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

Sleeve Gastrectomy is Associated with Longitudinal Improvements in Lung Function and Patient-Reported Respiratory Outcomes

PURPOSE

Obesity exerts negative effects on pulmonary function through proven mechanical and biochemical pathways. Multiple studies have suggested that bariatric surgery can improve lung function. However, the timing of these effects on lung function and its association with patient reported outcomes is not known.

MATERIALS AND METHODS

A prospective cohort study of patients undergoing laparoscopic sleeve gastrectomy (LSG) at a tertiary care hospital was undertaken. Spirometry tests, laboratory tests, and self-reported questionnaires on asthma symptoms and asthma control (ACQ and ACT) were administered. All data were recorded pre-operatively (T0) and every 3 months post-operatively for 1 year (T3, T6, T9, T12) and were compared using a mixed-models approach for repeated measures.

RESULTS

For the 23 participants, mean age was 44.2 ± 12.3 years, mean BMI was 45.2 ± 7.2 kg/m2, 18(78%) were female, 9(39%) self-reported as non-white and 6(26%) reported to have asthma. Following LSG, % total body weight loss was significant at all follow-up points (P < 0.0001). Rapid improvement in forced expiratory volume (FEV)% predicted and forced vital capacity (FVC)% predicted was seen at T3. Although the overall ACQ and ACT score remained within normal range throughout the study, shortness of breath declined significantly at 3 months post-op (P < 0.05) and wheezing resolved for all patients by twelve months. Patients also reported reduced frequency of sleep interruption and inability to exercise by the end of the study (P < 0.05).

CONCLUSION

Improvements in objective lung function assessments and patient-reported respiratory outcomes begin as early as 3 months and continue until 12 months after sleeve gastrectomy.

The associations between asthma and common comorbidities: a comprehensive Mendelian randomization study

Background

Asthma is a chronic respiratory disease and is often associated with multiple comorbidities. The causal relationship between asthma and these comorbidities is still unclear. This study aimed to investigate the association between genetically predicted asthma and common comorbidities.

Methods

After searching PubMed and GWAS summary statistics, we identified 26 comorbidities of asthma. The causal relationship between asthma and comorbidities was assessed in two independent GWASs by bidirectional Mendelian randomization, followed by validation of the results using a multivariate Mendelian randomization analysis and several sensitivity analyses.

Results

In the bidirectional Mendelian randomization analysis, chronic sinusitis [odds ratio (OR) = 1.54, p = 1.40 × 10-5], atopic dermatitis (OR = 1.36, p = 9.37 × 10-21), allergic conjunctivitis (OR = 2.07, p = 4.32 × 10-6), and allergic rhinitis (OR = 1.53, p = 5.20 × 10-6) were significantly associated with increased asthma risk. Hyperthyroidism (OR = 1.12, p = 0.04) had a potential increased risk for asthma. For the reverse direction, asthma showed significant associations with an increased risk of chronic obstructive pulmonary disease (OR = 1.24, p = 2.25 × 10-9), chronic sinusitis (OR = 1.61, p = 5.25 × 10-21), atopic dermatitis (OR = 2.11, p = 1.24 × 10-24), allergic conjunctivitis (OR = 1.65, p = 6.66 × 10-35), allergic rhinitis (OR = 1.90, p = 2.38 × 10-57), and a potential higher risk of allergic urticaria (OR = 1.25, p = 0.003).

Conclusion

This study suggested a significant bidirectional association of chronic sinusitis, atopic dermatitis, allergic conjunctivitis, and allergic rhinitis with asthma. In addition, hyperthyroidism was associated with an increased risk of asthma and asthma increased the risk of chronic obstructive pulmonary disease and allergic urticaria.

Causal risk factors for asthma in Mendelian randomization studies: A systematic review and meta-analysis

BACKGROUND

Several risk factors for asthma have been proposed; however, the causality of these associations is sometimes unclear. Mendelian randomization is a powerful epidemiological approach that can help elucidate the causality of risk factors. The aim of the present study was to identify causal risk factors for asthma through Mendelian Randomization studies.

METHODS

A systematic search of PubMed and EMBASE was conducted, to identify studies investigating risk factors for asthma or respiratory allergies through Mendelian Randomization. When two or more studies investigated the same risk factor a meta-analysis was conducted. Of 239 studies initially identified, 41 were included.

RESULTS

A causal association between adiposity and adult asthma risk was found in 10 out of 12 studies with a summary risk ratio of 1.05 per kg/m² increase in BMI (95% CI: 1.03-1.07). Puberty timing (n = 3), alcohol (n = 2), and linoleic acid (n = 1) had causal effects on asthma risk, while vitamins/minerals (n = 6) showed no consistent effect on asthma. The effect of smoking on adult asthma conflicted between studies. Several of the significant associations of asthma with immune related proteins (n = 5) and depression (n = 2) investigated through multiple traits analyses could generally benefit from replications in independent datasets.

CONCLUSION

This systematic review and meta-analysis found evidence for causal effects of adiposity, puberty timing, linoleic acid, alcohol, immune related proteins, and depression on risk of asthma.

Plasma adiponectin and risk of asthma: observational analysis, genetic Mendelian randomisation and meta-analysis

BACKGROUND

Adiponectin, an adipocyte-secreted protein-hormone with inflammatory properties, has a potentially important role in the development and progression of asthma. Unravelling whether adiponectin is a causal risk factor for asthma is an important issue to clarify as adiponectin could be a potential novel drug target for the treatment of asthma.

OBJECTIVE

We tested the hypothesis that plasma adiponectin is associated observationally and causally (using genetic variants as instrumental variables) with risk of asthma.

METHODS

In the Copenhagen General Population Study, we did an observational analysis in 28 845 individuals (2278 asthma cases) with plasma adiponectin measurements, and a genetic one-sample Mendelian randomisation analysis in 94 868 individuals (7128 asthma cases) with 4 genetic variants. Furthermore, in the UK Biobank, we did a genetic two-sample Mendelian randomisation analysis in 462 933 individuals (53 598 asthma cases) with 12 genetic variants. Lastly, we meta-analysed the genetic findings.

RESULTS

While a 1 unit log-transformed higher plasma adiponectin in the Copenhagen General Population Study was associated with an observational OR of 1.65 (95% CI 1.29 to 2.08) for asthma, the corresponding genetic causal OR was 1.03 (95% CI 0.75 to 1.42). The genetic causal OR for asthma in the UK Biobank was 1.00 (95% CI 0.99 to 1.00). Lastly, genetic meta-analysis confirmed lack of association between genetically high plasma adiponectin and causal OR for asthma.

CONCLUSION

Observationally, high plasma adiponectin is associated with increased risk of asthma; however, genetic evidence could not support a causal association between plasma adiponectin and asthma.

Cross-Sectional Association Between Exclusive and Concurrent Use of Cigarettes, ENDS, and Cigars, the Three Most Popular Tobacco Products, and Wheezing Symptoms Among U.S. Adults

INTRODUCTION

This study assessed the association of exclusive and concurrent use of cigarettes, electronic nicotine delivery systems (ENDS), and cigars with ever and past 12-month wheezing symptoms among a nationally representative sample of US adult current tobacco users.

METHODS

Cross-sectional data from the Population Assessment of Tobacco and Health (PATH) Study Wave 3 (W3) were used. The weighted prevalence of self-reported ever and past 12-month wheezing symptoms for noncurrent users compared with users of cigarettes, ENDS, cigars, and any combination of these products (polytobacco use of these tobacco products) were presented for 28 082 adults. The cross-sectional association of tobacco use with self-reported wheezing symptoms was assessed using weighted multivariable and ordinal logistic regression with consideration of complex sampling design.

RESULTS

Significantly higher odds of ever had wheezing or whistling in the chest at any time in the past were observed among current cigarette (adjusted odds ratio: 2.62, 95% confidence intervals [CI]: 2.35, 2.91), ENDS (1.49, 95% CI: 1.14, 1.95), and polytobacco users (2.67, 95% CI: 2.26, 3.16) compared with noncurrent users. No associations were seen for cigar use. Polytobacco use was associated with a higher odds of ever wheezing when compared with exclusive ENDS (1.61, 95% CI: 1.19, 2.17) and exclusive cigar use (2.87, 95% CI: 1.93, 4.26), but not exclusive use of cigarettes.

CONCLUSIONS

Ever wheezing is associated with the use of cigarettes, ENDS, and polytobacco use of cigarettes, ENDS, and/or cigars, but not cigar use. The association of polytobacco use and wheezing appears to be driven by cigarette use.

IMPLICATIONS

Cross-sectional associations with ever and past 12-month wheezing symptoms were found to be the strongest among cigarette users, exclusively or in combination. Future longitudinal research is needed to better understand how cigarette use interacts with other tobacco and nicotine products and contributes to respiratory symptoms.

A life course approach to elucidate the role of adiposity in asthma risk: evidence from a Mendelian randomisation study

BACKGROUND

Adiposity is associated with asthma although studies do not usually explore the inter-related role of childhood and adult adiposity in asthma risk using a life course perspective.

METHODS

We conducted a Mendelian randomisation (MR) study using genetic instruments for childhood body mass index (BMI) (n=47 541), childhood obesity (n=29 822) and adult BMI (n=681 725) applied to the UK Biobank (n=401 837), with validation in a genome-wide association study of asthma (GABRIEL, n=5616). We used inverse variance weighting and other sensitivity analyses to examine the relationship between adiposity and asthma risk. We assessed mediation using multivariable Mendelian randomisation (MVMR) analysis.

RESULTS

Childhood BMI was related to asthma in the UK Biobank (OR 1.10 per SD increase, 95% CI 0.99 to 1.22). Adult BMI was associated with asthma risk (OR 1.33 per SD increase, 95% CI 1.25 to 1.43). Analyses in GABRIEL gave directionally consistent results but with wide CI. The relationship between childhood obesity and asthma risk was less clear in both data sources. MVMR suggested the relation of childhood BMI with asthma risk was largely mediated via adult BMI.

CONCLUSION

Adiposity in childhood likely cause asthma, but the effect is primarily mediated via adult BMI.

The Dynamic Relationship Between Asthma and Obesity in Schoolchildren

Asthma and obesity are among the most prevalent chronic health conditions in children. Although there has been compelling evidence of co-occurrence of asthma and obesity, it is uncertain whether asthma contributes to the development of obesity or obesity contributes to the onset of asthma or both. In this study, we used a joint transition modeling approach with cross-lagged structure to understand how asthma and obesity influence each other dynamically over time. Subjects for this study included 5,193 kindergarten and first-grade students enrolled from 13 communities in 2002-2003 in the Southern California Children's Health Study, with up to 10 years of follow-up. We found that nonobese children with diagnosed asthma at a study visit were at 37% higher odds of becoming obese by the next annual visit compared with children without asthma (odds ratio = 1.38; 95% credible interval: 1.12, 1.71). However, the presence of obesity at the current visit was not statistically significantly associated with asthma onset in the next visit (odds ratio = 1.25; 95% credible interval: 0.94, 1.62). In conclusion, childhood asthma appears to drive an increase in the onset of obesity among schoolchildren, while the onset of obesity does not necessarily imply the future onset of asthma, at least in the short term.

Adiposity and asthma in adults: a bidirectional Mendelian randomisation analysis of The HUNT Study

BACKGROUND

We aimed to investigate the potential causal associations of adiposity with asthma overall, asthma by atopic status or by levels of symptom control in a large adult population and stratified by sex. We also investigated the potential for reverse causation between asthma and risk of adiposity.

METHODS

We performed a bidirectional one-sample Mendelian randomisation (MR) study using the Norwegian Nord-Trøndelag Health Study population including 56 105 adults. 73 and 47 genetic variants were included as instrumental variables for body mass index (BMI) and waist-to-hip ratio (WHR), respectively. Asthma was defined as ever asthma, doctor-diagnosed asthma and doctor-diagnosed active asthma, and was further classified by atopic status or levels of symptom control. Causal OR was calculated with the Wald method.

RESULTS

The ORs per 1 SD (4.1 kg/m²) increase in genetically determined BMI were ranged from 1.36 to 1.49 for the three asthma definitions and similar for women and men. The corresponding ORs for non-atopic asthma (range 1.42-1.72) appeared stronger than those for the atopic asthma (range 1.18-1.26), but they were similar for controlled versus partly controlled doctor-diagnosed active asthma (1.43 vs 1.44). There was no clear association between genetically predicted WHR and asthma risk or between genetically predicted asthma and the adiposity markers.

CONCLUSIONS

Our MR study provided evidence of a causal association of BMI with asthma in adults, particularly with non-atopic asthma. There was no clear evidence of a causal link between WHR and asthma or of reverse causation.

Genuair®/Pressair® Inhaler in COPD: The Patient Perspective

This article reviews the latest data pertaining to the Genuair^®/Pressair^® device, a breath-actuated, multi-dose dry-powder inhaler with a two-step inhalation process, which is marketed for the delivery of aclidinium alone or in combination with formoterol for long-term maintenance bronchodilation treatment in chronic obstructive pulmonary disease. It contains multiple feedback mechanisms to guide effective use, and safety features to avoid double-dosing or attempted use when empty. In addition to describing the design of Genuair^®, the article will provide an update on inhaler operability and performance, focusing on recent patient preference and satisfaction studies. The evidence suggests that patients find Genuair^® easy to use, with patients requiring less training and making fewer inhalation errors than with other inhalers, and that patient satisfaction with the device is high.

Elucidation of causal direction between asthma and obesity: a bi-directional Mendelian randomization study

BACKGROUND

Observational associations between asthma and obesity are well established, but inferring causality is challenging. We leveraged publicly available summary statistics to ascertain the causal direction between asthma and obesity via Mendelian randomization in European-ancestry adults.

METHODS

We performed two-sample bi-directional Mendelian randomization analysis using publicly available genome-wide association studies summary statistics. Single nucleotide polymorphisms associated with asthma and body mass index at genome-wide significance were combined using a fixed effect meta-analysis in each direction. An extensive sensitivity analysis was considered.

RESULTS

There was evidence in support of increasing causal effect of body mass index on risk of asthma (odds ratio 1.18 per unit increase, 95% confidence interval (CI) (1.11, 1.25), P = 2 × 10-8. No significant causal effect of asthma on adult body mass index was observed [estimate -0.004, 95% CI (-0.018, 0.009), P = 0.553].

CONCLUSIONS

Our results confirmed that in European-ancestry populations, adult body mass index is likely to be causally linked to the risk of asthma; yet the effect of asthma on body mass index is small, if present at all.

Associations between vitamin D, adiposity, and respiratory symptoms in chronic spinal cord injury

Context/Objective Persons with chronic spinal cord injury (SCI) have an increased risk of respiratory-related morbidity and mortality and chronic respiratory symptoms are clinical markers of future respiratory disease. Therefore, we sought to assess potentially modifiable factors associated with respiratory symptoms, with a focus on circulating vitamin D and measures of body fat. Design Cross-sectional study. Setting Veterans Affairs Medical Center. Participants Three hundred forty-three participants (282 men and 61 women) with chronic SCI participating in an epidemiologic study to assess factors influencing respiratory health recruited from VA Boston and the community. Methods Participants provided a blood sample, completed a respiratory health questionnaire, and underwent dual x-ray absorptiometry (DXA) to assess % body fat. Logistic regression was used to assess cross-sectional associations between respiratory symptoms and plasma vitamin D and measures of body fat with adjustment for a number of potential confounders. Outcome Measures Chronic cough, chronic phlegm, any wheeze, persistent wheeze. Results After adjustment for a number of confounders (including smoking), participants with greater %-android, gynoid, trunk, or total body fat had increased odds ratios for any wheeze and suggestive associations with persistent wheeze, but not with chronic cough or phlegm. Vitamin D levels were not associated with any of the respiratory symptoms. Conclusion Increased body fat, but not vitamin D, was associated with wheeze in chronic SCI independent of a number of covariates.

Genetics of obesity: what genetic association studies have taught us about the biology of obesity and its complications

Genome-wide association studies (GWAS) for BMI, waist-to-hip ratio, and other adiposity traits have identified more than 300 single-nucleotide polymorphisms (SNPs). Although there is reason to hope that these discoveries will eventually lead to new preventive and therapeutic agents for obesity, this will take time because such developments require detailed mechanistic understanding of how an SNP influences phenotype (and this information is largely unavailable). Fortunately, absence of functional information has not prevented GWAS findings from providing insights into the biology of obesity. Genes near loci regulating total body mass are enriched for expression in the CNS, whereas genes for fat distribution are enriched in adipose tissue itself. Gene by environment and lifestyle interaction analyses have revealed that our increasingly obesogenic environment might be amplifying genetic risk for obesity, yet those at highest risk could mitigate this risk by increasing physical activity and possibly by avoiding specific dietary components. GWAS findings have also been used in mendelian randomisation analyses probing the causal association between obesity and its many putative complications. In supporting a causal association of obesity with diabetes, coronary heart disease, specific cancers, and other conditions, these analyses have clinical relevance in identifying which outcomes could be preventable through weight loss interventions.

Relationships between self-reported asthma and pulmonary function and various measures of obesity

OBJECTIVE

We explore the association with self-reported asthma and pulmonary function based on spirometry measurements using different measures to determine obesity because body mass index (BMI) is limited in not differentiating fat and muscle mass.

METHODS

A multi-year cross-sectional study using Korean National Health and Nutrition Examination Survey data was conducted between July 2008 and May 2011. A total of 9409 subjects were included in the final analysis.

RESULTS

Obesity was associated with self-reported asthma and pulmonary function limitations mainly in adult women aged between 40 and 65 years and elderly men aged 65 or older. The association was stronger when the measurement of obesity was based on body fat percentage or waist-to-height ratio (WHtR), compared to BMI. There was a higher self-reported asthma risk among obese women according to the WHtR [odds ratio (OR) = 1.817, 95% CI: (1.208, 2.735)]. There was an increased risk of pulmonary function limitation with abdominal obesity [OR 1.418, 95% CI (1.020, 1.972)], weight-to-height ratio [OR 1.467, 95% CI (1.058, 2.034)], and obesity with regard to body fat percentage [OR 1.753, 95% CI (1.251, 2.457)] in adult women. In elderly men, obesity based on body fat percentage was associated with an increased risk of pulmonary function limitation [OR 1.93, 95% CI (1.098, 3.388)].

CONCLUSIONS

Measures other than BMI should be examined when investigating the effect of obesity on self-reported asthma and pulmonary function limitation.

Risk Factors for Chronic Cough Among 14,669 Individuals From the General Population

BACKGROUND

Risk factors for chronic cough in the general population have not been described systematically. We identified and ranked chronic cough risk factors at the individual and community level using data from 14,669 individuals from the Copenhagen General Population Study.

METHODS

Severity of chronic cough was assessed using the Leicester Cough Questionnaire (LCQ). We ranked chronic cough risk factors based on magnitude of age-adjusted ORs at the individual level and of the population attributable risks (PARs) at the community level.

RESULTS

Prevalence of chronic cough in the general population was 4% overall and 3% in never smokers, 4% in former smokers, and 8% in current smokers. Median score of the LCQ was 5.8 (25th-75th percentile, 5.0-6.3) for physical domain, 5.6 (25th-75th percentile, 4.6-6.3) for psychologic domain, 6.3 (25th-75th percentile, 5.5-6.8) for social domain, and 17.3 (25th- 75th percentile, 15.4-18.9) in total. At the level of the individual, age-adjusted ORs for the three top-ranked risk factors were 5.0 (95% CI, 1.4-18) for bronchiectasis, 2.6 (95% CI, 1.7-3.9) for asthma and 2.3 (95% CI, 1.5-3.4) for gastroesophageal reflux disease in never smokers, 7.1 (95% CI, 2.6-20) for bronchiectasis, 3.1 (95% CI, 2.2-4.4) for asthma and 2.2 (95% CI, 1.5-3.2) for occupational exposure to dust/fumes in former smokers, and 1.9 (95% CI, 1.3-2.9) for airflow limitation in current smokers. At the level of the community, the three top-ranked risk factors were female sex (PAR, 19%), asthma (PAR, 10%), and gastroesophageal reflux disease (PAR, 8%) in never smokers; abdominal obesity (PAR, 20%), low income (PAR, 20%), and asthma (PAR, 13%) in former smokers; and airflow limitation (PAR, 23%) in current smokers.

CONCLUSIONS

Risk factors for chronic cough differ at the level of the individual and community, and by smoking status. Strategies to prevent and treat modifiable chronic cough risk factors should be tailored accordingly.

Relationship of Allergy with Asthma: There Are More Than the Allergy "Eggs" in the Asthma "Basket"

Asthma and allergy share a similar and very close course, especially through childhood. Considerable research effort has been put in untangling these associations; however, it is now becoming obvious that this is an exceedingly difficult task. In fact, each research breakthrough further perplexes this picture, as we are steadily moving toward the era of personalized medicine and we begin to appreciate that what we thought to be a single disease, asthma, is in fact an accumulation of distinct entities. In the context of this "syndrome," which is characterized by several, as of yet poorly defined endotypes and phenotypes, the question of the link of "asthma" with allergy probably becomes non-relevant. In this review, we will revisit this question while putting the emphasis on the multifaceted nature of asthma.

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.