Association of novel adult cough subclasses with clinical characteristics and lung function across six decades of life in a prospective, community-based cohort in Australia: an analysis of the Tasmanian Longitudinal Health Study (TAHS)

Systemic inflammation mediates the relationship between urinary cadmium and chronic cough risk: findings based on multiple statistical models

Epidemiological research examining the relationship between urinary cadmium and the risk of chronic cough remains scarce. This study included 2965 participants for a cross-sectional study from the NHANES. The weighted quantile sum (WQS) regression, bayesian kernel machine regression (BKMR), machine learning models (support vector machines, random forests, decision trees, and XGBoost), restricted cubic spline (RCS), and logistic regression were applied to comprehensively evaluate the performance of urinary metals in predicting chronic cough risk. Finally, the mediation effect model was employed to evaluate the role of systematic inflammation in the relationship between urinary cadmium and the risk of chronic cough. Urinary cadmium correlated with an increasing risk of chronic cough in the multivariate logistic regression model (OR: 2.83, 95% CI: 1.60-4.99). Both the WQS regression and BKMR consistently suggested a positive relationship between urinary mixed metal and chronic cough risk. Among the four machine learning models used to evaluate urinary metals and the risk of chronic cough, the random forests model showed better predictive performance (AUC = 0.69). The random forests suggested that the top five important indicators for predicting chronic cough risk were urinary cadmium, thallium, molybdenum, cesium, and uranium. Finally, the mediation effect model suggested that the systematic inflammation (lymphocytes: 4.24%, systemic immune inflammation index: 5.11%) partially mediated the relationship between urinary cadmium and chronic cough risk. This study discovered that urinary cadmium was elevated in correlation with the increasing risk of chronic cough. Systematic inflammations may partially mediate this association. Improving exposure to urinary cadmium may reduce the risk of chronic cough.

The Clinical Approach to Chronic Cough

Chronic cough remains a significant clinical challenge, affecting approximately 10% of the population and leading to significant impairment in psychological, social, and physical quality of life. In recent years, efforts have intensified to elucidate the mechanisms underlying chronic cough and to focus on investigating and treating refractory chronic cough (RCC). A "treatable trait" approach, which focuses on identifying and addressing the specific associated causes of chronic cough, has gained traction. In some patients, RCC is likely driven by a neuropathic mechanism due to dysregulation of the neuronal pathways involved in the cough reflex, often clinically described as cough hypersensitivity syndrome. Although the initial treatment of underlying conditions remains central to managing treatable traits, the therapeutic options for RCC have expanded to include targeting cough hypersensitivity. First-line treatments now include neuromodulators and speech therapy with one P2X3 receptor antagonist (gefapixant) recently licensed in the European Union, United Kingdom, and Japan. Despite these advances, patient responses remain variable, underscoring the ongoing need for research into the pathophysiology and treatment of RCC. This article reviews current investigations and management options in treating chronic cough and RCC.

Associations between life-course FEV1/FVC trajectories and respiratory symptoms up to middle age: analysis of data from two prospective cohort studies

BACKGROUND

Life-course lung function trajectories leading to airflow obstruction, as measured by impaired FEV1/FVC (forced vital capacity), precede the onset of chronic obstructive pulmonary disease (COPD). We aimed to investigate whether individuals on impaired FEV1/FVC trajectories have an increased burden of respiratory symptoms, including those who do not meet the spirometric criteria for COPD.

METHODS

We analysed serial life-course data from two population-based cohort studies separately, which included respiratory symptoms and spirometry: the Tasmanian Longitudinal Health Study (TAHS, Australia) cohort was recruited at age 6-7 years and followed up until middle age (mean age 53 years; range 51-55); and the Coronary Artery Risk Development in Young Adults (CARDIA, USA) cohort was recruited at a mean age of 25 years (range 18-30) and followed up to a mean age of 55 years (range 47-64). Participants' symptom profiles at ages 53 and 55 years were derived by latent class analysis. Symptom profiles were compared across pre-bronchodilator FEV1/FVC trajectories derived by group-based modelling, then restricted to those without COPD defined by post-bronchodilator airflow obstruction (FEV1/FVC <5th percentile) at ages 51-55 years and 47-64 years.

FINDINGS

Six FEV1/FVC trajectories previously derived for TAHS were replicated in CARDIA. Optimal models identified five symptom profiles in TAHS (n=2421) and six in CARDIA (n=3153). For both cohorts, the most impaired FEV1/FVC trajectory (early low, rapid decline in TAHS; low peak, rapid decline in CARDIA) was associated with predominant wheeze (multinomial odds ratio [mOR] 6·71 [95% CI 4·10-10·90] in TAHS and 9·90 [4·52-21·70] in CARDIA) and nearly all respiratory symptoms (4·95 [2·52-9·74] and 14·80 [5·97-36·60]) at age 51-55 years in TAHS and age 47-64 years in CARDIA, compared with the average trajectory. Among individuals belonging to the three most impaired trajectories, the associations with predominant wheeze increased with worsening FEV1/FVC impairment and persisted when considering only those without spirometry-defined COPD. Additionally, for those belonging to the two rapid decline trajectories, both wheezing and usual phlegm or bronchitis were reported by 54 (20%) of 265 participants younger than 14 years in TAHS and by 31 (25%) of 123 participants aged 30 years or younger in CARDIA.

INTERPRETATION

In two independent cohorts that collected similar data, people on impaired FEV1/FVC trajectories often had a longstanding history of both wheeze and phlegm or bronchitis, and wheeze was the predominant symptom in individuals aged 47-64 years among those who had not already progressed to COPD.

FUNDING

National Health and Medical Research Council (Australia); The University of Melbourne; Clifford Craig Medical Research Trust; Victorian, Queensland & Tasmanian Asthma Foundations; Royal Hobart Hospital Research Foundation; Helen MacPherson Smith Trust; GlaxoSmithKline; National Heart, Lung, and Blood Institute of the US National Institutes of Health.

PM10 exposure induces bronchial hyperresponsiveness by upreguating acetylcholine muscarinic 3 receptor

Exposure to particulate matter (PM10) can induce respiratory diseases that are closely related to bronchial hyperresponsiveness. However, the involved mechanism remains to be fully elucidated. This study aimed to demonstrate the effects of PM10 on the acetylcholine muscarinic 3 receptor (CHRM3) expression and the role of the ERK1/2 pathway in rat bronchial smooth muscle. A whole-body PM10 exposure system was used to stimulate bronchial hyperresponsiveness in rats for 2 and 4 months, accompanied by MEK1/2 inhibitor U0126 injection. The whole-body plethysmography system and myography were used to detect the pulmonary and bronchoconstrictor function, respectively. The mRNA and protein levels were determined by Western blotting, qPCR, and immunofluorescence. Enzyme-linked immunosorbent assay was used to detect the inflammatory cytokines. Compared with the filtered air group, 4 months of PM10 exposure significantly increased CHRM3-mediated pulmonary function and bronchial constriction, elevated CHRM3 mRNA and protein expression levels on bronchial smooth muscle, then induced bronchial hyperreactivity. Additionally, 4 months of PM10 exposure caused an increase in ERK1/2 phosphorylation and increased the secretion of inflammatory factors in bronchoalveolar lavage fluid. Treatment with the MEK1/2 inhibitor, U0126 inhibited the PM10 exposure-induced phosphorylation of the ERK1/2 pathway, thereby reducing the PM10 exposure-induced upregulation of CHRM3 in bronchial smooth muscle and CHRM3-mediated bronchoconstriction. U0126 could rescue PM10 exposure-induced pathological changes in the bronchus. In conclusion, PM10 exposure can induce bronchial hyperresponsiveness in rats by upregulating CHRM3, and the ERK1/2 pathway may be involved in this process. These findings could reveal a potential therapeutic target for air pollution induced respiratory diseases.

Heritability of cough across two generations: the RHINESSA study

Aim

Heritability of cough has not yet been studied. We aimed to evaluate if individuals with cough are more likely to have offspring who develop cough, and if these associations differ by type of cough (productive/nonproductive).

Methods

The RHINESSA Generation Study (Respiratory Health In Northern Europe, Spain and Australia) includes 7155 parents (initially aged 30-54) answering detailed questionnaires in 2000 and 2010, and 8176 offspring ≥20 years answering similar questionnaires in 2012-2019. Chronic cough was categorised as productive or nonproductive (dry) cough. Associations between parental and offspring cough were analysed using mixed-effects logistic regression, adjusting for offspring age, sex, body mass index, smoking history, education level, current asthma, rhinitis, nocturnal gastroesophageal reflux; parent sex and smoking history; centre and family.

Results

Among parents with nonproductive cough, 11% of their offspring reported nonproductive cough, compared with 7% of offspring to parents without nonproductive cough, adjusted odds ratio (aOR) 1.59 (95% confidence interval 1.20-2.10). Among parents with productive cough, 14% of their offspring reported productive cough, compared with 11% of offspring to parents without productive cough, aOR 1.34 (1.07-1.67). No associations were found between parent productive cough-offspring nonproductive cough, nor between parent nonproductive cough-offspring productive cough.

Conclusions

Parents with chronic cough are more likely to have offspring with chronic cough independent of parental asthma, suggesting cough to be a separate heritable trait. The type of cough is important, as the nonproductive cough in parent associates only with nonproductive cough in offspring, and the same applied for productive cough.

Chronic Bronchitis in Children and Adults: Definitions, Pathophysiology, Prevalence, Risk Factors, and Consequences

The complex nature of chronic bronchitis (CB) and changing definitions have contributed to challenges in understanding its aetiology and burden. In children, CB is characterised by persistent airway inflammation often linked to bacterial infections and is therefore termed "protracted bacterial bronchitis" (PBB). Longitudinal studies suggest that CB in childhood persists into adulthood in a subgroup. It can also be associated with future chronic respiratory diseases including asthma, bronchiectasis, and chronic obstructive pulmonary disease (COPD). Adult CB is traditionally associated with smoking, occupational exposures, and lower socioeconomic status. The interplay between risk factors, childhood CB, adult CB, and other chronic respiratory diseases is intricate, requiring comprehensive longitudinal studies for a clearer understanding of the natural history of CB across the lifespan. Such longitudinal studies have been scarce to date given the logistic challenges of maintaining them over time. In this review, we summarise current evidence on the evolution of the definitions, pathophysiology, risk factors, and consequences of childhood and adulthood chronic bronchitis.

Endotypes of Paediatric Cough-Do They Exist and Finding New Techniques to Improve Clinical Outcomes

Chronic cough is a common symptom of many childhood lung conditions. Given the phenotypic heterogeneity of chronic cough, better characterization through endotyping is required to provide diagnostic certainty, precision therapies and to identify pathobiological mechanisms. This review summarizes recent endotype discoveries in airway diseases, particularly in relation to children, and describes the multi-omic approaches that are required to define endotypes. Potential biospecimens that may contribute to endotype and biomarker discoveries are also discussed. Identifying endotypes of chronic cough can likely provide personalized medicine and contribute to improved clinical outcomes for children.