Daily Respiratory Research Analysis
Three high-impact studies advance respiratory health: a Thorax case-crossover analysis links ultrafine particle exposure to increased pediatric asthma admissions; a population-based cohort from Ontario (The Journal of Infectious Diseases) details post-pandemic disruptions in pediatric respiratory virus hospitalizations; and a JAMA Network Open cohort shows race-neutral spirometry equations better identify lung function decline in Black patients.
Summary
Three high-impact studies advance respiratory health: a Thorax case-crossover analysis links ultrafine particle exposure to increased pediatric asthma admissions; a population-based cohort from Ontario (The Journal of Infectious Diseases) details post-pandemic disruptions in pediatric respiratory virus hospitalizations; and a JAMA Network Open cohort shows race-neutral spirometry equations better identify lung function decline in Black patients.
Research Themes
- Air pollution and pediatric asthma risk
- Post-pandemic pediatric respiratory virus epidemiology
- Race-neutral lung function interpretation
Selected Articles
1. Short-term exposure to ultrafine particles and asthma hospital admissions in children in Copenhagen, Denmark.
Using a time-stratified case-crossover design with 15,903 pediatric admissions, an interquartile range increase in ultrafine particles was linked to higher asthma hospitalizations, peaking at 2-day exposure windows (RR 1.17). Associations persisted after adjusting for PM2.5, indicating an independent effect of UFP.
Impact: Provides robust, policy-relevant evidence that short-term UFP exposure triggers pediatric asthma admissions, supporting regulation and monitoring of UFP beyond PM2.5.
Clinical Implications: Clinicians should counsel families of high-risk children on exposure mitigation during high-UFP days; public health systems should integrate UFP monitoring and consider real-time alerts, school/transport policies, and indoor air interventions.
Key Findings
- An IQR increase in UFP was associated with increased pediatric asthma admissions, strongest at 2-day exposure windows (RR 1.17, 95% CI 1.09–1.25).
- The UFP–asthma association remained after adjustment for PM2.5, suggesting an independent effect of ultrafine particles.
- Findings were consistent across socioeconomic and prior health status strata in a low-exposure urban setting.
Methodological Strengths
- Time-stratified case-crossover design controlling for time-invariant confounding within individuals
- Long monitoring period (2002–2018) with centralized urban background UFP measurements and registry-based outcomes
Limitations
- Single-site exposure monitoring may introduce spatial exposure misclassification
- Abstract does not report co-pollutant results beyond PM2.5 or effect modification details
Future Directions: Evaluate UFP composition-specific toxicity, personal exposure metrics, and effectiveness of mitigation (filtration, traffic policies) in reducing asthma exacerbations.
BACKGROUND: Ultrafine particles (UFP; <0.1 µm in diameter) are not regulated or commonly monitored but may be harmful to human health, particularly for children. In this study, we aimed to examine the association between short-term exposure to UFP and asthma hospital admissions in children. METHODS: Daily UFP concentrations (2002-2018) were monitored at an urban background station in Copenhagen, Denmark. Asthma hospital admissions, demographic and socioeconomic information of children (0-18 years) were obtained from registries. A case-crossover design was applied to estimate the association between hospital admissions and up to 6-day UFP exposure windows for all children, and stratified by age, sex, family income, mother's education, prior asthma or prior respiratory infection. RESULTS: We observed 15 903 asthma hospital admissions in total. An IQR increase in UFP was significantly associated with asthma hospital admissions, strongest at 2-day exposure windows (risk ratio (RR): 1.17 (95% CI: 1.09, 1.25)). These associations remained unchanged when adjusting for particulate matter <2.5 µm in diameter (PM CONCLUSIONS: In this large study in a low-exposure setting, we find that short-term exposure to UFP can trigger asthma hospital admissions in children, independently of associations with PM
2. Pediatric Acute Respiratory Virus Hospitalizations: A Population-Based Cohort Study, 2017-2024.
In a cohort covering ~2.7 million children per year, ARI hospitalizations plummeted in 2020/21, rebounded in 2021/22, and surged out-of-season in 2022/23, driven by RSV and HMPV. COVID-19 contributed minimally to pediatric ARI admissions. Seasonality largely normalized by 2023/24, but future stability remains uncertain.
Impact: Sets a comprehensive, population-level benchmark for post-pandemic pediatric respiratory virus burden, informing surge capacity, vaccination strategy, and timing of prophylaxis (e.g., RSV).
Clinical Implications: Hospitals should plan flexible surge capacity and stock prophylaxis/antivirals based on shifting seasonality; clinicians should anticipate older age distribution and adjust testing and triage protocols.
Key Findings
- RSV admissions in 2022/23 (n=4701) greatly exceeded pre-pandemic seasons (1969–2357), indicating an out-of-season surge.
- HMPV admissions also surged (377 vs 93–127 pre-pandemic), while influenza remained largely absent until later.
- COVID-19 contributed minimally to pediatric ARI admissions overall, especially among children <5 years; seasonality nearly resumed in 2023/24.
Methodological Strengths
- Province-wide, population-based cohort with linked administrative and clinical data
- Use of Poisson models to estimate expected post-pandemic admissions with adjusted rate ratios
Limitations
- Administrative data may undercapture mild community ARIs
- Causal drivers (e.g., immunity debt, behavioral shifts) cannot be disentangled observationally
Future Directions: Model the interplay of immunity debt, birth cohorts, and prophylaxis/vaccination to forecast pediatric ARI seasons; evaluate targeted RSV/HMPV interventions.
BACKGROUND: Coronavirus disease 2019 (COVID-19) mitigation measures resulted in widespread disruptions to respiratory viruses. The objective of this study was to compare observed and expected pediatric viral acute respiratory infection (ARI)-related hospitalizations, and the characteristics of admitted children, postpandemic. METHODS: Total and virus-specific ARI-related hospitalization rates were determined using a population-based cohort of youth <18 years in Ontario, Canada between July 2017 and June 2024. Sociodemographic and clinical characteristics were identified from linked administrative data. Expected weekly postpandemic age- and sex-specific admission rates were estimated using Poisson regression; adjusted rate ratios (RRs) and 95% confidence intervals (CIs) were reported. RESULTS: This cohort included approximately 2.7 million youth per year. There was a sharp reduction in ARIs in 2020/2021, followed by a moderate return in 2021/2022; influenza remained mostly absent (n = 168). An out of season persistence and overwhelming ARI burden occurred in 2022/2023, particularly for RSV (n = 4701 admissions vs 1969-2357 prepandemic) and human metapneumovirus (n = 377 vs 93-127). Overall, more older children (mean age, 38.9-42.8 vs 37.2-37.9 months prepandemic) and fewer males were admitted postpandemic; males were the only group with lower than expected 2022/2023 admissions (RR, 0.63; 95% CI, .57-.70 for all ARIs). COVID-19-related admissions contributed minimally to ARI-related hospitalizations overall, particularly among <5 year olds. Prepandemic seasonality appears to nearly have resumed in 2023/2024. CONCLUSIONS: Postpandemic disruptions in multiple ARIs substantially influenced the intensity, timing, and characteristics of children seeking health care. Although 2023/2024 was more typical, it is not yet clear when-or if-prepandemic ARI seasonality will resume. LAY SUMMARY: Substantial, unprecedented changes in several common childhood respiratory viruses occurred in each season following the COVID-19 pandemic, drastically impacting the timing and magnitude of demands placed upon the pediatric health care system, as well as the characteristics of children seeking care.
3. Lung Function Trajectory Using Race-Specific vs Race-Neutral Global Lung Function Initiative Coefficients.
Among 24,662 adults with repeated spirometry, 19.2% of Black patients were recategorized from normal to abnormal by race-neutral GLI Global; their FEV1 decline resembled those consistently abnormal. In White patients, 15% shifted from abnormal to normal without worse trajectories. Race-neutral interpretation may better flag pathology in Black patients.
Impact: Directly informs ongoing transitions away from race-based spirometry, with longitudinal evidence that race-neutral equations better align classification with disease trajectory in Black patients.
Clinical Implications: Pulmonary labs should evaluate adoption of GLI Global; clinicians should anticipate reclassification, particularly among Black patients, and integrate trajectories into diagnostic/eligibility decisions.
Key Findings
- 19.2% of Black patients were recategorized from normal to abnormal by GLI Global; their FEV1 decline matched those with consistently abnormal spirometry.
- 15.0% of White patients were recategorized from abnormal to normal by GLI Global without worse FEV1 trajectories.
- Race-neutral equations may improve detection of clinically meaningful decline in Black patients.
Methodological Strengths
- Large longitudinal cohort with repeated spirometry over a median 2.6 years
- Direct comparison of z-score classifications and trajectories under two reference equations
Limitations
- Single-center cohort with predominantly White population may limit generalizability
- Residual confounding (e.g., comorbidities, exposures) cannot be fully excluded
Future Directions: Validate GLI Global across diverse populations and settings; assess impacts on diagnosis, disability determinations, and clinical trial eligibility.
IMPORTANCE: The use of race-based coefficients in pulmonary function testing has led to the recent development of the race-neutral Global Lung Function Initiative (GLI) reference equation (hereafter GLI Global). The performance of GLI Global in comparison to race-adjusted coefficients (hereafter GLI 2012) has not been well characterized. OBJECTIVE: To compare the implications of GLI 2012 vs GLI Global reference equations for lung function trajectory. DESIGN, SETTING, AND PARTICIPANTS: This cohort study at Massachusetts General Hospital analyzed data of patients aged 18 to 95 years who completed spirometry testing between January 1, 1997, and December 31, 2020. Data analysis was performed from January 2023 to November 2024. EXPOSURES: GLI Global and GLI 2012 reference equations to define lung function. MAIN OUTCOMES AND MEASURES: Proportion of patients with recategorized lung function (FEV1 and FVC) based on the 2 reference equations and their lung function trajectory over time. Lung function metrics included forced expiratory volume in the first second of expiration (FEV1), forced vital capacity (FVC), and FEV1 to FVC ratio. The z scores for FEV1 and FVC were calculated using the GLI 2012 and GLI Global reference equations, with a score lower than -1.64 considered abnormal. Patients were categorized into 1 of 4 groups based on their z scores: normal to normal (normal z score on both equations); abnormal to normal (abnormal z score based on GLI 2012 equations but normal based on the GLI Global equation); normal to abnormal (normal z score on GLI 2012 equations but abnormal on the GLI Global equation); and abnormal to abnormal (abnormal z score on both equations). RESULTS: The sample included a total of 24 662 patients (988 Black [4.0%] and 22 297 White [90.4%] patients; 13 108 women [53.2%]) with a mean (SD) age of 57.6 (15.7) years who completed a median (IQR) of 3.0 (2.0-5.0) sets of spirometry over a median (IQR) of 2.6 (0.8-6.6) years between 1997 and 2020. Among Black patients, 190 (19.2%) had either their FEV1 or FVC recategorized from normal to abnormal using the GLI Global reference equation. The subset of Black patients whose lung function was recategorized from normal to abnormal exhibited FEV1 decline (-2.06%; 95% CI, -3.47% to -0.64%; P = .56) that was similar to decline in Black patients whose lung function was characterized as abnormal (-1.89%; 95% CI, -2.58% to -1.19%; P = .84) using both the GLI Global and GLI 2012 reference equations. Among White patients, 3348 (15.0%) had either their FEV1 or FVC recategorized from abnormal to normal using the GLI Global equation. FEV1 decline in these patients (-1.82%; 95% CI, -2.55% to -1.08%; P = .70) was similar to the decline in White patients with normal spirometry (-1.97%; 95% CI, -2.26% to -1.69%; P = .70) regardless of the reference equation used. Patterns in FVC trajectory among both Black and White participants were not consistent among participants whose spirometry was recategorized between normal and abnormal compared with those whose spirometry remained normal or remained abnormal regardless of the reference equation used. CONCLUSIONS AND RELEVANCE: This cohort study found that Black patients whose lung function was recategorized from normal to abnormal using the GLI Global reference equation exhibited FEV1 decline similar to that in Black patients whose lung function was classified as abnormal regardless of which equation was used. This finding suggests that a race-neutral approach to spirometry interpretation may allow a more accurate identification of lung pathology in Black patients.