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

Conclusion

COPD was prevalent in this population of never-smokers aged 40 years and over. This finding highlights the significance of risk factors other than smoking in the development of COPD.

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Key Words

• BOLD
• LLN
• burden of obstructive lung disease
• lower limit of normal
• non-smokers
• prevalence
• spirometry

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MESH Headings

• Female
• Male
• Humans
• Adult
• Middle Aged
• Child
• Smokers
• Pulmonary Disease, Chronic Obstructive/diagnosis
• Pulmonary Disease, Chronic Obstructive/epidemiology
• Asthma
• Odds Ratio
• Australia/epidemiology

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Grants

• National Health and Medical Research Council (NHMRC) of Australia
• Thoracic Society of Australia and New Zealand
• Robert Pierce Grant-in-Aid for Indigenous Lung Health
• Air Liquide, AstraZeneca; GlaxoSmithKline; and Boehringer Ingelheim

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Respiratory Symptoms, Disease Burden, and Quality of Life in Australian Adults According to GOLD Spirometry Grades: Data from the BOLD Australia Study

Purpose

Population data on the burden of chronic obstructive pulmonary disease (COPD) are often based on patient-reported diagnoses of COPD, emphysema or chronic bronchitis, without spirometry. We aimed to investigate the relationship between health burden, quality of life and severity of airway obstruction in Australian adults aged ≥40 years.

Methods

We used data from the BOLD Australia study, which included randomly selected adults aged ≥40 years from six study sites to reflect the sociodemographic and geographic diversity of the Australian population (n = 3522). Participants with post-bronchodilator airflow limitation (ratio of forced expiratory volume in 1 second FEV1 to forced vital capacity <0.7) were grouped by GOLD spirometry grades 1-4. Quality of life was assessed with Short Form 12 (SF-12) Health Survey Questionnaire. Health burden was assessed as lost time off work or social activities, and healthcare utilization.

Results

Of the study sample, 2969 participants did not have airflow limitation, 294 (8.4%) were classified as GOLD Grade 1, 212 (6.0%) as GOLD 2 and 43 (1.2%) as GOLD 3-4. Participants with higher GOLD grades had more respiratory symptoms, more comorbidities and greater burden than those with lower GOLD grades. The scores of mental and physical subscales of SF-12 were lower, indicating worse quality of life, from the no airflow limitation group to the GOLD 3-4 group (P = 0.03 and P < 0.001, respectively).

Conclusion

Greater airflow limitation is associated with greater burden and poor quality of life. Interventions to prevent, or reduce the level of, airflow limitation will reduce the symptom burden and improve quality of life for patients.

Clinical characteristics of adults with self-reported diagnosed asthma and/or COPD: data from the BOLD Australia Study

Background

Diagnosis of asthma and chronic obstructive pulmonary disease (COPD) in the community is variable, often without spirometry. Some studies report that adults with both diagnostic labels (asthma+COPD) have worse health outcomes than those with asthma or COPD only, but data for Australian adults are limited. We investigated the relationship between clinical characteristics and self-reported diagnoses of asthma, COPD and both.

Method

We used data from the BOLD Australia study, which included randomly selected adults aged ≥40 years from six study sites. The BOLD questionnaires and spirometry test were used in all sites. Participants were grouped by self-reported diagnosis. Demographic and clinical characteristics and lung function were compared between groups.

Results

Of the study sample (n=3522), 336 reported asthma only, 172 reported COPD only, 77 reported asthma+COPD and 2937 reported neither. Fewer than half of participants with a COPD diagnosis (with or without asthma) had airflow limitation. Participants with asthma+COPD had more respiratory symptoms and greater airflow limitation than those with either diagnosis alone. Having asthma+COPD was independently associated with a higher probability of having clinically important breathlessness (modified Medical Research Council score ≥2) than asthma only (adjusted OR 3.44, 95% CI 1.86-6.33) or COPD only (adjusted OR 3.28, 95% CI 1.69-6.39). Airflow limitation (Global Initiative for Chronic Obstructive Lung Disease 2 or higher, using post-bronchodilator forced expiratory volume in 1 s/forced vital capacity ratio <0.7) was similar between asthma only and COPD only, but twice as prevalent in asthma+COPD (adjusted OR 2.18 and 2.58, respectively).

Conclusions

Adults with diagnoses of asthma+COPD have a higher symptom and disease burden than those with diagnoses of asthma only or COPD only. These patients should receive regular comprehensive reviews because of the substantially increased burden of having both diagnoses.

The Health Effects of 72 Hours of Simulated Wind Turbine Infrasound: A Double-Blind Randomized Crossover Study in Noise-Sensitive, Healthy Adults

BACKGROUND

Large electricity-generating wind turbines emit both audible sound and inaudible infrasound at very low frequencies that are outside of the normal human range of hearing. Sufferers of wind turbine syndrome (WTS) have attributed their ill-health and particularly their sleep disturbance to the signature pattern of infrasound. Critics have argued that these symptoms are psychological in origin and are attributable to nocebo effects.

OBJECTIVES

We aimed to test the effects of 72 h of infrasound (1.6-20 Hz at a sound level of ∼90 dB pk re 20μPa, simulating a wind turbine infrasound signature) exposure on human physiology, particularly sleep.

METHODS

We conducted a randomized double-blind triple-arm crossover laboratory-based study of 72 h exposure with a >10-d washout conducted in a noise-insulated sleep laboratory in the style of a studio apartment. The exposures were infrasound (∼90  dB pk), sham infrasound (same speakers not generating infrasound), and traffic noise exposure [active control; at a sound pressure level of 40-50 dB LAeq,night and 70 dB LAFmax transient maxima, night (2200 to 0700 hours)]. The following physiological and psychological measures and systems were tested for their sensitivity to infrasound: wake after sleep onset (WASO; primary outcome) and other measures of sleep physiology, wake electroencephalography, WTS symptoms, cardiovascular physiology, and neurobehavioral performance.

RESULTS

We randomized 37 noise-sensitive but otherwise healthy adults (18-72 years of age; 51% female) into the study before a COVID19-related public health order forced the study to close. WASO was not affected by infrasound compared with sham infrasound (-1.36 min; 95% CI: -6.60, 3.88, p=0.60) but was worsened by the active control traffic exposure compared with sham by 6.07 min (95% CI: 0.75, 11.39, p=0.02). Infrasound did not worsen any subjective or objective measures used.

DISCUSSION

Our findings did not support the idea that infrasound causes WTS. High level, but inaudible, infrasound did not appear to perturb any physiological or psychological measure tested in these study participants. https://doi.org/10.1289/EHP10757.

Risk factors and clinical characteristics of breathlessness in Australian adults: Data from the BOLD Australia study

BACKGROUND

Breathlessness is a common symptom related to a significant health burden. However, the association of breathlessness with clinical characteristics, especially objective pulmonary test results is scarce. We aimed to identify the characteristics independently associated with breathlessness in Australian adults.

METHOD

The analysis used data from BOLD Australia, a cross-sectional study that included randomly selected adults aged ≥40 years from six sites in Australia. Clinical characteristics and spirometry results were compared for breathlessness (modified Medical Research Council [mMRC] grade ≥2).

RESULTS

Among all respondents (n = 3321), 252 participants (7.6%) reported breathlessness. The main univariate associations were obesity, chronic respiratory diseases, heart diseases and being Indigenous Australians (odds ratios [ORs] = 2.78, 5.20, 3.77 and 4.38, respectively). Participants with breathlessness had lower pre-and post-bronchodilator lung function than those without. Impaired spirometry results including FVC or FEV1 below 80% predicted, or FEV1/FVC < LLN were independently associated with breathlessness (adjusted ORs = 2.66, 2.94 and 2.34, respectively).

CONCLUSIONS

Breathlessness is common among Australian adults and is independently associated with obesity, chronic respiratory diseases, heart diseases, being Indigenous Australians, and impaired spirometry. Multi-disciplinary assessment and comprehensive investigation is needed in clinical practice to address the many factors associated with breathlessness in the population.

Contribution of obesity to breathlessness in a large nationally representative sample of Australian adults

BACKGROUND AND OBJECTIVE

Breathlessness is prevalent and associated with medical consequences. Obesity is related to breathlessness. However, the magnitude of its contribution has not been clearly documented. This investigation aimed to determine the contribution of obesity to breathlessness by estimating the population attributable fraction (PAF) in a representative sample of Australian adults.

METHODS

A cross-sectional, nationally representative survey of Australian residents aged ≥18 years was conducted in October 2019. Breathlessness was defined as modified Medical Research Council (mMRC) dyspnoea scale grade ≥2. BMI was calculated from self-reported height and weight. Adjusted relative risks (aRRs) were estimated using a generalized linear model with Poisson distribution, adjusted for age group and/or participant-reported diagnosed illnesses. Adjusted PAFs were estimated using aRR and obesity prevalence in Australian adults.

RESULTS

Among those who completed the National Breathlessness Survey, 9769 participants (51.4% female) were included in the analysis; 28.1% of participants were obese. The prevalence of breathlessness was 9.54%. The aRR of obesity for breathlessness was 2.04, adjusted for age. Adjusting for various co-morbid conditions, the aRR was slightly attenuated to around 1.85-1.98. The PAF, adjusted only for age, was 24.6% (95% CI 20.1-29.1) and after further adjustment for co-morbid conditions, the PAF ranged from 21.1% to 23.6%. Obesity accounted for a higher proportion of breathlessness in women than in men.

CONCLUSION

Our results demonstrate that obesity accounts for around a quarter of breathlessness symptoms in Australian adults. This has important implications for health policy in light of the global trend in increasing obesity.

Ultrafine particle exposure and biomarkers of effect on small airways in children

The small size and large surface area of ultrafine particles (UFP) enhance their ability to deposit in the lung periphery and their reactivity. The Ultrafine Particles from Traffic Emissions and Children's Health (UPTECH) cross-sectional study was conducted in 8-11-year-old schoolchildren attending 25 primary (elementary) schools, randomly selected from the Brisbane Metropolitan Area, Queensland, Australia. Main study findings outlined indirect evidence of distal airway deposition (raised C reactive protein) but as yet, there is no direct evidence in the literature of effects of UFP exposure on peripheral airway function. We present further UPTECH study data from two sensitive peripheral airway function tests, Oscillometry and Multiple Breath Nitrogen Washout (MBNW), performed in 577 and 627 children (88% and 96% of UPTECH study cohort) respectively: mean(SD) age 10.1(0.9) years, 46% male, with 50% atopy and 14% current asthma. Bayesian generalised linear mixed effects regression models were used to estimate the effect of UFP particle number count (PNC) exposure on key oscillometry (airway resistance, (Rrs), and reactance, (Xrs)) and MBNW (lung clearance index, (LCI) and functional residual capacity, (FRC)) indices. We adjusted for age, sex, and height, and potential confounders including socio-economic disadvantage, PM_2.5 and NO₂ exposure. All models contained an interaction term between UFP PNC exposure and atopy, allowing estimation of the effect of exposure on non-atopic and atopic students. Increasing UFP PNC was associated with greater lung stiffness as evidenced by a decrease in Xrs [mean (95% credible interval) -1.63 (-3.36 to -0.05)%] per 1000#.cm^-3]. It was also associated with greater lung stiffness (decrease in Xrs) in atopic subjects across all models [mean change ranging from -2.06 to -2.40% per 1000#.cm^-3]. A paradoxical positive effect was observed for Rrs across all models [mean change ranging from -1.55 to -1.70% per 1000#.cm^-3] (decreases in Rrs indicating an increase in airway calibre), which was present for both atopic and non-atopic subjects. No effects on MBNW indices were observed. In conclusion, a modest detrimental effect of UFP on peripheral airway function among atopic subjects, as assessed by respiratory system reactance, was observed extending the main UPTECH study findings which reported a positive association with a biomarker for systemic inflammation, C-reactive protein (CRP). Further studies are warranted to explore the pathophysiological mechanisms underlying increased respiratory stiffness, and whether it persists through to adolescence and adulthood.

The prevalence of SARS-CoV-2 antibodies in quarantine workers and high-risk communities in Vietnam

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A low prevalence (2%) of SARS-CoV-2 antibodies was found among quarantine workers.

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A low prevalence of SARS-CoV-2 antibodies was found in communities with COVID-19.

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Vietnam had controlled the COVID-19 pandemic until mid-2021.

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This study preceded the widespread outbreak in Vietnam in mid-2021.

Objective

The aim of this study was to determine the seroprevalence of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) antibodies in high-risk communities and quarantine workers in Vietnam.

Methods

The prevalence of SARS-CoV-2 antibodies was measured in household contacts, close contacts, community members, and migrant workers from two sub-communes in which COVID-19 outbreaks occurred in early 2021: Bac Ma 1 and Tien. The prevalence of SARS-CoV-2 antibodies was also evaluated among quarantine workers at two facilities responsible for quarantining of contacts of COVID-19 cases.

Results

Among 2069 participants from the two sub-communes, six individuals (0.3%) had detectable SARS-CoV-2 antibodies despite no history of COVID-19. This included one Vietnamese migrant worker, two community members, two household contacts, and one close contact of known COVID-19 cases. Among 50 workers at two COVID-19 quarantine facilities, including 15 health care workers (HCWs), one of the HCWs tested positive for SARS-CoV-2 antibodies (1/50, 2.0%) despite no known disease.

Conclusion

The prevalence of SARS-CoV-2 antibodies was low in Vietnamese ‘hotspots’, suggesting limited community transmission.

The Indoor Environment and Otitis Media among Australian Children: A National Cross-Sectional Study

The association between the indoor environment and lifetime prevalence of otitis media (OM) in Australian children was assessed. We analysed data from a cross-sectional study of children, aged 7–11 years, performed in twelve Australian cities during 2007–2008. The main outcome was a parental report of their child’s diagnosis with OM by a doctor. Information on the indoor environment (energy sources used for heating, cooling, and cooking, pets, and second-hand smoke exposure), in the first year of life and at present, was collected from parents by a questionnaire. Multi-level logistic regression models were used to adjust for individual- and area-level confounders. Our analysis comprised 2872 children (51% female, mean age: 10.0 (SD 1.2)). Of those, 1097 (39%) were reported to have OM. Exposure to gas heating in the first year of life was significantly associated with higher odds of OM in adjusted models (OR:1.22; 95% CI: 1.00,1.47), as was current exposure to reverse-cycle air conditioning (OR: 1.52, 95% CI: 1.27,1.82). Ownership of a cat or dog at any time was also associated with high odds of OM (OR: 1.50; 95% CI: 1.17,1.92). No other significant associations were observed. In this national study of Australian children, indoor environmental exposures associated with the lifetime prevalence of OM were gas heating, reverse-cycle air conditioning and pet ownership. Exposures in both early life and later childhood may both play a role in OM.

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.

Normative values for bronchodilator responses measured by oscillometry were derived. Responsiveness related to clinical factors and baseline function. Reactance was more sensitive in detecting bronchodilator response than spirometry mild airways disease.https://bit.ly/3wtWVeV

Prevalence of chronic obstructive pulmonary disease with breathlessness in Australia: weighted using the 2016 Australian census

Access to up-to-date Australian disease prevalence estimates assists health services and consumer organisations to plan and allocate resources. The Burden of Obstructive Lung Disease study was conducted between 2006 and 2012 and provided chronic obstructive pulmonary disease (COPD) (post-bronchodilator airflow limitation) prevalence estimates weighted to the 2006 Australian census. Using the 2016 Australian census, an updated prevalence estimate of all COPD is 8.30% (95% confidence interval = 6.59%-10.01%) for adults aged 40 or more years in Australia and includes 2.52% with mild breathlessness, 0.99% with moderate breathlessness and 0.91% with severe breathlessness.

Prevalence and burden of breathlessness in Australian adults: The National Breathlessness Survey-a cross-sectional web-based population survey

BACKGROUND AND OBJECTIVE

Chronic respiratory symptoms (in particular, breathlessness and cough) can cause physical, social and emotional distress, and may indicate the presence of an underlying disease that presages future poor health outcomes. Our aim was to investigate the burden of breathlessness in Australian adults, including breathlessness that may be undiagnosed, unlabelled or untreated.

METHODS

The National Breathlessness Survey was a cross-sectional, web-based survey conducted in October 2019. Australian adults were randomly selected from a large web-based survey panel with recruitment stratified by age-group, gender and state of residence according to national population data. The main outcome measures were modified Medical Research Council (mMRC) dyspnoea scale, EuroQol visual analog scale, Dyspnoea-12 score and 4-item Patient Health Questionnaire (PHQ-4).

RESULTS

Among all respondents (n = 10,072; 51.1% female; median age group 40-49 years), 9.5% reported clinically important breathlessness (mMRC dyspnoea grade ≥ 2, 2 = 'I walk slower than people of the same age on the level because of breathlessness or have to stop for breath when walking at my own pace on the level'). Among those with clinically important breathlessness, 49.1% rated their general health as fair or poor and 44.2% had at least moderate depression or anxiety symptoms (PHQ ≥ 6) but over half (50.8%) did not report a current respiratory or heart condition diagnosis.

CONCLUSION

Breathlessness is common among Australian adults, and is associated with a substantial burden of ill health, including among people without a diagnosed respiratory or heart condition. The extent of underdiagnosis of these conditions or alternative causes of breathlessness requires further investigation.

Undiagnosed and Misdiagnosed Chronic Obstructive Pulmonary Disease: Data from the BOLD Australia Study

PURPOSE

Spirometry is necessary to confirm COPD, but many patients are diagnosed based on clinical presentation and/or chest x-ray. There are also those who do not present to primary care for case finding and remain undiagnosed. We aimed to identify: (a) factors that are associated with undiagnosed COPD; and (b) factors that are associated with a potential misdiagnosis of COPD.

PATIENTS AND METHODS

This analysis used data from the Burden of Obstructive Lung Disease (BOLD), a cross-sectional study of community dwelling adults randomly selected from six study sites, chosen to provide a representative sample of the Australian population (n= 3357). Participants were grouped by COPD diagnostic criteria based on spirometry and self-reported diagnosis. Odds ratios for predictors of undiagnosed and misdiagnosed were estimated using logistic regression.

RESULTS

Of the BOLD Australia sample, 1.8% had confirmed COPD, of whom only half self-reported a diagnosis of COPD. A further 6.9% probably had COPD, but were undiagnosed. The priority target population for case finding of undiagnosed COPD was aged ≥60 years (particularly those ≥75 years), with wheezing, shortness of breath and a body mass index (BMI) <25kg/m2. The priority target population for identifying and reviewing misdiagnosed COPD was aged <60 years, female, with no wheezing and a BMI ≥25kg/m2.

CONCLUSION

Challenges continue in accurately diagnosing COPD and greater efforts are needed to identify undiagnosed and misdiagnosed individuals to ensure an accurate diagnosis and the initiation of appropriate management in order to reduce the burden of COPD.

A national cross-sectional study of exposure to outdoor nitrogen dioxide and aeroallergen sensitization in Australian children aged 7-11 years

The prevalence of allergic diseases in Australian children is high, but few studies have assessed the potential role of outdoor air pollution in allergic sensitization. We investigated the association between outdoor air pollution and the prevalence of aeroallergen sensitization in a national cross-sectional study of Australian children aged 7-11 years. Children were recruited from 55 participating schools in 12 Australian cities during 2007-2008. Parents completed a detailed (70-item) questionnaire. Outdoor nitrogen dioxide (NO₂), as a proxy for exposure to traffic-related emissions, was estimated using measurements from regulatory monitors near each school and a national land-use regression (LUR) model. Three averaging periods were assessed, using information on duration of residence at the address, including lifetime, previous (lifetime, excluding the last year), and recent (the last year only). The LUR model was used as an additional source of recent exposure estimates at school and home addresses. Skin prick tests (SPTs) were performed to measure sensitization to eight common aeroallergens. Multilevel logistic regression estimated the association between NO₂ and sensitization (by individual allergens, indoor and outdoor allergens, and all allergens combined), after adjustment for individual- and area-level covariates. In total, 2226 children had a completed questionnaire and SPT. The prevalence of sensitization to any allergen was 44.4%. Sensitization to house dust mites (HDMs) was the most common (36.1%), while sensitization to Aspergillus was the least common (3.4%). Measured mean (±s.d.) NO₂ exposure was between 9 (±2.9) ppb and 9.5 (±3.2) ppb, depending on the averaging period. An IQR (4 ppb) increase in measured previous NO₂ exposure was associated with greater odds of sensitization to HDMs (OR: 1.21, 95% CI: 1.01-1.43, P = 0.035). We found evidence of an association between relatively low outdoor NO₂ concentrations and sensitization to HDMs, but not other aeroallergens, in Australian children aged 7-11 years.

Experimentally determined deposition of ambient urban ultrafine particles in the respiratory tract of children

A critical element of the risk assessment of exposure to airborne ambient ultrafine particles (UFP) is the quantification of respiratory tract deposition (RTD) of the particles, which is intrinsically challenging, particularly at the population scale. In this study, we used a recently proposed method to experimentally determine the RTD of urban UFP in a large group of children exposed to these particles in a school setting in Brisbane, Australia. Children are one of the most susceptible population groups; However, little is known about the deposition of UFP from urban traffic in their airways. In order to advance the knowledge in this field, the objectives of this study were: to determine the deposition of ambient urbane UFP in large number children, to catergorize the source of inhaled UFPs and hence to assess the contribution of air pollution sources to the deposition. RTD was measured in children aged 8-11 at primary schools using a flow-through chamber bag system. First, the inhaled and exhaled air was separated; then the particle number size distribution and particle number concentration were measured. The sources of inhaled UFP were categorized according to their particle number size distribution by a K means cluster technique. A total of 128 children from five schools performed the RTD measurement. The mean total deposition fraction of urban UFP in all children was 0.59 ± 0.10. Inhaled UFP were categorized into two groups: traffic and urban background, with the GMD of corresponding particle number size distribution of 20 nm and 40 nm, respectively. The total deposition fraction (mean ± SD) of UFP from these two groups was 0.68 ± 0.09 for traffic and 0.55 ± 0.08 for urban background respectively. This is the first study in which RTD was measured in a large group of children inhaling real urban UFP. First, we proved that this novel method can indeed be applied easily and quickly to a large group of people. Second, we quantified the RTD of children, thus providing an important input to the risk assessment for exposure to UFP.

Experimentally determined deposition of ambient urban ultrafine particles in the respiratory tract of children

A critical element of the risk assessment of exposure to airborne ambient ultrafine particles (UFP) is the quantification of respiratory tract deposition (RTD) of the particles, which is intrinsically challenging, particularly at the population scale. In this study, we used a recently proposed method to experimentally determine the RTD of urban UFP in a large group of children exposed to these particles in a school setting in Brisbane, Australia. Children are one of the most susceptible population groups; However, little is known about the deposition of UFP from urban traffic in their airways. In order to advance the knowledge in this field, the objectives of this study were: to determine the deposition of ambient urbane UFP in large number children, to catergorize the source of inhaled UFPs and hence to assess the contribution of air pollution sources to the deposition. RTD was measured in children aged 8-11 at primary schools using a flow-through chamber bag system. First, the inhaled and exhaled air was separated; then the particle number size distribution and particle number concentration were measured. The sources of inhaled UFP were categorized according to their particle number size distribution by a K means cluster technique. A total of 128 children from five schools performed the RTD measurement. The mean total deposition fraction of urban UFP in all children was 0.59 ± 0.10. Inhaled UFP were categorized into two groups: traffic and urban background, with the GMD of corresponding particle number size distribution of 20 nm and 40 nm, respectively. The total deposition fraction (mean ± SD) of UFP from these two groups was 0.68 ± 0.09 for traffic and 0.55 ± 0.08 for urban background respectively. This is the first study in which RTD was measured in a large group of children inhaling real urban UFP. First, we proved that this novel method can indeed be applied easily and quickly to a large group of people. Second, we quantified the RTD of children, thus providing an important input to the risk assessment for exposure to UFP.

Psychological and Medical Characteristics Associated with Non-Adherence to Prescribed Daily Inhaled Corticosteroid

Medication non-adherence is associated with sub-optimal asthma control. Identification of medical and psychological characteristics associated with non-adherence is important to enable a targeted and personalized approach when working with patients and for the development of interventions to improve patient outcomes by improving medication adherence. We enrolled adults who had diagnosed asthma and who were prescribed daily inhaled corticosteroid medication. We used published and validated instruments to measure medical characteristics including asthma features, practical asthma knowledge and perceived involvement in care and psychological characteristics including anxiety, depression, optimism, and personality traits, to assess the relationship with medication non-adherence. A total of 126 participants provided data, with 64 (50.8%) of the participants identified as non-adherent. Multivariate analyses showed that younger age, high neuroticism scores and a previous asthma hospital admission were associated with non-adherence. Interestingly, depression was associated with a lower risk of non-adherence. This study showed that a personalized medicine approach would include interventions targeting those who are younger, who have been in hospital for asthma and who rate high on the neuroticism personality trait. Given the availability of effective medications for asthma, better understanding of the characteristics associated with non-adherence is important to enhance optimal self-management.

Health System Costs of Treating Latent Tuberculosis Infection With Four Months of Rifampin Versus Nine Months of Isoniazid in Different Settings

BACKGROUND

Four months of rifampin treatment for latent tuberculosis infection is safer, has superior treatment completion rates, and is as effective as 9 months of isoniazid. However, daily medication costs are higher for a 4-month rifampin regimen than a 9-month isoniazid regimen.

OBJECTIVE

To compare health care use and associated costs of 4 months of rifampin and 9 months of isoniazid.

DESIGN

Health system cost comparison using all health care activities recorded during 2 randomized clinical trials. (ClinicalTrials.gov: NCT00931736 and NCT00170209).

SETTING

High-income countries (Australia, Canada, Saudi Arabia, and South Korea), middle-income countries (Brazil and Indonesia), and African countries (Benin, Ghana, and Guinea).

PARTICIPANTS

Adults and children with clinical or epidemiologic factors associated with increased risk for developing tuberculosis that warranted treatment for latent tuberculosis infection.

MEASUREMENTS

Health system costs per participant.

RESULTS

A total of 6012 adults and 829 children were included. In both adults and children, greater health system use and higher costs were observed with 9 months of isoniazid than with 4 months of rifampin. In adults, the ratios of costs of 4 months of rifampin versus 9 months of isoniazid were 0.76 (95% CI, 0.70 to 0.82) in high-income countries, 0.90 (CI, 0.85 to 0.96) in middle-income countries, and 0.80 (CI, 0.78 to 0.81) in African countries. Similar findings were observed in the pediatric population.

LIMITATION

Costs may have been overestimated because the trial protocol required a minimum number of follow-up visits, although fewer than recommended by many authoritative guidelines.

CONCLUSION

A 4-month rifampin regimen was safer and less expensive than 9 months of isoniazid in all settings. This regimen could be adopted by tuberculosis programs in many countries as first-line therapy for latent tuberculosis infection.

PRIMARY FUNDING SOURCE

Canadian Institutes of Health Research.

Tree pollen exposure is associated with reduced lung function in children

BACKGROUND

Allergic disease is a recognized global epidemic and a significant cause of ill health and poor quality of life. The prevalence of pollen allergy is high throughout the world, and pollen exposure itself plays a role in emergency department presentations and hospitalizations for asthma. Lung function and airway inflammation are important measures of asthma activity and control.

OBJECTIVE

To examine associations between exposure to multiple pollen types and lung function and markers of airway inflammation at 8 and 14 years of age, and to explore potential modification by residential greenness.

METHODS

A cohort of high-risk children living in Sydney, Australia had spirometry and fractional exhaled nitric oxide (FeNO) measured at 8 and 14 years of age. Ambient pollen concentration on the day of lung function measurement and up to three days prior was used as the exposure measure. Residential greenness was derived from satellite imagery. We modelled the association between six pollen types and lung function and FeNO. We also assessed modifying effects of residential greenness.

RESULTS

Casuarina, cypress and Pinus pollen in the air the day before measurement and 3 days prior respectively, were associated with reduced lung function in 8-year-olds. The pollen exposures were associated with decreases in FEV₁ and FVC; however, the FEV₁ /FVC ratio was not affected. Effect modification by greenness was not observed due to loss of power.

CONCLUSIONS & CLINICAL RELEVANCE

Airborne tree pollen of cypress, Casuarina and Pinus and not grass in some regions may be detrimental to childhood lung function.

Weight Gain Trajectories from Birth to Adolescence and Cardiometabolic Status in Adolescence

OBJECTIVE

To assess the influence of the trajectory of weight gain from birth to adolescence on cardiovascular and metabolic risk. We studied childhood body mass index (BMI) trajectories from birth to age 14 years and cardiometabolic risk factors at age 14 years.

STUDY DESIGN

In total, 410 children with weight and height measurements were assessed from birth throughout childhood, from the Childhood Asthma Prevention Study, a prospective community-based cohort. BMI trajectory groups were determined by latent basis growth mixture models. Of these subjects, 190 had detailed cardiometabolic risk factors assessed at age 14 years.

RESULTS

Three BMI trajectory groups were identified; normal BMI, "early rising" excess BMI from 2 years, and "late rising" excess BMI from 5 years. Differences were found between normal and excess BMI in children at 14 years of age. In addition, children with an early rising BMI trajectory had statistically significantly higher central adiposity and a more atherogenic lipoprotein profile at age 14 years than children with a late rising BMI trajectory (P < .05). No differences between BMI trajectory groups in vascular structure or function was identified at age 14 years.

CONCLUSIONS

Earlier onset of an elevated BMI trajectory persisting from birth to age 14 years results in an unfavorable cardiometabolic risk profile at age 14 years, including central adiposity and more atherogenic lipoproteins, independent of achieved BMI.

Early and late childhood telomere length predict subclinical atherosclerosis at age 14 yrs. - The CardioCAPS study

INTRODUCTION

Carotid Intima Media Thickness (CIMT) is a marker of subclinical atherosclerosis, associated with cardiovascular risk in adults. Telomere length (TL) is a marker of cellular ageing. We sought to determine whether telomere length in early childhood and/or at 14-years is associated with CIMT in adolescence, in a community-based cohort study.

METHODS

118 children had TL measured at mean age 3.6-years and 165 children had TL and CIMT, measured at 14-years, from the community-based Childhood Asthma Prevention Study.

RESULTS

TL in early childhood was significantly inversely associated with CIMT at 14 years, p = 0.04. TL in teenage life was also significantly inversely associated with CIMT at 14 years, p = 0.03. This latter association was no longer significant, however, after adjusting for early life TL.

CONCLUSION

TL measured in early childhood and adolescence is significantly associated with CIMT at 14-years, suggesting that telomere length is a biological marker or even early determinant of late cardiovascular risk.

The Australian Child Health and Air Pollution Study (ACHAPS): A national population-based cross-sectional study of long-term exposure to outdoor air pollution, asthma, and lung function

Most studies of long-term air pollution exposure and children's respiratory health have been performed in urban locations with moderate pollution levels. We assessed the effect of outdoor nitrogen dioxide (NO₂), as a proxy for urban air pollution, on current asthma and lung function in Australia, a low-pollution setting. We undertook a national population-based cross-sectional study of children aged 7-11 years living in 12 Australian cities. We collected information on asthma symptoms from parents via questionnaire and measured children's lung function (forced expiratory volume in 1 s [FEV₁], forced vital capacity [FVC]) and fractional exhaled nitric oxide [Fe_NO]). We estimated recent NO₂ exposure (last 12 months) using monitors near each child's school, and used a satellite-based land-use regression (LUR) model to estimate NO₂ at each child's school and home. Our analysis comprised 2630 children, among whom the prevalence of current asthma was 14.9%. Mean (±SD) NO₂ exposure was 8.8 ppb (±3.2) and 8.8 ppb (±2.3) for monitor- and LUR-based estimates, respectively. Mean percent predicted post-bronchodilator FEV₁ and FVC were 101.7% (±10.5) and 98.8% (±10.5), respectively. The geometric mean Fe_NO concentration was 9.4 ppb (±7.1). An IQR increase in NO₂ (4.0 ppb) was significantly associated with increased odds of having current asthma; odds ratios (ORs) were 1.24 (95% CI: 1.08, 1.43) and 1.54 (95% CI: 1.26, 1.87) for monitor- and LUR-based estimates, respectively. Increased NO₂ exposure was significantly associated with decreased percent predicted FEV₁ (-1.35 percentage points [95% CI: -2.21, -0.49]) and FVC (-1.19 percentage points [95% CI: -2.04, -0.35], and an increase in Fe_NO of 71% (95% CI: 38%, 112%). Exposure to outdoor NO₂ was associated with adverse respiratory health effects in this population-based sample of Australian children. The relatively low NO₂ levels at which these effects were observed highlight the potential benefits of continuous exposure reduction.