Health literacy and asthma: An update.

The US Department of Health and Human Services has defined health literacy (HL) as the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions. Structural and social determinants of health lead to low HL in approximately 36% of adults in the United States, where this condition is most prevalent in racial and ethnic minorities, economically disadvantaged communities, and immigrants with limited English proficiency. In turn, low HL can worsen asthma outcomes through direct effects (eg, nonadherence to or incorrect use of medications) and indirect effects (eg, an unhealthy diet leading to obesity, a risk factor for asthma morbidity). The purpose of this update is to examine evidence from studies on low HL and health and asthma outcomes published in the last 12 years, identify approaches to improve HL and reduce health disparities in asthma, and discuss future directions for research in this area under the conceptual framework of a socioecological model that illustrates the multifactorial and interconnected complexity of this public health issue at different levels.

Nasal epithelial gene expression and total IgE in children and adolescents with asthma.

BACKGROUND: Little is known about nasal epithelial gene expression and total IgE in youth. OBJECTIVE: We aimed to identify genes whose nasal epithelial expression differs by total IgE in youth, and group them into modules that could be mapped to airway epithelial cell types. METHODS: We conducted a transcriptome-wide association study of total IgE in 469 Puerto Ricans aged 9 to 20 years who participated in the Epigenetic Variation and Childhood Asthma in Puerto Ricans study, separately in all subjects and in those with asthma. We then attempted to replicate top findings for each analysis using data from 3 cohorts. Genes with a Benjamini-Hochberg-adjusted P value of less than .05 in the Epigenetic Variation and Childhood Asthma in Puerto Ricans study and a P value of less than .05 in the same direction of association in 1 or more replication cohort were considered differentially expressed genes (DEGs). DEGs for total IgE in subjects with asthma were further dissected into gene modules using coexpression analysis, and such modules were mapped to specific cell types in airway epithelia using public single-cell RNA-sequencing data. RESULTS: A higher number of DEGs for total IgE were identified in subjects with asthma (n = 1179 DEGs) than in all subjects (n = 631 DEGs). In subjects with asthma, DEGs were mapped to 11 gene modules. The top module for positive correlation with total IgE was mapped to myoepithelial and mucus secretory cells in lower airway epithelia and was regulated by IL-4, IL5, IL-13, and IL-33. Within this module, hub genes included CDH26, FETUB, NTRK2, CCBL1, CST1, and CST2. Furthermore, an enrichment analysis showed overrepresentation of genes in signaling pathways for synaptogenesis, IL-13, and ferroptosis, supporting interactions between interleukin- and acetylcholine-induced responses. CONCLUSIONS: Our findings for nasal epithelial gene expression support neuroimmune coregulation of total IgE in youth with asthma.

The effects of violence and related stress on asthma.

In the United States, people living in deprived urban areas and persons in certain minoritized groups are often exposed to violence and affected with asthma, and epidemiologic studies have shown a link between exposure to violence (ETV) and asthma throughout the lifespan. Indeed, ETV at the individual, intrafamilial and community levels has been linked to asthma in children and adults. In this review, we discuss the evidence for a causal relation between ETV and asthma, emphasizing findings published in the last five years. Interpretation of the available evidence is limited by variable quality of the assessment of ETV or asthma, potential recall and selection bias, inability to estimate the relative contribution of various types of violence to the observed associations, lack of objective biomarkers of asthma or asthma endotypes, and inconsistent consideration of potential confounders or modifiers of the ETV-asthma link. Despite such limitations, the aggregate evidence from studies conducted in different locations and populations suggests that ETV affects asthma and asthma outcomes, and that this is explained by direct physiologic effects of violence-related distress and indirect effects (e.g., through risky health behaviors or co-morbidities). Thus, large prospective studies with careful assessment of specific types of ETV, key covariates and comorbidities (including mental illness), and asthma are needed to advance this field. Such research efforts should not preclude screening for maltreatment in children with asthma and ETV-related depression and anxiety in adolescents and adults with asthma. Further, vigorous policies are needed to curtail violence, as such policies could benefit patients with asthma while saving lives.

Persistent cat ownership and asthma in a longitudinal study of Puerto Rican youth.

BACKGROUND: Epidemiologic studies have reported conflicting findings for cat or dog exposure and childhood asthma. No study has evaluated whether persistent pet exposure from early life to school age is associated with asthma or allergic sensitization in youth. OBJECTIVE: To evaluate whether persistent ownership of a cat or a dog throughout childhood is associated with asthma in Puerto Rican youth, a group disproportionately affected with asthma. METHODS: Prospective study of 384 youth who completed a baseline visit at ages 6 to 14 years and a second visit at ages 9 to 20 years. Persistent cat or dog ownership was defined as ownership of a cat or a dog in early life (during pregnancy or the first year of life) at either study visit (at school age). An allergen-specific IgE result was considered positive if more than or equal to 0.35 IU/mL. Logistic regression was used for the multivariable analysis of asthma and allergic sensitization. RESULTS: In an analysis adjusting for household income, family history of atopy, persistent overweight or obesity, a persistent unhealthy diet, the time interval between study visits, and other covariates, persistent cat ownership was significantly associated with 68% reduced odds of asthma (95% CI for odds ratio = 0.11-0.92) but not with any allergic sensitization or sensitization to cat allergen. In contrast, persistent dog ownership was not significantly associated with asthma or allergic sensitization. CONCLUSION: Among school-aged Puerto Rican youth followed for an average of 5 years, persistent cat ownership from early life to school age was inversely associated with asthma.

Low parental numeracy and severe asthma exacerbations in a prospective study of Puerto Rican youth.

BACKGROUND: Numeracy is the mathematical knowledge required to understand and act on instructions from health care providers. Whether persistently low parental numeracy is linked to childhood asthma exacerbations is unknown. OBJECTIVE: To evaluate whether low parental numeracy at 2 time points is associated with asthma exacerbations and worse lung function in Puerto Rican youth. METHODS: Prospective study of 225 youth with asthma in San Juan (PR) who participated in 2 visits approximately 5.3 years apart, with the first at ages 6 to 14 years and the second at ages 9 to 20 years. Parental numeracy was assessed with a modified version of the Asthma Numeracy Questionnaire (score range = 0-3 points), and persistently low parental numeracy was defined as a score less than or equal to 1 point at both visits. Asthma exacerbation outcomes included more than or equal to 1 emergency department (ED) visit, more than or equal to 1 hospitalization, and more than or equal to 1 severe exacerbation (≥1 ED visit or ≥1 hospitalization) for asthma in the year before the second visit. Spirometry was conducted using an EasyOne spirometer (NDD Medical Technologies, Andover, Massachusetts). RESULTS: In an analysis adjusting for age, sex, parental education, use of inhaled corticosteroids, and the time between study visits, persistently low parental numeracy was associated with more than or equal to 1 ED visit for asthma (odds ratio [ORs], 2.17; 95% confidence interval [CI], 1.10-4.26), more than or equal to 1 hospitalization for asthma (OR, 3.92; 95% CI, 1.42-10.84), and more than or equal to 1 severe asthma exacerbation (OR, 1.99; 95% CI, 1.01-3.87) in the year before the follow-up visit. Persistently low parental numeracy was not significantly associated with change in lung function measures. CONCLUSION: Persistently low parental numeracy is associated with asthma exacerbation outcomes in Puerto Rican youth.

Effect of vitamin D supplementation on total and allergen-specific IgE in children with asthma and low vitamin D levels.

BACKGROUND: Observational studies have yielded inconsistent findings for the relation between vitamin D level and total IgE or allergic sensitization. OBJECTIVE: To determine whether vitamin D supplementation reduces levels of total IgE and IgE to each of 2 common indoor allergens in children with asthma and low vitamin D levels. METHODS: Total IgE, IgE to Dermatophagoides pteronyssinus, and IgE to Blattella germanica were measured at the randomization and exit visits for 174 participants in the Vitamin D Kids Asthma Study, a multicenter, double-blind, randomized placebo-controlled trial of vitamin D3 supplementation (4000 IU/d) to prevent severe exacerbations in children with persistent asthma and vitamin D levels less than 30 ng/mL. Multivariable linear regression was used for the analysis of the effect of vitamin D supplementation on change in each IgE measure. RESULTS: Participants were followed for an average of 316 days. At the exit visit, more subjects in the vitamin D arm achieved a vitamin D level equal to or more than 30 ng/mL compared with those in the placebo arm (87% vs 30%; P < .001). In a multivariable analysis, vitamin D3 supplementation had no significant effect on change in total IgE, IgE to Dermatophagoides pteronyssinus, or IgE to Blattella germanica between the exit and randomization visits (eg, for log10 total IgE, ß = 0.007; 95% CI, -0.061 to 0.074; P = .85). CONCLUSIONS: Vitamin D supplementation, compared with placebo, has no significant effect on serum levels of total IgE, IgE to dust mite, or IgE to cockroach in children with asthma and low vitamin D levels.

Child maltreatment, anxiety and depression, and asthma among British adults in the UK Biobank.

BACKGROUND: Child maltreatment is associated with asthma in adults. We examined whether lifetime major depressive disorder (MDD) or lifetime generalised anxiety disorder (GAD) mediate an association between child maltreatment and current asthma among 81 105 British adults in the UK Biobank who completed a mental health survey and had complete data on child maltreatment, GAD, MDD, asthma and relevant covariates but no diagnosis of chronic obstructive pulmonary disease. METHODS: Child maltreatment was ascertained based on answers to the five questions in the Childhood Trauma Screener. Two mediators, lifetime MDD and GAD, were assessed based on the Composite International Diagnostic Interview Short Form. Current asthma was defined as physician-diagnosed asthma and wheeze or whistling in the chest in the previous year. Logistic regression was used for the multivariable analysis of child maltreatment and current asthma, and a mediation analysis was conducted to estimate the contributions of lifetime MDD and lifetime GAD to the child maltreatment-current asthma association. RESULTS: In a multivariable analysis, any child maltreatment was associated with asthma (adjusted OR 1.22, 95% CI 1.15-1.28; p<0.01). In a mediation analysis adjusted for household income, educational attainment, smoking status, pack-years of smoking and other covariates, lifetime GAD and lifetime MDD explained 21.8% and 32.5%, respectively, of the child maltreatment-current asthma association. Similar results were obtained after excluding current smokers and former smokers with ≥10 pack-years of smoking from the mediation analysis. CONCLUSION: Our findings suggest that GAD and MDD mediate an association between child maltreatment and asthma in adults, independently of smoking.

Violence-related distress and lung function in two longitudinal studies of youth.

BACKGROUND: Exposure to violence has been associated with lower lung function in cross-sectional studies. METHODS: We examined whether increasing violence-related distress over time is associated with worse lung function and worse asthma control or quality of life in a secondary analysis of a 48-week randomised clinical trial in 98 youth with asthma (aged 9-16 years) treated with low-dose inhaled corticosteroids (Vitamin D Kids Asthma Study (VDKA)). We then replicated our findings for lung function in a prospective study of 232 Puerto Rican youth followed for an average of 5.4 years. Violence-related distress was assessed using the Checklist of Children's Distress Symptoms (CCDS) scale. Our outcomes of interest were percent predicted lung function measures and (in VDKA only) asthma control (assessed using the Asthma Control Test) and asthma-related quality of life (assessed using the Pediatric Asthma Quality of Life Questionnaire (PAQLQ)). RESULTS: In a multivariable analysis in VDKA, each 1-point increment in CCDS score was associated with decrements of 3.27% in forced expiratory volume in 1 s (FEV1) % pred (95% CI -6.44- -0.22%; p=0.04), 2.65% in forced vital capacity (FVC) % pred (95% CI -4.86- -0.45%; p=0.02) and 0.30 points in the overall PAQLQ score (95% CI -0.50- -0.10 points; p<0.01). Similar findings for FEV1 and FVC were obtained in the prospective study of Puerto Rican youth. CONCLUSIONS: Our findings suggest that violence-related distress may worsen lung function and quality of life in youth with asthma (even those treated with low-dose inhaled corticosteroids), and further support policies to reduce exposure to violence among children in the USA and Puerto Rico.

The Dietary Inflammatory Index and asthma burden in children: A latent class analysis.

INTRODUCTION: Unbalanced dietary intake has been increasingly recognized as an important modifiable risk factor for asthma. In this study, we assessed whether a pro-inflammatory diet is associated with higher asthma burden in three steps: (1) identification of asthma latent classes (LC) based on symptoms, indoor exposures, and pulmonary function; (2) identification of risk factors associated with LC membership; and (3) estimation of the probabilities of LC membership with variation in DII. METHODS: A cross-sectional study on 415 children aged 5-14 years (266 with persistent asthma and 149 controls). LC analysis was performed in asthmatic children. The DII was calculated based on a semiquantitative food frequency questionnaire. Elastic net logistic regression was used to investigate whether increasing DII was associated with worse asthma burden. RESULTS: Two LCs were identified. Children in Class 1, "high burden," had higher symptom burden and worse lung function. Children in Class 2, "low burden," had lower symptom burden and less impaired lung function but were more subject to indoor exposures. DII was the only risk factor significantly associated with Class 1 membership. As the DII increased (from -4.0 to +4.0), the probability of Class 1 membership increased from 32% to 65% when compared with control group, whereas it increased from 41% to 72% when compared with Class 2. CONCLUSIONS: We identified two phenotypes of persistent asthma associated with different disease burden linked to indoor exposures. An increasing DII was associated with high-burden asthma, providing further evidence about the role of a pro-inflammatory diet in asthma morbidity.

Differential gene expression in nasal airway epithelium from overweight or obese youth with asthma.

BACKGROUND: The mechanisms underlying the known link between overweight/obesity and childhood asthma are unclear. We aimed to identify differentially expressed genes and pathways associated with obesity-related asthma through a transcriptomic analysis of nasal airway epithelium. METHODS: We compared the whole transcriptome in nasal airway epithelium of youth with overweight or obesity and asthma with that of youth of normal weight and asthma, using RNA sequencing data from a cohort of 235 Puerto Ricans aged 9-20 years (EVA-PR) and an independent cohort of 66 children aged 6-16 years in Pittsburgh (VDKA). Differential expression analysis adjusting for age, sex, sequencing plate number, and sample sorting protocol, and the first five principal components were performed independently in each cohort. Results from the two cohorts were combined in a transcriptome-wide meta-analysis. Gene enrichment and network analyses were performed on top genes. RESULTS: In the meta-analysis, 29 genes were associated with obesity-related asthma at an FDR-adjusted p <.05, including pro-inflammatory genes known to be differentially expressed in adipose tissue of obese subjects (e.g., CXCL11, CXCL10, and CXCL9) and several novel genes. Functional enrichment analyses showed that pathways for interferon signaling, and innate and adaptive immune responses were down-regulated in overweight/obese youth with asthma, while pathways related to ciliary structure or function were up-regulated. Upstream regulatory analysis predicted significant inhibition of the IRF7 pathway. Network analyses identified "hub" genes like GBP5 and SOCS1. CONCLUSION: Our transcriptome-wide analysis of nasal airway epithelium identified biologically plausible genes and pathways for obesity-related asthma in youth.

Persistent overweight or obesity, lung function, and asthma exacerbations in Puerto Rican youth.

BACKGROUND: Whether persistent overweight or obesity affects lung function or asthma morbidity in youth is unclear. OBJECTIVE: To evaluate overweight or obesity that persists between school age and adolescence and change in lung function and total immunoglobulin (Ig)E and severe asthma exacerbations in Puerto Rican youth. METHODS: Prospective study of 340 Puerto Rican youth assessed at 2 visits, the first at ages 6 to 14 years and the second at ages 9 to 20 years. Persistent overweight or obesity was defined as a body mass index z-score greater than or equal to 85th percentile at both visits. Outcomes of interest were change in percent predicted (%pred) lung function measures and total IgE between study visits and severe asthma exacerbations in the year before visit 2. Logistic or linear regression was used for multivariable analysis. RESULTS: In multivariable analysis, persistently overweight or obese subjects had changes in %pred forced expiratory volume in 1 second (FEV1) (ß = -5.07%; 95% confidence interval, -1.51% to -8.62%; P < .01) and %pred FEV1 to forced vital capacity (FVC) ratio (ß = -2.85%; 95% confidence interval, -0.18% to -5.51%; P = .04) which were lower than those observed in subjects with normal weight at both study visits (control subjects). Compared with control subjects, those who were persistently overweight or obese and those who became overweight or obese at visit 2 had increased odds of more than or equal to 1 severe asthma exacerbation in the year before visit 2. There was no significant association between persistent overweight or obesity and change in %pred FVC or total IgE (P > .20 for both instances). CONCLUSION: In a prospective study of Puerto Rican youth, persistently overweight or obese subjects had lower changes in FEV1 or FEV1 to FVC ratio and higher odds of severe asthma exacerbations than subjects of normal weight.

Urinary caffeine and caffeine metabolites, asthma, and lung function in a nationwide study of U.S. adults.

OBJECTIVE: Coffee intake has been inversely associated with asthma in adults. We examined the relation between urinary levels of caffeine or caffeine metabolites and asthma, lung function, and fractional exhaled nitric oxide (FeNO) in adults. METHODS: Cross-sectional study of 2,832 adults aged 18-79 years in the US National Health and Nutrition Examination Survey (NHANES). Multivariable logistic or linear regression was used for the analysis of urinary levels of caffeine or each of its three major metabolites (paraxanthine, theobromine, and theophylline) and current asthma, lung function, and FeNO. RESULTS: Subjects with urinary paraxanthine levels in the fourth quartile (Q4) had 53% lower odds of current asthma than those whose urinary paraxanthine levels were in the first quartile (Q1; 95% confidence = 0.22 to 1.00). Among never and former smokers, subjects with urinary theophylline levels above Q1 had 49% lower odds of current asthma than those whose urinary theophylline level was in Q1 (95% CI = 0.31 to 0.85). Among subjects without current asthma, each log10-unit increment in paraxanthine level was associated with a 0.83% increment in percent predicted (%pred) FEV1 and a 1.27% increment in %pred FVC, while each log10-unit in theophylline was associated with a 1.24% increment in %pred FVC. Neither urinary caffeine nor any urinary caffeine metabolite was associated with bronchodilator response or FeNO. CONCLUSIONS: Our findings suggest that two caffeine metabolites (theophylline and paraxanthine) may contribute to the previously reported inverse association between coffee intake and asthma in adults.

A genome-wide association study of severe asthma exacerbations in Latino children and adolescents.

Severe asthma exacerbations are a major cause of school absences and healthcare costs in children, particularly those in high-risk racial/ethnic groups.To identify susceptibility genes for severe asthma exacerbations in Latino children and adolescents, we conducted a meta-analysis of genome-wide association studies (GWAS) in 4010 Latino youth with asthma in four independent cohorts, including 1693 Puerto Ricans, 1019 Costa Ricans, 640 Mexicans, 256 Brazilians and 402 members of other Latino subgroups. We then conducted methylation quantitative trait locus, expression quantitative trait locus and expression quantitative trait methylation analyses to assess whether the top single nucleotide polymorphism (SNP) in the meta-analysis is linked to DNA methylation and gene expression in nasal (airway) epithelium in separate cohorts of Puerto Rican and Dutch children and adolescents.In the meta-analysis of GWAS, an SNP in FLJ22447 (rs2253681) was significantly associated with 1.55 increased odds of severe asthma exacerbation (95% CI 1.34-1.79, p=6.3×10-9). This SNP was significantly associated with DNA methylation of a CpG site (cg25024579) at the FLJ22447 locus, which was in turn associated with increased expression of KCNJ2-AS1 in nasal airway epithelium from Puerto Rican children and adolescents (ß=0.10, p=2.18×10-7).SNP rs2253681 was significantly associated with both DNA methylation of a cis-CpG in FLJ22447 and severe asthma exacerbations in Latino youth. This may be partly explained by changes in airway epithelial expression of a gene recently implicated in atopic asthma in Puerto Rican children and adolescents (KCNJ2-AS1).

Serum insulin-like growth factor-1, asthma, and lung function among British adults.

BACKGROUND: Insulin-like growth factor-1 (IGF-1) plays a key role in the pathogenesis of metabolic syndrome, which is in turn associated with asthma. Whether IGF-1 contributes to asthma causation or asthma severity is largely unknown. OBJECTIVE: To evaluate the relation between serum IGF-1 and asthma, asthma outcomes, and lung function in adults. METHODS: Cross-sectional study of 297,590 adults (aged 40-69 years) who participated in the United Kingdom Biobank, had no diagnosis of diabetes, and were not on insulin. Multivariable logistic or linear regression was used to analyze serum IGF-1 and physician-diagnosed asthma, current wheezing, asthma hospitalizations, and lung function measures (forced expiratory volume in 1 second [FEV1], forced vital capacity [FVC], and FEV1 to FVC ratio). RESULTS: Serum IGF-1 levels above the lowest quartile (Q1) were significantly associated with lower odds of asthma (adjusted odds ratio for fourth quartile [Q4] vs Q1 = 0.88; 95% confidence interval [CI], 0.85-0.91). Among the participants with asthma, IGF-1 levels above Q1 were significantly associated with lower odds of current wheezing (adjusted odds ratio for Q4 vs Q1 = 0.89; 95% CI, 0.83-0.96), but not with asthma hospitalizations. Serum IGF-1 was significantly and positively associated with FEV1 (b = 20.9 mL; 95% CI, 19.1-22.7) and FVC (b = 25.6 mL; 95% CI, 23.4-27.7), regardless of an asthma diagnosis; these associations were significant in men and women, with larger estimated effects in men. CONCLUSION: In a large study of British adults, higher serum IGF-1 levels were associated with lower odds of asthma and current wheezing and higher FEV1 and FVC. Our findings suggest potential beneficial effects of circulating IGF-1 on asthma and asthma outcomes in adults.

Testosterone-to-estradiol ratio and lung function in a prospective study of Puerto Rican youth.

BACKGROUND: Age- and sex-related differences in asthma may be due to changes in sex hormone levels. OBJECTIVE: To evaluate whether a change in free testosterone or free testosterone-to-estradiol ratio is associated with changes in lung function and eosinophils in the Puerto Rican youth. METHODS: We tested for the association between the change in sex hormone levels and change in lung function or change in eosinophils in a prospective study of 317 children (with and without asthma) followed up from ages 6 to 14 years to ages 10 to 20 years (146 females, 171 males) in San Juan, Puerto Rico. Serum levels of testosterone, estradiol, sex hormone-binding globulin, and progesterone were measured at 2 study visits, approximately 4.9 years apart. Using testosterone and sex hormone-binding globulin levels, we derived free testosterone and the free testosterone-to-estradiol ratio. Multivariable linear regression was used for the analysis of change in lung function and eosinophils, conducted separately by sex. RESULTS: In girls, each quartile increment in the free testosterone-to-estradiol ratio was associated with a 2.03% increment in percent predicted forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) between study visits. In males, each quartile increment in the free testosterone-to-estradiol ratio was associated with a 3.27% increment in percent predicted FEV1 and a 1.81% increment in percent predicted FEV1/FVC between study visits. In girls with asthma, an increased free testosterone-to-estradiol ratio was significantly associated with decreased eosinophils between visits (P=0.03). CONCLUSION: In Puerto Rican youth, increased free testosterone-to-estradiol ratio over time was associated with an increased FEV1/FVC in both sexes, and with an increased FEV1 in males.

Sex Steroid Hormones and Asthma in a Nationwide Study of U.S. Adults.

Rationale: Women have a higher burden of asthma than men. Although sex hormones may explain sex differences in asthma, their role is unclear.Objectives: To examine sex hormone levels and asthma in adults.Methods: Cross-sectional study of serum levels of free testosterone and estradiol and current asthma in 7,615 adults (3,953 men and 3,662 women) aged 18-79 years who participated in the 2013-2014 and 2015-2016 U.S. National Health and Nutrition Examination Survey. Logistic regression was used for the multivariable analysis of sex hormones and current asthma, which was conducted separately in women and men.Measurements and Main Results: Free testosterone levels in the fourth quartile were associated with lower odds of current asthma in women (odds ratio [OR] for the fourth quartile [Q4] vs. Q1, 0.56; 95% confidence interval [CI], 0.39-0.80). Given an interaction between obesity and sex hormones on current asthma, we stratified the analysis by obesity. In this analysis, elevated free testosterone (OR for Q4 vs. Q1, 0.59; 95% CI, 0.37-0.91) and estradiol (OR for Q4 vs. Q1, 0.43; 95% CI, 0.23-0.78) levels were associated with reduced odds of current asthma in obese women, and an elevated serum estradiol was associated with lower odds of current asthma in nonobese men (OR for Q4 vs. Q1, 0.44; 95% CI, 0.21-0.90).Conclusions: Our findings suggest that sex hormones play a role in known sex differences in asthma in adults. Moreover, our results suggest that obesity modifies the effects of sex hormones on asthma in adults.

Serum free testosterone and asthma, asthma hospitalisations and lung function in British adults.

OBJECTIVE: We examined the relation between serum-free testosterone and asthma, wheeze, asthma hospitalisations and lung function in older adults. DESIGN: Cross-sectional study. SETTING: UK. PARTICIPANTS: 256 419 adults aged 40 to 69 years, recruited from 2006 to 2010. MAIN OUTCOME MEASURES: Multivariable logistic or linear regression was used for the analysis of free testosterone and physician-diagnosed asthma, current wheeze, asthma hospitalisations and lung function measures, which was adjusted for serum estradiol, smoking status and other covariates. RESULTS: Free testosterone levels above the lowest quartile (Q1) were significantly associated with lower odds of asthma in both women (adjusted OR (aOR) for Q4 (the highest quartile) versus Q1=0.67, 95% CI=0.64 to 0.71) and men (aOR for Q4 versus Q1=0.87, 95% CI=0.82 to 0.91). Among subjects with asthma, free testosterone levels above Q1 were significantly associated with lower odds of current wheeze in women (aOR range=0.78 to 0.87), and free testosterone levels in Q4 were associated with lower odds of current wheeze in men (aOR for Q4 versus Q1=0.86, 95% CI=0.77 to 0.95). Among women with asthma, free testosterone levels in Q4 were also associated with lower odds of ≥1 asthma hospitalisation. Among men, free testosterone was positively associated with FEV1 and FVC. Among women, free testosterone was negatively and weakly associated with FVC. CONCLUSION: In a large study of British adults, elevated free testosterone levels are associated with lower odds of asthma and current wheeze in women and men, lower odds of asthma hospitalisations in women, and higher FEV1 and FVC in men. DISSEMINATION TO PARTICIPANTS, AND RELATED PATIENT AND PUBLIC COMMUNITIES: The results of the study will be linked to the UK Biobank website.

Indoor endotoxin, proximity to a major roadway, and severe asthma exacerbations among children in Puerto Rico.

BACKGROUND: Few studies have examined concurrent exposure to household endotoxin and traffic-related air pollution in relation to childhood asthma, yet both factors are associated with asthma outcomes. OBJECTIVE: To examine whether proximity to a major roadway (a traffic-related air pollution proxy) modifies the estimated effects of indoor endotoxin on asthma outcomes in children. METHODS: Cross-sectional study of 200 children with asthma (ages, 6-14 years) living in Puerto Rico. Residential distance to a major roadway was calculated as the distance from the participant's residential US census block centroid to the nearest major road. The outcomes of interest were severe asthma exacerbations, missed school days for asthma, atopy, lung function, and bronchodilator response (BDR). Logistic, linear, or negative binomial regression was used for the multivariable analysis. RESULTS: In the multivariable analysis, there was an interaction between indoor endotoxin and residential distance to a roadway on severe asthma exacerbations (P = .02) and BDR (P = .07). In an analysis stratified by distance to a roadway, each log10-unit increase in endotoxin was associated with 4.21 times increased odds of severe asthma exacerbations among children living within 499 m (the lower 3 quartiles of residential distance) to a road (95% confidence interval, 1.5-12.0). Among subjects living further than 499 m away from a roadway, each log10-unit increase in endotoxin was associated with reduced odds of severe asthma exacerbations (odds ratio, 0.03; 95% confidence interval, 0.001-0.67). Similar but less substantial findings were observed for BDR. CONCLUSION: Our findings suggest that residential proximity to a major road modifies the estimated effect of endotoxin on severe asthma exacerbations in children.

Effect of Vitamin D3 Supplementation on Severe Asthma Exacerbations in Children With Asthma and Low Vitamin D Levels: The VDKA Randomized Clinical Trial.

Importance: Severe asthma exacerbations cause significant morbidity and costs. Whether vitamin D3 supplementation reduces severe childhood asthma exacerbations is unclear. Objective: To determine whether vitamin D3 supplementation improves the time to a severe exacerbation in children with asthma and low vitamin D levels. Design, Setting, and Participants: The Vitamin D to Prevent Severe Asthma Exacerbations (VDKA) Study was a randomized, double-blind, placebo-controlled clinical trial of vitamin D3 supplementation to improve the time to severe exacerbations in high-risk children with asthma aged 6 to 16 years taking low-dose inhaled corticosteroids and with serum 25-hydroxyvitamin D levels less than 30 ng/mL. Participants were recruited from 7 US centers. Enrollment started in February 2016, with a goal of 400 participants; the trial was terminated early (March 2019) due to futility, and follow-up ended in September 2019. Interventions: Participants were randomized to vitamin D3, 4000 IU/d (n = 96), or placebo (n = 96) for 48 weeks and maintained with fluticasone propionate, 176 µg/d (6-11 years old), or 220 µg/d (12-16 years old). Main Outcomes and Measures: The primary outcome was the time to a severe asthma exacerbation. Secondary outcomes included the time to a viral-induced severe exacerbation, the proportion of participants in whom the dose of inhaled corticosteroid was reduced halfway through the trial, and the cumulative fluticasone dose during the trial. Results: Among 192 randomized participants (mean age, 9.8 years; 77 girls [40%]), 180 (93.8%) completed the trial. A total of 36 participants (37.5%) in the vitamin D3 group and 33 (34.4%) in the placebo group had 1 or more severe exacerbations. Compared with placebo, vitamin D3 supplementation did not significantly improve the time to a severe exacerbation: the mean time to exacerbation was 240 days in the vitamin D3 group vs 253 days in the placebo group (mean group difference, -13.1 days [95% CI, -42.6 to 16.4]; adjusted hazard ratio, 1.13 [95% CI, 0.69 to 1.85]; P = .63). Vitamin D3 supplementation, compared with placebo, likewise did not significantly improve the time to a viral-induced severe exacerbation, the proportion of participants whose dose of inhaled corticosteroid was reduced, or the cumulative fluticasone dose during the trial. Serious adverse events were similar in both groups (vitamin D3 group, n = 11; placebo group, n = 9). Conclusions and Relevance: Among children with persistent asthma and low vitamin D levels, vitamin D3 supplementation, compared with placebo, did not significantly improve the time to a severe asthma exacerbation. The findings do not support the use of vitamin D3 supplementation to prevent severe asthma exacerbations in this group of patients. Trial Registration: ClinicalTrials.gov Identifier: NCT02687815.