0.002). Significant association was found between BMI and lung function in obese female but not in obese male.

CONCLUSION

Association was found between indices of spirometry and BMI in non-asthmatic obese group along with a gender disparity.

Prevalence of obesity in asthma and its relations with asthma severity and control

OBJECTIVE: To determine the prevalence of obesity in asthmatic patients attending at an outpatient clinic, and to investigate its relationships with asthma severity and level of asthma control. METHODS: In a cross-sectional study we recruited patients aged 11 years and older with confirmed asthma diagnosis from the outpatient asthma clinic of Hospital de Clínicas de Porto Alegre, Brazil. They underwent an evaluation by a general questionnaire, an asthma control questionnaire and by pulmonary function tests. Nutritional status was classified by body mass index (BMI). RESULTS: 272 patients were included in the study. Mean age was 51.1 ± 16.5 years and there were 206 (74.9%) female patients. Mean BMI was 27.5 ± 5.3 kg/m², and 96 (35.3%) patients were classified as normal weight, 97 (35.7%) as overweight and 79 (29%) as obesity. There was a significant higher proportion of female than male patients (34.3% vs. 13.2%, p = 0.002) in the obesity group. There were no significant differences with respect to asthma control (p = 0.741) and severity classification (p = 0.506). The FEV1% predicted was significantly higher in the obese than in the non-obese group (73.7% vs. 67.2%, p = 0.037). Logistic regression analysis identified sex (OR = 3.84, p = 0.002) as an independent factor associated with obesity. CONCLUSIONS: This study showed a high prevalence of obesity in asthmatic patients. Obese and non-obese subjects were similar in regard to asthma severity and level of asthma control. Female sex was associated with obesity in this asthma population.

Prevalence of obesity in asthma and its relations with asthma severity and control

OBJECTIVE

To determine the prevalence of obesity in asthmatic patients attending at an outpatient clinic, and to investigate its relationships with asthma severity and level of asthma control.

METHODS

In a cross-sectional study we recruited patients aged 11 years and older with confirmed asthma diagnosis from the outpatient asthma clinic of Hospital de Clínicas de Porto Alegre, Brazil. They underwent an evaluation by a general questionnaire, an asthma control questionnaire and by pulmonary function tests. Nutritional status was classified by body mass index (BMI).

RESULTS

272 patients were included in the study. Mean age was 51.1 ± 16.5 years and there were 206 (74.9%) female patients. Mean BMI was 27.5 ± 5.3kg/m(2), and 96 (35.3%) patients were classified as normal weight, 97 (35.7%) as overweight and 79 (29%) as obesity. There was a significant higher proportion of female than male patients (34.3% vs. 13.2%, p = 0.002) in the obesity group. There were no significant differences with respect to asthma control (p = 0.741) and severity classification (p = 0.506). The FEV1% predicted was significantly higher in the obese than in the non-obese group (73.7% vs. 67.2%, p = 0.037). Logistic regression analysis identified sex (OR = 3.84, p = 0.002) as an independent factor associated with obesity.

CONCLUSIONS

This study showed a high prevalence of obesity in asthmatic patients. Obese and non-obese subjects were similar in regard to asthma severity and level of asthma control. Female sex was associated with obesity in this asthma population.

Obesity and asthma: physiological perspective

Obesity induces some pertinent physiological changes which are conducive to either development of asthma or cause of poorly controlled asthma state. Obesity related mechanical stress forces induced by abdominal and thoracic fat generate stiffening of the lungs and diaphragmatic movements to result in reduction of resting lung volumes such as functional residual capacity (FRC). Reduced FRC is primarily an outcome of decreased expiratory reserve volume, which pushes the tidal breathing more towards smaller high resistance airways, and consequentially results in expiratory flow limitation during normal breathing in obesity. Reduced FRC also induces plastic alteration in the small collapsible airways, which may generate smooth muscle contraction resulting in increased small airway resistance, which, however, is not picked up by spirometric lung volumes. There is also a possibility that chronically reduced FRC may generate permanent adaptation in the very small airways; therefore, the airway calibres may not change despite weight reduction. Obesity may also induce bronchodilator reversibility and diurnal lung functional variability. Obesity is also associated with airway hyperresponsiveness; however, the mechanism of this is not clear. Thus, obesity has effects on lung function that can generate respiratory distress similar to asthma and may also exaggerate the effects of preexisting asthma.

Role of obesity in asthma control, the obesity-asthma phenotype

Asthma is a disease with distinct phenotypes that have implications for both prognosis and therapy. Epidemiologic studies have demonstrated an association between asthma and obesity. Further studies have shown that obese asthmatics have poor asthma control and more severe asthma. This obese-asthma group may represent a unique phenotype. The mechanisms behind poor asthma control in obese subjects remain unclear, but recent research has focused on adipokines and their effects on the airways as well as the role of oxidative stress. Both surgical and nonsurgical weight loss therapy have shown promising results with improvements in asthma control and decreased asthma severity. Comorbid conditions such as gastroesophageal reflux disease and obstructive sleep apnea may also have a role in poor asthma control in obese asthmatics. Further research is needed to define the mechanisms behind this phenotype which will guide the development of targeted therapies.

A systematic review of the association between obesity and asthma in children

AIM

To provide a comprehensive integration of contemporary studies focusing on the relationship between obesity and asthma in paediatric populations.

BACKGROUND

The simultaneous increase in asthma and obesity prevalence has been widely discussed over the past 20 years. Although studies have discovered a positive correlation between the two, evidence-based findings are needed to develop nursing interventions.

DESIGN

A quantitative systematic review on the literature was conducted from June-December 2011.

DATA SOURCES

An electronic database search was conducted for studies published between January 1966-May 2011. Additional articles were identified through the reference lists of reviewed papers.

REVIEW METHODS

Inclusion/exclusion criteria and quality appraisal were applied to ensure research primarily designed to study the relationship between obesity and asthma in children was included.

RESULTS

The majority of studies support a positive association between obesity and asthma in children. Among correlates recognized as important effect modifiers, gender was the most prominent, with obese girls more likely to have asthma diagnoses than obese boys. Scrutinization of covariates in selected studies revealed that most related to children's demographic characteristics and were inconsistent across the studies.

CONCLUSIONS

This review was designed to integrate contemporary scientific findings on the association between obesity and asthma by including a large number of studies with variant research designs. To identify high-risk groups and develop nursing interventions to help children affected by both epidemics, more interdisciplinary and well-designed investigations focusing on an expanded spectrum of correlates including demographic and behavioural factors are warranted.

Exploring the obesity-asthma link: do all types of adiposity increase the risk of asthma?

BACKGROUND

Obesity and risk of asthma are linked. Different distributions of adiposity, such as visceral, subcutaneous or ectopic adiposity, may affect asthma risk differently.

OBJECTIVE

To explore the association of different adiposity types with self-reported asthma, bronchial inflammation and lung function, accounting for possible effect modifiers, such as atopy and gender.

METHODS

In a general population sample of 3471 persons aged 19-72, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were measured by ultrasound, and fat percentage by bio-impedance. Body mass index, waist circumference, waist-to-hip ratio (WHR), bronchial inflammation as fractional expiratory nitric oxide (FeNO), lung function [FEV(1) and forced vital capacity (FVC)], and atopy (specific IgE) were measured.

RESULTS

All adiposity measures were associated with a higher risk of asthma. The risk estimates (odds ratios, OR, with 95% confidence interval, CI) of current asthma were of similar magnitude for all six adiposity measures ranging between 1.17, CI = 0.98-1.40 (SAT) and 1.51, CI = 1.17-1.95 (WHR). The adiposity-asthma associations were significantly stronger in non-atopics than in atopics. In non-atopics the risk estimates of current asthma ranged between 1.35 CI = 1.08-1.72 and 1.82 CI = 1.34-2.46 for SAT and WHR respectively. Consistent results were obtained using dichothomized adiposity measures (obese vs. non-obsese). The FVC and FEV(1) decreased significantly with increasing adiposity in both atopics and non-atopics, e.g. FVC decreased between 36 mL (CI = 10, 62 mL) and 155 mL (CI = 124, 186 mL) for one unit (standard error) increase of SAT and VAT respectively. Adiposity measures were not associated with atopy and not consistently associated with FeNO levels.

CONCLUSIONS AND CLINICAL RELEVANCE

The effect of adiposity on asthma was mainly seen in non-atopics and did not appear to depend on the distribution of adiposity as reflected by the adiposity measures used in the present study. Increasing adiposity was associated with lower lung function independent of atopic status.

Sex Differences in the Effects of Inhaled Corticosteroids on Weight Gain among Patients with Asthma

Background. Studies have shown that asthma and asthma exacerbations are related to body weight and that this relationship might be sex-specific. While oral corticosteroids have been associated with weight gain, little is known about the effect of inhaled corticosteroid (ICS) use on short-term weight gain. The purpose of the present study was to examine whether ICSs would be associated with weight gain among asthmatic patients. Methods. A total of 180 adult patients with physician-diagnosed asthma provided details of their medical history and demographic information, along with height and weight at baseline and at one year. Weight change was defined as follow-up minus baseline weight. General linear models were used to assess the relationship between ICS dose (fluticasone propionate equivalent) and sex. Results. Significant main effects of sex (P=.005) and ICS dose (P=.036) and an interaction effect of sex and ICS dose (P=.003) on weight change were observed. Further analysis of the interaction indicated that women had greater weight gain, while men had decreased weight with increased ICS dose. Conclusions. Findings suggest that ICSs may trigger weight gain in females and highlight the need for studies to confirm this relationship and examine the potential underlying mechanisms.

The Saskatchewan rural health study: an application of a population health framework to understand respiratory health outcomes

Background

Respiratory disease can impose a significant burden on the health of rural populations. The Saskatchewan Rural Health Study (SRHS) is a new large prospective cohort study of ages 6 and over currently being conducted in farming and non-farming communities to evaluate potential health determinants associated with respiratory outcomes in rural populations. In this article, we describe the rationale and methodology for the adult component.

The study is being conducted over 5 years (2009–15) in two phases, baseline and longitudinal. The baseline survey consists of two components, adults and children. The adult component consists of a questionnaire-based evaluation of individual and contextual factors of importance to respiratory health in two sub populations (a Farm Cohort and a Small Town Cohort) of rural families in Saskatchewan Rural Municipalities (RMs). Clinical studies of lung function and allergy tests are being conducted on selected sub-samples of the two cohorts based on the positive response to the last question on the baseline questionnaire: “Would you be willing to be contacted about having breathing and/or allergy tests at a nearby location?”. We adopted existing population health theory to evaluate individual factors, contextual factors, and principal covariates on the outcomes of chronic bronchitis, chronic obstructive pulmonary disease, asthma and obstructive sleep apnea.

Findings

Of the RMs selected to participate, 32 (89%) out of 36 RMs and 15 (94%) out of 16 small towns within the RMs agreed to participate. Using the mail out survey method developed by Dillman, we obtained completed questionnaires from 4264 households (8261 individuals). We obtained lung function measurements on 1609 adults, allergy skin test information on 1615 adults; both measurements were available on 1549 adults. We observed differences between farm and non-farm rural residents with respect to individual, contextual factors and covariates.

Discussion

There are differences between farm and non-farm rural residents with respect to individual and contextual factors and other variables of importance. The findings of the SRHS will improve knowledge of respiratory disease etiology, assist in the development and targeting of prevention programs, and in planning health services with farm and small town populations.

Pulmonary function in adults with recent and former asthma and the role of sex and atopy

Background

Pulmonary function is not fully reversible in asthma in children and may continue into adult life. This study was to determine the association between asthma and reduced pulmonary function in adults and the modification by sex and atopic status.

Methods

A cross-sectional study of 1492 adults aged 18 years or over was conducted in a rural community. Atopy, height, weight, waist circumference (WC) and pulmonary function were measured. Participants with ever asthma were those who reported by questionnaire a history of asthma diagnosed by a physician during lifetime. Participants who had former (only) asthma were those who reported having physician-diagnosed asthma more than 12 months ago. Participants who had recent asthma were those who reported having asthma during the last 12 months.

Results

Men had higher values of forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁) compared with women, but FEV₁/FVC ratio showed no significant difference between sexes. Atopic status was not related to pulmonary function and the average values of the pulmonary function testing variables were almost the same for non-atopic and atopic individuals. Individuals with ever, recent or former asthma had significant lower values of FEV₁ and FEV₁/FVC ratio than those who reported having no asthma, and the associations tended to be stronger in men than in women. The interaction between atopy and asthma was not statistically significant.

Conclusions

Adults who reported having recent asthma or former asthma had reduced pulmonary function, which was significantly modified by sex but not by atopic status.

Abdominal adiposity and obstructive airway disease: testing insulin resistance and sleep disordered breathing mechanisms

BACKGROUND

This study examined associations of abdominal adiposity with lung function, asthma symptoms and current doctor-diagnosed asthma and mediation by insulin resistance (IR) and sleep disordered breathing (SDB).

METHODS

A random sample of 2500 households was drawn from the community of Whyalla, South Australia (The Whyalla Intergenerational Study of Health, WISH February 2008 - July 2009). Seven-hundred twenty-two randomly selected adults (≥18 years) completed clinical protocols (32.2% response rate). Lung function was measured by spirometry. Post-bronchodilator FEV1/FVC was used to measure airway obstruction and reversibility of FEV1 was calculated. Current asthma was defined by self-reported doctor-diagnosis and evidence of currently active asthma. Symptom scores for asthma (CASS) and SDB were calculated. Intra-abdominal fat (IAF) was estimated using dual-energy x-ray absorptiometry (DXA). IR was calculated from fasting glucose and insulin concentrations.

RESULTS

The prevalence of current doctor-diagnosed asthma was 19.9% (95% CI 16.7 - 23.5%). The ratio of observed to expected cases given the age and sex distribution of the population was 2.4 (95%CI 2.1, 2.9). IAF was not associated with current doctor-diagnosed asthma, FEV1/FVC or FEV1 reversibility in men or women but was positively associated with CASS independent of IR and SDB in women. A 1% increase in IAF was associated with decreases of 12 mL and 20 mL in FEV1 and FVC respectively in men, and 4 mL and 7 mL respectively in women. SDB mediated 12% and 26% of these associations respectively in men but had minimal effects in women.

CONCLUSIONS

In this population with an excess of doctor-diagnosed asthma, IAF was not a major factor in airway obstruction or doctor-diagnosed asthma, although women with higher IAF perceived more severe asthma symptoms which did not correlate with lower FEV1. Higher IAF was significantly associated with lower FEV1 and FVC and in men SDB mechanisms may contribute up to one quarter of this association.

Predictors of respiratory symptoms in a rural Canadian population: A longitudinal study of respiratory health

BACKGROUND

Predictors of new and long-term respiratory symptoms for rural residents are not well defined.

OBJECTIVE

To identify early predictors of respiratory symptoms in a rural community population.

METHODS

The study population consisted of 871 adults living in the rural community of Humboldt, Saskatchewan, who participated in two cross-sectional respiratory studies conducted in 1993 and 2003. Questionnaire information obtained at both time points included respiratory symptoms (cough, phlegm and wheeze), history of allergy, smoking, and information regarding home and farm environments. Transitional modelling, in which measurement in a longitudinal sequence is described as a function of previous outcomes, was used to predict later outcomes of cough, phlegm and wheeze. Asymptomatic individuals in 1993 were assessed to determine factors associated with the development of symptoms during the study period.

RESULTS

The prevalences of cough, phlegm and wheeze in 1993 were 16.1%, 18.1% and 25.5%, respectively. Change in symptoms over time was significant for cough, phlegm and wheeze. The adjusted ORs (95% CI) from separate transitional models for each respiratory outcome in 1993 that predicted the same symptom in 2003 were 6.32 (4.02 to 9.95) for cough, 14.36 (9.01 to 22.89) for phlegm and 6.40 (4.40 to 9.32) for wheeze. For asymptomatic individuals in 1993, home dampness, allergic reaction to inhaled allergens and cigarette smoking were major risk factors associated with respiratory symptoms that were reported in 2003.

CONCLUSION

The presence of previous respiratory symptoms, allergies and environmental exposures can predict the occurrence of future respiratory symptoms in adults.

Abdominal obesity and late-onset asthma: cross-sectional and longitudinal results: the 3C study

Whereas global obesity assessed by BMI has been related to asthma risk, little is known as to the potential implication of abdominal adiposity in this relationship. In the elderly, in whom asthma remains poorly studied, abdominal adiposity tends to increase at the expense of muscle mass. The purpose of this study was to investigate the association between abdominal adiposity, assessed by waist circumference (WC), and prevalence and incidence of asthma in a large elderly cohort. Cross-sectional analysis was based on 7,643 participants aged ≥65 years including 592 (7.7%) with lifetime physician-diagnosed asthma. Longitudinal analysis involved 6,267 baseline nonasthmatics followed-up for a period of 4 years, 67 of whom exhibited incident asthma. Baseline WC was categorized according to sex-specific criteria (men/women): <94/80 cm (reference), [94-102[/[80-88[ (abdominal overweight), and ≥102/88 (abdominal obesity). Logistic and Cox regression models estimated asthma risk associated with WC after adjustment for age, sex, educational level, smoking status, BMI, physical ability, dyspnea, chronic bronchitis symptoms and history of cardiovascular disease. At baseline, asthma risk increased with increasing WC independently of BMI and other confounders (adjusted odds ratio (ORa), 95% confidence interval (CI): 1.30, 1.02-1.65 and ORa: 1.76, 1.31-2.36 for abdominal overweight and obesity, respectively). Asthma incidence was related to WC (hazard ratio (HRa), 95% CI: 2.69, 1.21-5.98 and HRa: 3.84, 1.55-9.49, for abdominal overweight and obesity, respectively). Estimates were similar in both sexes. In the elderly, abdominal adiposity was independently associated with increased prevalence and incidence of asthma. Studies aiming to understand the mechanisms involved in the adiposity-asthma link are needed.

Body mass index is related with bronchial function and reversibility in children with allergic rhinitis and asthma

Several studies have outlined a possible relationship between an increased body mass index and respiratory allergic diseases, such as asthma and rhinitis.The aim of the study was to analyse the relationship between BMI and lung function, including bronchodilation test, in allergic children. The study included 153 children (103 males, mean age 12.8 years) with allergic rhinitis and mild asthma. All subjects were evaluated performing skin prick test, spirometry, and bronchodilalation test. BMI values were in the normal range as well as lung function. BMI significantly related with FEV1, FVC values and FEV1/FVC ratio both before and after bronchodilation. In conclusion, this study provides the first evidence that BMI is negatively related with bronchial reversibility in children with allergic rhinitis and asthma.As reversibility is related with bronchial inflammation, this finding might underline a link between overweight and allergic inflammation.

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.

Respiratory complications of obesity

Obesity, well known as a cardiovascular risk factor, can also lead to significant respiratory complications. The respiratory changes associated with obesity extend from a simple change in respiratory function, with no effect on gas exchange, to the more serious condition of hypercapnic respiratory failure, characteristic of obesity hypoventilation syndrome. More recently, it has been reported that there is an increased prevalence of asthma which is probably multifactorial in origin, but in which inflammation may play an important role. Hypoventilation in the obese subject is the result of complex interactions that involve changes in the ventilatory mechanics and anomalies in breathing control. Two other conditions (COPD and sleep apnea-hypopnea syndrome [SAHS], often present in obese patients, can trigger or aggravate it. The prevalence of hypoventilation in the obese is under-estimated and the diagnosis is usually established during an exacerbation, or when the patient is studied due to suspicion of SAHS. Ventilatory management of these patients includes either CPAP or NIV. The choice of one or another will depend on the underlying clinical condition and whether or not there is another comorbidity. Both NIV and CPAP have demonstrated their effectiveness, not only in the control of gas exchange, but also in improving the quality of life and survival of these patients.

Obesity and poor asthma control in patients with severe asthma

BACKGROUND

Asthma is a public health problem as it leads to hospitalization and eventual death, particularly in its severe forms. Many studies have demonstrated an association between obesity and asthma.

OBJECTIVE

The aim of this study was to investigate the relationship between obesity and asthma control in a group of patients at a reference center for severe asthma in Brazil.

METHODS

This cross-sectional study was conducted in the outpatient central reference clinic of the Program for Control of Asthma in the State of Bahia. It included 508 subjects with severe asthma of both genders and above 18 years of age. All the participants answered a sociodemographic and a clinical questionnaire to collect information on their asthma and comorbidities, such as rhinitis and gastro-esophageal reflux disease (GERD). Participants also completed the Asthma Control Questionnaire, performed a spirometry test, and had their weight, height, and waist and hip circumferences registered.

RESULTS

Logistic regression analysis demonstrated a positive association between body mass index (BMI) and uncontrolled asthma [odds ratio (OR) 1.5; 95% confidence interval (CI) 1.02-2.20]. Symptoms of chronic rhinitis and GERD were also significantly associated with uncontrolled asthma (OR 3.68, 95% CI 1.50-9.01; and OR 2.78, 95% CI 1.91-4.03, respectively). There was no correlation between waist-to-hip ratios and asthma control.

CONCLUSION

In our sample of patients with severe asthma, those who were obese were more likely to have uncontrolled asthma than patients with a normal BMI. Nevertheless, this is not conclusive evidence for a direct causal association between obesity and poor asthma control. Future studies are necessary to dissect the relationship between obesity and asthma outcomes.

Variations in BMI and prevalence of health risks in diverse racial and ethnic populations

When examining health risks associated with the BMI, investigators often rely on the customary BMI thresholds of the 1995 World Health Organization report. However, within-interval variations in morbidity and mortality can be substantial, and the thresholds do not necessarily correspond to identifiable risk increases. Comparing the prevalence of hypertension, diabetes, coronary heart disease (CHD), asthma, and arthritis among non-Hispanic whites, blacks, East Asians and Hispanics, we examine differences in the BMI-health-risk relationships for small BMI increments. The analysis is based on 11 years of data of the National Health Interview Survey (NHIS), with a sample size of 337,375 for the combined 1997-2007 Sample Adult. The analysis uses multivariate logistic regression models, employing a nonparametric approach to modeling the BMI-health-risk relationship, while relying on narrowly defined BMI categories. Rising BMI levels are associated with higher levels of chronic disease burdens in four major racial and ethnic groups, even after adjusting for many socio-demographic characteristics and three important health-related behaviors (smoking, physical activity, alcohol consumption). For all population groups, except East Asians, a modestly higher disease risk was noted for persons with a BMI <20 compared with persons with BMI in the range of 20-21. Using five chronic conditions as risk criteria, a categorization of the BMI into normal weight, overweight, or obesity appears arbitrary. Although the prevalence of disease risks differs among racial and ethnic groups regardless of BMI levels, the evidence presented here does not support the notion that the BMI-health-risk profile of East Asians and others warrants race-specific BMI cutoff points.

Role of age at asthma diagnosis in the asthma-obesity relationship

OBJECTIVE

To determine whether age at asthma diagnosis has an impact on the previously described relationship between asthma and obesity.

METHODS

Data were provided from Cycle 1.1 (2000⁄2001) of the Canadian Community Health Survey, a nationally representative health survey that included 6871 participants (2464 males and 4407 females) with asthma. Body mass index was used to categorize participants as normal weight (18.5 kg/m2 to 24.9 kg/m2), overweight (25 kg/m2 to 29.9 kg/m2) or obese (30 kg/m2 or greater). Multivariate logistic regression analyses were used to estimate the odds of overweight and obesity by self-reported age at asthma diagnosis, after accounting for current age and other covariables.

RESULTS

In fully adjusted models, males diagnosed with asthma during adolescence (12 to 20 years of age) were at elevated odds of obesity (OR 1.58; 95% CI 1.03 to 2.43) compared with asthmatic patients diagnosed during childhood (0 to 11 years of age). Women diagnosed with asthma in mid life (21 to 44 years of age) and later life (45 to 64 years of age) were 43% (OR 1.43; 95% CI 1.08 to 1.90) and 56% (OR 1.56; 95% CI 1.00 to 2.44) more likely to be obese than those diagnosed in childhood, respectively.

CONCLUSIONS

The impact of age at asthma diagnosis on the asthma-obesity relationship differed between males and females. However, the identification of high-risk groups of asthmatic patients may strengthen primary prevention strategies for obesity and related comorbidities at multiple levels of influence.

Asthma control, adiposity, and adipokines among inner-city adolescents

BACKGROUND

There is an association between adiposity and asthma prevalence, but the relationship to asthma control is unclear.

OBJECTIVES

We sought to understand the relationships among adiposity, sex, and asthma control in inner-city adolescents with asthma.

METHODS

We prospectively followed 368 adolescents with moderate-to-severe asthma (ages 12-20 years) living in 10 urban areas for 1 year. Asthma symptoms and exacerbations were recorded, and pulmonary function and exhaled nitric oxide levels were measured every 6 weeks. Adiposity measures (body mass index [BMI] and dual-energy X-ray absorptiometric scans) were made, and blood was collected for measurement of allergy markers, adiponectin, leptin, TNF-alpha, IL-6, and C-reactive protein levels.

RESULTS

More than 60% of female subjects and 50% of male subjects were above the 85th percentile of BMI for age. Higher BMI was associated with more symptom days (R = 0.18, P = .02) and exacerbations (R = 0.18, P = .06) among female subjects only. Adiponectin was inversely related to asthma symptoms (R = -0.18, P < .05) and exacerbations (R = -0.20, P < .05) and positively with FEV(1)/forced vital capacity ratio (R = 0.15, P < .05) in male subjects only independent of body size. There was no relationship between adiposity or adipokines and total IgE levels, blood eosinophil counts, and exhaled nitric oxide levels. Dual-energy X-ray absorptiometry provided little additional value in relating adiposity to asthma outcome in this population of adolescents.

CONCLUSION

Adiposity is associated with poorer asthma control in female subjects. Adiponectin is associated with improved asthma control in male subjects.

Body mass index and response to asthma therapy: fluticasone propionate/salmeterol versus montelukast

We studied the relationship between body mass index (BMI) on responses to asthma therapy using a retrospective analysis of four previously reported clinical trials. Fluticasone propionate (FP)/salmeterol via Diskus 100/50 microg twice daily and montelukast (MON) 10 mg daily were compared. BMI was classified as underweight (less than 20 kg/m(2)), normal (20-24.9 kg/m(2)), overweight (25-29.9 kg/m(2)), obese-1 (30-34.9 kg/m(2)), obese-2 (35-39.9 kg/m(2)), or obese-3 (at least 40 kg/m(2)). Outcomes assessed included forced expiratory volume in one second (FEV(1)), asthma symptom score, and albuterol use. FP/salmeterol produced greater improvements compared to MON in each of the asthma outcomes studied over the entire BMI range at the week-12 endpoint, with statistically significant differences noted among normal, overweight, obese-1, and obese-3 subjects. The within-treatment responses to FP/salmeterol across BMI ranges at the week-12 endpoint was statistically significantly greater in normal compared to obese-3 for FEV(1) and albuterol use, and in overweight compared to the obese-3 for each outcome studied. The within-treatment comparisons of MON across BMI ranges were significant for albuterol use in normal and underweight compared to obese-3 at the week-12 endpoint. Compared to subjects with normal BMI, the onset to peak FEV(1) may require longer treatment exposure in the very obese. Treatment responses to FP/salmeterol were consistently greater compared to MON and persisted at higher BMI.

Obesity, waist size and prevalence of current asthma in the California Teachers Study cohort

BACKGROUND

Obesity is a risk factor for asthma, particularly in women, but few cohort studies have evaluated abdominal obesity which reflects metabolic differences in visceral fat known to influence systemic inflammation. A study was undertaken to examine the relationship between the prevalence of asthma and measures of abdominal obesity and adult weight gain in addition to body mass index (BMI) in a large cohort of female teachers.

METHODS

Prevalence odds ratios (ORs) for current asthma were calculated using multivariable linear modelling, adjusting for age, smoking and race/ethnicity.

RESULTS

Of the 88 304 women in the analyses, 13% (n = 11,500) were obese (BMI > or = 30 kg/m(2)) at baseline; 1334 were extremely obese (BMI > or = 40 kg/m(2)). Compared with those of normal weight, the adjusted OR for adult-onset asthma increased from 1.40 (95% confidence interval (CI) 1.31 to 1.49) for overweight women to 3.30 (95% CI 2.85 to 3.82) for extremely obese women. Large waist circumference (>88 cm) was associated with increased asthma prevalence, even among women with a normal BMI (OR 1.37, 95% CI 1.18 to 1.59). Among obese women the OR for asthma was greater in those who were also abdominally obese than in women whose waist was < or = 88 cm (2.36 vs 1.57). Obese and overweight women were at greater risk of severe asthma episodes, measured by urgent medical visits and hospital admissions.

CONCLUSIONS

This study confirms the association between excess weight and asthma severity and prevalence, and showed that a large waist was associated with increased asthma prevalence even among women considered to have normal body weight.

Association of the TLR4 Asp299Gly polymorphism with lung function in relation to body mass index

Background

Previous studies have shown conflicting results for the association between TLR4 polymorphism (Asp299Gly) and lung function. We investigated the influence of TLR4 Asp299Gly, a polymorphism, on lung function in a community population.

Methods

In 2003, a cross-sectional survey was conducted to assess the respiratory health of residents living in and around the town of Humboldt, Saskatchewan, Canada. There were 2090 adults age 18-79 years who completed a questionnaire that included a medical and smoking history, as well as socio-economic and lifestyle variables. Genetic information and lung function test measurements were available on 1725 subjects (754 males and 971 females) of the 2090 respondents. These subjects were selected for further analysis to investigate the association between TLR4 Asp299Gly genotype and forced expiratory volume in the first second in liters (FEV₁), forced vital capacity in liters (FVC), FEV₁/FVC ratio, and forced expiratory flow rate in liters/second (FEF_25-75). Multivariable linear regression analysis was used to investigate associations.

Results

Adjusted mean values of FEV₁ and FVC were significantly different between TLR4 wild type and TLR4 variant groups [Mean ± S.E.: (TLR4 wild type - FEV₁: 3.18 ± 0.02, FVC: 3.95 ± 0.03; TLR4 variant - FEV₁: 3.31 ± 0.06, FVC: 4.14 ± 0.07)]. Based on multivariable regression analysis, we observed that body mass index (BMI) was associated with decreased FEV₁/FVC ratio and FEF_25-75 in TLR4 variant group but not in wild type group.

Conclusion

BMI may modify the associations of TLR4 Asp299Gly polymorphism with FEV₁/FVC ratio and FEF_25-75.

Asthma, smoking and BMI in adults with intellectual disabilities: a community-based survey

BACKGROUND

Recent research evidence from the general population has shown that tobacco smoking and raised body mass index (BMI) are associated with worse asthma outcomes. There are indications that asthma morbidity and mortality may be higher among people with intellectual disabilities (ID) than the general population, but the reason for this is not known. This is the first study to investigate the extent of smoking and higher than recommended BMI among adults with ID and a diagnosis of asthma.

METHOD

Health-related data for 1097 adults with ID were collected from 28 primary care practices in Bristol, UK.

RESULTS

Prevalence of asthma in this sample of adults with ID was 12% which was much higher than among the general population living in the region. The 132 patients with asthma were found to be nearly twice as likely to be current smokers as patients with ID who did not have asthma (29.5% vs. 15.6%). Smoking rates were higher among men than women with asthma (35.7% vs. 22.6%). Patients diagnosed with asthma were also more likely to be obese (BMI >or= 30) than patients with ID but no asthma (42.7% vs. 31.6%). Obesity was particularly a problem among women with asthma as more than half (52.1%) had a BMI >or= 30.

CONCLUSIONS

A very high proportion of patients with ID and asthma were found to be current smokers and/or obese. There is now strong research evidence that both smoking and obesity are implicated in the development of asthma and associated with worse disease outcomes. This study highlights the urgent need for programmes aimed at providing support for people with ID and asthma to stop smoking and to achieve a healthy body weight.

Synergy of BMI and family history on diabetes: the Humboldt Study

Objective

To examine the joint effect of family history and BMI on diabetes.

Design

Cross-sectional study.

Setting

A rural community in Saskatchewan, Canada.

Subjects

The analysis was based on data from 2081 adults, 18–79 years of age, who participated in the Humboldt Study conducted in 2003. Doctor-diagnosed diabetes and family history of diabetes of biological parents and siblings were self-reported. Body weight and height were objectively measured. The interaction of family history and BMI on diabetes was assessed on an additive scale.

Results

The prevalence of diabetes was 7·9 %, and BMI and history of diabetes were two important predictors. The adjusted prevalence ratios were 1·76 (95 % CI 1·37, 2·27) and 2·59 (95 % CI 2·05, 3·31) for those with a BMI of 25·0–29·9 kg/m2 and of at least 30 kg/m2, respectively, compared with a BMI of less than 25 kg/m2, and was 2·41 (95 % CI 2·08, 2·80) for those with a family history of diabetes v. those without. The data indicated an additive interaction of family history and BMI on diabetes.

Conclusions

When exposed to both family history and overweight/obesity, individuals would have an increased risk that was greater than the sum of their single effects. Reduction of BMI would also reduce the risk of diabetes associated family history.

Atopy, obesity, and asthma in adults: the Humboldt study

Obesity appears more strongly associated with asthma in women than in men. It is hypothesized that a stronger linkage of obesity with nonatopic asthma than with atopic asthma may explain the sex difference. That being the case, we might hypothesize a stronger association between obesity and asthma in nonatopic individuals than in atopic ones. In this analysis, we examined the association between obesity and asthma in atopic and nonatopic people separately. A total of 1997 residents aged 18 to 79 years who participated in the 2003-2004 Humboldt study were included in the analysis. Body mass index (BMI) and waist circumference were objectively measured. Allergy skin tests were conducted to determine atopic sensitization. Respiratory allergy and physician diagnosed asthma were self-reported. Overall, 8% reported having asthma, 30% had atopic sensitization as determined by allergy skin tests, 31% reported a history of respiratory allergy, and 35% were obese defined as BMI equal to or larger than 30 kg/m(2). Compared to those with a BMI <25 kg/m(2), the odds ratio for asthma for the nonatopic subjects of those with a BMI of at least 30.0 kg/m(2) was 2.01 (95% confidence interval [CI]: 1.13, 3.59] after adjustment for sex and age. The association between obesity and asthma was not statistically significant in atopic subjects. The adjusted odds ratios for obesity versus normal weight were 2.56 (95% CI: 1.07, 6.12) and 1.76 (95% CI: 1.04, 3.01) for those without and with a history of respiratory allergy, respectively. The association of asthma with waist circumference was not statistically significant in all the subgroups defined by atopy and respiratory allergy. The data suggested a stronger association between obesity and asthma among nonatopic people than among atopic people.

Contribution of functional variation in the IL13 gene to allergy, hay fever and asthma in the NSHD longitudinal 1946 birth cohort

BACKGROUND

Genetic variants of the two adjacent genes, IL13 and IL4 have frequently been reported as being associated with susceptibility to atopy and asthma, both in adults and children, and some studies also suggest association with lung function and chronic obstructive pulmonary disease.

METHODS

In this study, we examined for the first time the effect of these variants in 2918 adults in a longitudinal birth cohort, the British National Survey of Health and Development, where there are extensive life style, developmental and environmental data. We examine two IL13 single nucleotide polymorphisms (SNPs) IL13 rs20541 (R110Q) and rs1800925 (-1024C>T) and one IL4 SNP, rs2070874 (-33C>T) with likely function.

RESULTS

We show that IL13 rs20541 and rs1800925 are each significantly associated with self-reported asthma and allergy, and that this association is not confounded by any of the known developmental and environmental risk factors for asthma and atopy, including in particular place of birth. IL13 rs20541 does however act as a confounder for the IL13 rs1800925 associations, meaning that there is no statistical support for rs1800925 having an independent effect. There is nevertheless evidence for interaction between smoking and rs1800925, with allergy as outcome. None of the SNPs showed association with measures of lung function, nor any interaction with the effect of smoking on lung function.

CONCLUSION

In a longitudinal population cohort we have established a role for polymorphism of IL13 in determining susceptibility to both atopy and asthma.

The role of physical activity and body mass index in the health care use of adults with asthma

BACKGROUND

Health care use in patients with asthma is affected by many factors, including sex and ethnicity. The role of physical activity (PA) and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) in this relationship is unknown.

OBJECTIVE

To determine the role of PA and BMI in the health care use of patients with asthma.

METHODS

A sample of adults with asthma (n=6,835) and without asthma (n=78,051) from cycle 3.1 of the Canadian Community Health Survey was identified. Health care use was self-reported as overnight hospital stays (yes or no), length of overnight hospital stay (<4 or > or =4 nights), and physician consultations (<3 or > or =3). Self-reported physical activities were used to derive total energy expenditure and to classify participants as active (>3.0 kcal/kg of body weight per day), moderately active (1.5-3.0 kcal/kg of body weight per day), and inactive (<1.5 kcal/kg of body weight per day). The BMI was categorized as normal weight (18.5-24.9), overweight (25.0-29.9), and obese (30.0-59.9).

RESULTS

Adjusted logistic regression models revealed that patients with asthma were more likely to have an overnight hospital stay (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.95-2.60), 4 or more overnight hospital stays (OR, 1.48; 95% CI, 1.12-1.96), and 3 or more physician consultations (OR, 2.43; 95% CI, 2.18-2.71) compared with patients without asthma (OR, 1.00). Inactive patients with asthma were more likely to have an overnight hospital stay (OR, 1.68; 95% CI, 1.31-2.16) and 3 or more physician consultations (OR, 1.23; 95% CI, 1.04-1.46) than active patients with asthma (OR, 1.00). Inactive/obese patients with asthma were 2.35 (95% CI, 1.69-3.27) times more likely to have an overnight hospital stay and 2.76 (95% CI, 2.11-3.60) times more likely to have 3 or more physician consultations than active/normal weight patients with asthma (OR, 1.00).

CONCLUSIONS

Higher PA levels are associated with lower health care use in individuals with and without asthma. In those with asthma, PA was a more important factor in overnight hospital stays than BMI, whereas both BMI and PA were important determinants of physician consultations.

Gender differences in the association of overweight and asthma morbidity among urban adolescents with asthma

Asthma and obesity disproportionately affect US African-American youth. Among youth with asthma, obesity has been associated with poor control. The impact of gender on this association is unclear. We examined these relationships in a sample of urban, African-American adolescents with asthma. Questionnaires were used to identify high school students with asthma, and to examine the association of body mass index (BMI) to asthma morbidity, by gender. Of 5967 students completing questionnaires, 599 (10%) met criteria for asthma and 507 had data sufficient for inclusion in further analyses (46% male, mean age = 15.1 yr). Univariately, BMI > 85th percentile was significantly related only to reported emergency department visits (ED) and school days missed for any reason, Odds Ratio (95%Confidence Interval) = 1.7(1.1-2.7), p = 0.01 and 1.8(1.1-3.0), p = 0.01, respectively. A significant gender-BMI interaction (p < 0.05) was observed in multivariate models for ED visits, hospitalizations and school days missed for asthma. In gender-specific models, adjusted Risk Ratios for BMI > 85th and ED visits, hospitalizations, and school days missed because of asthma were 1.7(0.9-3.2), 6.6(3.1-14.6) and 3.6(1.8-7.2) in males. These associations were not observed in females. Gender modifies the association between BMI and asthma-related morbidity among adolescents with asthma. Results have implications for clinical management as well as future research.

Comparison of anthropometric measures of obesity in childhood allergic asthma: central obesity is most relevant

BACKGROUND

Established indicators of central obesity include waist circumference, waist/height ratio, and the conicity index. Studies using such measures (as opposed to body mass index [BMI] percentiles) to characterize the association between obesity and asthma are lacking, despite the fact that these measures have been shown to be most relevant for many other chronic diseases.

OBJECTIVES

We sought to examine measures assessing the distribution of obesity in the context of childhood allergic rhinitis and asthma and to elucidate the association of obesity, including central obesity, with allergic asthma in children.

METHODS

Children with allergic rhinitis with (cases) or without (control subjects) asthma were recruited. BMI percentiles were derived by using national growth charts. Waist circumference, waist/height ratio, and conicity index values were obtained.

RESULTS

Central obesity was associated with asthma, asthma severity, lower lung function, and reduced atopy in asthmatic subjects.

CONCLUSION

Measures of central obesity are more associated with the presence of asthma and asthma severity in children with allergic rhinitis when compared with standard BMI measures.