Long-Term Prognosis of Asthma-Bronchiectasis Overlapped Patients: A Nationwide Population-Based Cohort Study

No causal association between serum vitamin D levels and bronchiectasis: A Mendelian randomization analysis

Observational studies have reported an association between Vitamin D deficiency and an increased risk of bronchiectasis. This study aims to investigate the causal relationship between Vitamin D levels and bronchiectasis using a 2-sample Mendelian randomization (MR) analysis. Data from 2 genome-wide association studies (GWAS) based on European ancestry were analyzed: serum vitamin D levels (sample size = 441,291 [UK Biobank]) and bronchiectasis (sample size = 187,830 [cases = 1107, controls = 186,723; FinnGen]). Inverse-variance weighted (IVW) analysis was primarily used to assess the causal effect of 25(OH)D levels on bronchiectasis, supplemented by Mendelian randomization Egger regression (MR-Egger), weighted median, simple mode, and weighted mode analyses. Additionally, MR-Egger intercept test and MR-Pleiotropy Residual Sum and Outlier methods were implemented to determine pleiotropy, and Cochran's Q test was conducted for heterogeneity testing. Leave-one-out analysis and Bayesian weighted Mendelian randomization was also used to assess the robustness of the results. The MR analysis suggested no significant causal effects of serum 25(OH)D levels on bronchiectasis using the IVW method (odds ratio = 1.550; 95% confidence interval [CI]: 0.908-2.315; P = .120). These results were consistent across MR-Egger regression, weighted median, simple mode, and weighted mode analyses. No significant heterogeneity, pleiotropy, or bias was detected in instrumental variables. Additionally, no evidence supported the causal effects of bronchiectasis on serum vitamin D levels (β = -0.002, 95% CI: -0.007 to 0.003; P = .463). Our study found no significant causal association between serum 25(OH)D levels and bronchiectasis, in either direction. A larger sample-sized randomized controlled trial (RCT) is needed to further investigate this potential causal relationship.

The Impact of Bronchiectasis on the Clinical Characteristics of Non-Severe Asthma

Current literature primarily delves into the relationship between bronchiectasis and severe asthma, and only a few studies have evaluated the impact of bronchiectasis in patients with non-severe asthma. Therefore, this study investigated the clinical impact of bronchiectasis in patients with non-severe asthma. A prospective observational study of 140 non-severe asthmatic patients with (bronchiectasis group) and without bronchiectasis (control group) was conducted between September 2012 and February 2022. The bronchiectasis and control groups were compared in terms of demographics, lung function, asthma control test (ACT) results, exacerbation history, and respiratory medications. Among 140 non-severe asthmatic subjects, approximately 15.7% (n = 22) had bronchiectasis. The most common type of bronchiectasis was cylindrical type (90.7%). The left lingular division was the most frequently involved lung lobe (20.4%). There were no significant differences in the demographics (age, sex, body mass index, smoking history, and comorbidities) or ACT results between the 2 groups. The bronchiectasis group used inhaled corticosteroids/long-acting β2-agonists (P = 0.074) and mucolytics (P < 0.001) more frequently than the control group. Compared to the control group, the bronchiectasis group had lower forced expiratory volume in 1 second (FEV1) (L) (1.9 ± 0.7 L vs. 2.3 ± 0.9 L, P = 0.039) and FEV1%predicted (67.2 ± 22.2%predicted vs. 77.1 ± 20.0%predicted, P = 0.038). The rate of hospital admission to a general ward in the preceding year was significantly higher in the bronchiectasis group compared to those of the control group (23.8% vs. 3.5%, P = 0.005) with an adjusted odds ratio of 6.308 (95% confidence interval, 1.401-28.392). Patients with non-severe asthma and bronchiectasis had lower lung function and more frequent exacerbations requiring hospitalization than those without bronchiectasis. More attention is needed for asthmatic patients with bronchiectasis, even if the asthma is not severe.

Impacts of Asthma in Patients With Bronchiectasis: Findings From the KMBARC Registry

PURPOSE

Although the coexistence of asthma and bronchiectasis is common, the impacts of asthma on bronchiectastic patients (BE) have not been well evaluated because this issue using bronchiectasis cohorts has been investigated in only a few studies.

METHODS

In the present study, 598 patients who were prospectively enrolled in the Korean bronchiectasis registry were evaluated. The clinical characteristics between BE with asthma and those without asthma were compared.

RESULTS

Asthma was found in 22.4% of BE. BE with asthma had a higher body mass index (BMI) (P = 0.020), more dyspnea (P < 0.001), larger sputum volume (P = 0.015), and lower forced expiratory volume in 1 second (FEV1) (P < 0.001) than those without asthma. BE with asthma had a higher rate of previous pneumonia (P = 0.017) or measles (P = 0.037) than those without asthma. Regarding treatment, BE with asthma used inhaled corticosteroids, long-acting muscarinic antagonists, and leukotriene receptor antagonists more frequently than those without asthma. Although intergroup differences were not observed in disease severity of bronchiectasis (P = 0.230 for Bronchiectasis Severity Index and P = 0.089 for FACED), the Bronchiectasis Health Questionnaire (BHQ) scores indicating the quality of life, were significantly lower in BE with asthma than in those without asthma (61.6 vs. 64.8, P < 0.001). In a multivariable model adjusting for age, sex, body mass index, forced expiratory volume in 1 second %predicted, sputum volume, modified Medical Research Council dyspnea scale ≥ 2, and the number of involved lobes, asthma was associated with lower BHQ scores (β-coefficient = -2.579, P = 0.014).

CONCLUSIONS

BE with asthma have more respiratory symptoms, worse lung function, and poorer quality of life than those without asthma. A better understanding of the impacts of asthma in BE will guide appropriate management in this population.

Asthma Phenotype with Metabolic Dysfunction

Asthma is chronic eosinophilic bronchitis with the dominancy of T helper 2 (Th2) inflammation. However, patients with asthma and metabolic dysfunction have pathogenic and pathological differences from those with Th2 inflammation. Metabolic dysfunction, typically presented as metabolic syndrome, has several important clinical components including central obesity, insulin resistance or glucose intolerance, dyslipidemia, and vitamin D deficiency. Data from large epidemiological studies support the significance of these components in the control of asthma and their contribution to airway remodeling, suggesting the presence of an asthma phenotype with metabolic dysfunction. These components are quite interactive with each other, so it is difficult to reveal the individual role of each. It is well known that asthma is difficult to treat in patients with obesity, due in part to inadequate response to inhaled corticosteroids. Additionally, vitamin D deficiency and insulin resistance have been regarded as aggravating factors of asthma control and airway remodeling. Recent clinical and in vivo studies have revealed the specific mechanisms of these components, which may aggravate asthma control and airway remodeling. In this review article, I summarize the recent studies and unmet needs for patients with asthma and metabolic dysfunction.