Prevalence and burden of difficult-to-treat and severe asthma in Australia: A national population survey.

BACKGROUND AND OBJECTIVE: Most evidence about difficult-to-treat and severe asthma (DTTA) comes from clinical trials and registries. We aimed to identify people with DTTA from a large nationally representative asthma population and describe their characteristics and healthcare utilization compared with people whose asthma was not 'difficult-to-treat'. METHODS: We conducted a cross-sectional survey of Australians aged ≥18 years with current asthma from large web-based survey panels. Enrolment was stratified by gender, age-group and state/territory based on national population data for people with asthma. Difficult-to-treat or severe asthma was defined by poor symptom control, exacerbations and/or oral corticosteroid/biologic use despite medium/high-dose inhaled therapy. Outcomes included exacerbations, healthcare utilization, multimorbidity, quality of life and coronavirus disease of 2019 (COVID-19)-related behaviour. Weighted data were analysed using SAS version 9.4. RESULTS: The survey was conducted in February-March 2021. The weighted sample comprised 6048 adults with current asthma (average age 47.3 ± SD 18.1 years, 59.9% female), with 1313 (21.7%) satisfying ≥1 DTTA criteria. Of these, 50.4% had very poorly controlled symptoms (Asthma Control Test ≤15), 36.2% were current smokers, and 85.4% had ≥1 additional chronic condition, most commonly anxiety/depression. More than twice as many participants with DTTA versus non-DTTA had ≥1 urgent general practitioner (GP) visit (61.4% vs. 27.5%, OR 4.8 [4.2-5.5, p < 0.0001]), or ≥1 emergency room visit (41.9% vs. 17.9%, OR 3.8 [3.3-4.4, p < 0.0001]) in the previous 12 months. CONCLUSION: Our findings emphasize the burden of uncontrolled symptoms, current smoking, multimorbidity and healthcare utilization in people with DTTA in the community, who may be under-represented in registries or clinical trials.

COPD in Never-Smokers: BOLD Australia Study.

Purpose: Tobacco smoking is the major risk factor for COPD, and it is common for other risk factors in never-smokers to be overlooked. We examined the prevalence of COPD among never-smokers in Australia and identified associated risk factors. Methods: We used data from the Australia Burden of Obstructive Lung Disease (BOLD) study, a cross-section of people aged ≥40 years from six sites. Participants completed interviews and post-bronchodilator spirometry. COPD was primarily defined as an FEV1/FVC ratio <0.70 and secondarily as the ratio less than the lower limit of normal (LLN). Results: The prevalence of COPD in the 1656 never-smokers who completed the study was 10.5% (95% CI: 9.1-12.1%) [ratio

Normal limits for oscillometric bronchodilator responses and relationships with clinical factors.

INTRODUCTION: We aimed to determine normal thresholds for positive bronchodilator responses for oscillometry in an Australian general population sample aged ≥40 years, to guide clinical interpretation. We also examined relationships between bronchodilator responses and respiratory symptoms, asthma diagnosis, smoking and baseline lung function. METHODS: Subjects recruited from Sydney, Melbourne and Busselton, Australia, underwent measurements of spirometry, resistance (R rs6 ) and reactance (X rs6 ) at 6 Hz, before and after inhalation of salbutamol 200 µg. Respiratory symptoms and/or medication use, asthma diagnosis, and smoking were recorded. Threshold bronchodilator responses were defined as the fifth percentile of decrease in R rs6 and 95th percentile increase in X rs6 in a healthy subgroup. RESULTS: Of 1318 participants, 1145 (570 female) were analysed. The lower threshold for ΔR rs6 was -1.38 cmH2O·s·L-1 (-30.0% or -1.42 Z-scores) and upper threshold for ΔX rs6 was 0.57 cmH2O·s·L-1 (1.36 Z-scores). Respiratory symptoms and/or medication use, asthma diagnosis, and smoking all predicted bronchodilator response, as did baseline oscillometry and spirometry. When categorised into clinically relevant groups according to those predictors, ΔX rs6 was more sensitive than spirometry in smokers without current asthma or chronic obstructive pulmonary disease (COPD), ∼20% having a positive response. Using absolute or Z-score change provided similar prevalences of responsiveness, except in COPD, in which responsiveness measured by absolute change was twice that for Z-score. DISCUSSION: This study describes normative thresholds for bronchodilator responses in oscillometry parameters, including intra-breath parameters, as determined by absolute, relative and Z-score changes. Positive bronchodilator response by oscillometry correlated with clinical factors and baseline function, which may inform the clinical interpretation of oscillometry.

Characteristics in Stages of Change and Decisional Balance among Smokers: The Burden of Obstructive Lung Diseases (BOLD)-Australia Study.

Smoking cessation remains a health promotion target. Applying the Transtheoretical Model to Australian Burden of Obstructive Lung Diseases (BOLD) data, we examined differences in stages of change (SoC) and readiness to quit decisional behaviours. Factors were identified likely to influence readiness of smokers, ≥40 years old, to quit. Analysis was restricted to current smokers classified to one of three stages: pre-contemplation (PC), contemplation (C) or preparation (P) to quit. Their ability to balance positive and negative consequences was measured using decisional balance. Among 314 smokers, 43.0% females and 60.8% overweight/obese, the distribution of SoC was: 38.1% PC, 38.3% C and 23.5% P. Overweight/obesity was associated with readiness to quit in stages C and P and there were more negative than positive attitudes towards smoking in those stages. Males were significantly heavier smokers in PC and C stages. Females used smoking cessation medication more frequently in PC stage, were more embarrassed about smoking and had greater negative reinforcements from smoking. Age started smoking and factors related to smoking history were associated with readiness to quit and increased the odds of being in stage C or P. An overweight/obese smoker was likely to be contemplating or preparing to quit. In these stages, smokers have more negative attitudes toward smoking. Starting smoking later, taking advice on cessation from health providers and using quit medications indicate increased readiness to quit. Evaluating these factors in smokers and developing cessation gain-framed messages may prove useful to healthcare providers.

Childhood fish oil supplementation modifies associations between traffic related air pollution and allergic sensitisation.

BACKGROUND: Studies of potential adverse effects of traffic related air pollution (TRAP) on allergic disease have had mixed findings. Nutritional studies to examine whether fish oil supplementation may protect against development of allergic disease through their anti-inflammatory actions have also had mixed findings. Extremely few studies to date have considered whether air pollution and dietary factors such as fish oil intake may interact, which was the rationale for this study. METHODS: We conducted a secondary analysis of the Childhood Asthma Prevention Study (CAPS) birth cohort, where children were randomised to fish oil supplementation or placebo from early life to age 5 years. We examined interactions between supplementation and TRAP (using weighted road density at place of residence as our measure of traffic related air pollution exposure) with allergic disease and lung function outcomes at age 5 and 8 years. RESULTS: Outcome information was available on approximately 400 children (~ 70% of the original birth cohort). Statistically significant interactions between fish oil supplementation and TRAP were seen for house dust mite (HDM), inhalant and all-allergen skin prick tests (SPTs) and for HDM-specific interleukin-5 response at age 5. Adjusting for relevant confounders, relative risks (RRs) for positive HDM SPT were RR 1.74 (95% CI 1.22-2.48) per 100 m local road or 33.3 m of motorway within 50 m of the home for those randomised to the control group and 1.03 (0.76-1.41) for those randomised to receive the fish oil supplement. The risk differential was highest in an analysis restricted to those who did not change address between ages 5 and 8 years. In this sub-group, supplementation also protected against the effect of traffic exposure on pre-bronchodilator FEV1/FVC ratio. CONCLUSIONS: Results suggest that fish oil supplementation may protect against pro-allergic sensitisation effects of TRAP exposure. Strengths of this analysis are that supplementation was randomised and independent of TRAP exposure, however, findings need to be confirmed in a larger experimental study with the interaction investigated as a primary hypothesis, potentially also exploring epigenetic mechanisms. More generally, studies of adverse health effects of air pollution may benefit from considering potential effect modification by diet and other factors. TRIAL REGISTRATION: Australia New Zealand Clinical Trial Registry. www.anzctr.org.au Registration: ACTRN12605000042640 , Date: 26th July 2005. Retrospectively registered, trial commenced prior to registry availability.

Prevalence of airflow obstruction and reduced forced vital capacity in an Aboriginal Australian population: The cross-sectional BOLD study.

BACKGROUND AND OBJECTIVE: Mortality and hospital separation data suggest a higher burden of chronic obstructive pulmonary disease (COPD) in indigenous than non-indigenous subpopulations of high-income countries. This study sought to accurately measure the true prevalence of post-bronchodilator airflow obstruction and forced vital capacity reduction in representative samples of Indigenous and non-Indigenous Australians. METHODS: This study applies cross-sectional population-based survey of Aboriginal and non-Indigenous residents of the Kimberley region of Western Australia aged 40 years or older, following the international Burden Of Lung Disease (BOLD) protocol. Quality-controlled spirometry was conducted before and after bronchodilator. COPD was defined as Global initiative for chronic Obstructive Lung Disease (GOLD) Stage 2 and above (post-bronchodilator forced expiratory volume in 1 s/forced vital capacity (FEV1 /FVC) ratio <0.7 and FEV1 < 80% predicted). RESULTS: Complete data were available for 704 participants. The prevalence of COPD, adjusted for age, gender and body weight in Aboriginal participants (7.2%, 95% confidence interval (CI) 3.9 to 10.4) was similar to that seen in non-Indigenous Kimberley participants (8.2%, 95% CI 5.7 to 10.7) and non-Indigenous residents of the remainder of Australia (7.1%, 95% CI 6.1 to 8.0). The prevalence of low FVC (<80% predicted) was substantially higher in Aboriginal compared with non-Indigenous participants (74.0%, 95% CI 69.1 to 78.8, vs 9.7%, 95% CI 7.1 to 12.4). CONCLUSIONS: Low FVC, rather than airflow obstruction, characterizes the impact of chronic lung disease previously attributed to COPD in this population subject to significant social and economic disadvantage. Environmental risk factors other than smoking as well as developmental factors must be considered. These findings require further investigation and have implications for future prevention of chronic lung disease in similar populations.

Assessing the performance of two lung age equations on the Australian population: using data from the cross-sectional BOLD-Australia study.

INTRODUCTION: Lung age, a simple concept for patients to grasp, is frequently used as an aid in smoking cessation programs. Lung age equations should be continuously updated and should be made relevant for target populations. We observed how new lung age equations developed for Australian populations performed when utilizing the Burden of Obstructive Lung Disease (BOLD)-Australia dataset compared to more commonly used equations. METHODS: Data from a cross-sectional population study of noninstitutionalized Australians aged ≥40 years with analysis restricted to Caucasians <75 years. Lung age calculated using equations developed by Newbury et al. and Morris and Temple was compared with chronological age by smoking status and within smoking status. RESULTS: There were 2,793 participants with a mean age of 57 (±10 SD) years. More than half (52%) ever smoked, and 10.4% were current smokers. Prevalence of chronic obstructive pulmonary disease stage I or higher was 13.4% (95% confidence interval = 12.2, 14.7). For both genders, newer Newbury equations estimated lung ages significantly higher than actual age across all smoking groups (p < .05). Morris and Temple equations resulted in lung age estimates significantly lower than chronological age for nonsmokers (p < .05) but no difference among current smokers. Both equations showed exposure to smoking had lung ages higher than never-smokers (p < .001). Lung age also increased with increased pack-years. CONCLUSIONS: This supports the use of updated equations suited to the population of interest. The Australian Newbury equations performed well in the BOLD-Australia dataset, providing more meaningful lung age profile compared to chronological age among smokers. Using equations not developed or ideally suited for our population is likely to produce misleading results.

Respiratory health effects of exposure to low-NOx unflued gas heaters in the classroom: a double-blind, cluster-randomized, crossover study.

BACKGROUND: There are long-standing concerns about adverse effects of gas appliances on respiratory health. However, the potential adverse effect of low-NOx (nitrogen oxide) unflued gas heaters on children's health has not been assessed. OBJECTIVES: Our goal was to compare the respiratory health effects and air quality consequences of exposure to low-NOx unflued gas heaters with exposure to non-indoor-air-emitting flued gas heaters in school classrooms. METHODS: We conducted a double-blind, cluster-randomized, crossover study in 400 primary school students attending 22 schools in New South Wales, Australia. Children measured their lung function and recorded symptoms and medication use twice daily. Nitrogen dioxide (NO2) and formaldehyde concentrations were measured in classrooms using passive diffusion badges. RESULTS: NO2 concentrations were, on average, 1.8 times higher [95% confidence interval (CI), 1.6-2.1] and formaldehyde concentrations were, on average, 9.4 ppb higher (95% CI, 5.7-13.1) during exposure to unflued gas versus flued gas heaters. Exposure to the unflued gas heaters was associated with increased cough reported in the evening [odds ratio (OR) = 1.16; 95% CI, 1.01-1.34] and wheeze reported in the morning (OR = 1.38; 95% CI, 1.04-1.83). The association with wheeze was greater in atopic subjects. There was no evidence of an adverse effect on lung function. CONCLUSIONS: We conclude that classroom exposure to low-NOx unflued gas heaters causes increased respiratory symptoms, particularly in atopic children, but is not associated with significant decrements in lung function. It is important to seek alternative sources of heating that do not have adverse effects on health.

The association of comorbid anxiety and depression with asthma-related quality of life and symptom perception in adults.

BACKGROUND AND OBJECTIVE: There are limited data on the association and interaction between anxiety and depression comorbidity and asthma-related quality of life (AQOL) and symptom perception. This study evaluated these associations in patients subsequent to an emergency department (ED) visit for asthma. METHODS: This was a cross-sectional study of 110 (38 male) adult asthma patients (mean age 42 years), who had visited an ED in the previous 18 months. Participants completed the hospital anxiety and depression scale, measures of AQOL and the asthma symptom checklist. RESULTS: Depression symptoms independently showed a significant negative association with AQOL after controlling for depression/anxiety, age, gender, smoking status and ED visits in the previous 12 months (ED-12). Overall, anxiety and depression symptoms accounted for 28.3% of the variance in AQOL. Greater anxiety was associated with increased perception of asthma-specific panic-fear and hyperventilation symptoms during an asthma attack, irrespective of depression status. Categorical analyses of groups of patients, differentiated by psychometric properties on the hospital anxiety and depression scale (anxiety vs normal, anxiety and depression vs normal depression) confirmed most results. However, for the anxiety group there was a significant association with the AQOL domains of emotional functioning and response to environmental stimuli, after controlling for depression symptoms. CONCLUSIONS: The negative association of depression symptom scores with AQOL and of anxiety with increased panic-fear and hyperventilation symptoms suggests a potential role for interventions addressing this psychological comorbidity, in order to improve AQOL.

Occupational asthma in New South Wales (NSW): a population-based study.

BACKGROUND: The proportion of asthma in adults that is due to occupational exposures is not known. AIM: To examine the contribution of workplace exposures to the development of asthma in adults in New South Wales (NSW) in a cross sectional, population-based study. METHODS: A randomly selected population of 5,331 18- to 49-year olds completed and returned a mailed questionnaire (response rate 37%). In adult-onset asthmatics we examined the association of asthma with reported exposure, within 1 year of asthma onset, to a list of occupations and exposures known to be at risk for occupational asthma (high-risk jobs and exposures). RESULTS: Among 910 subjects (18%) with asthma, 383 (7%) subjects reported adult-onset disease. After adjusting for sex, age and smoking, working in any high-risk job or exposure at the time of asthma onset was significantly associated with adult-onset asthma (OR 1.51, 95% CI 1.19-1.92). The population attributable risk (PAR) of adult-onset asthma for either a high-risk job or an exposure was 9.5%. Sudden onset, irritant or reactive airways dysfunction syndrome type exposures were associated with adult-onset asthma (OR 4.65, 95% CI 1.64-13.2). The PAR of adult-onset asthma for these exposures was 0.2%. CONCLUSION: Reported adult onset of asthma is common and occupational exposures may be associated with 9.5% of prevalent cases of adult-onset asthma in NSW.