Is short-term exposure to grass pollen adversely associated with lung function and airway inflammation in the community?

Acute exposure to pollen and airway inflammation in adolescents

INTRODUCTION

Pollen exposure is known to exacerbate allergic asthma and allergic rhinitis symptoms, yet few studies have investigated if exposure to pollen affects lung function or airway inflammation in healthy children.

METHODS

We evaluated the extent to which higher pollen exposure was associated with differences in airway inflammation and lung function among 490 early adolescent participants (mean age of 12.9 years) in Project Viva, a prebirth cohort based in Massachusetts. We obtained regional daily total pollen counts, including tree, grass, and weed pollen, from a Rotorod pollen counter. We evaluated associations of 3- and 7-day moving averages of pollen with fractional exhaled nitric oxide (FeNO) and lung function using linear regression models and evaluated the linearity of associations with penalized splines. We tested if associations of pollen with FeNO and lung function were modified by current asthma diagnosis, history of allergic rhinitis, aeroallergen sensitivity, temperature, precipitation, and air pollution.

RESULTS

Three- and 7-day median pollen concentrations were 19.0 grains/m3 (IQR: 73.4) and 20.9 grains/m3 (IQR: 89.7). In main models, higher concentrations of total pollen over the preceding 3 and 7 days were associated with a 4.6% (95% CI: 0.1,9.2) and 7.4% (95% CI: 0.9,14.3) higher FeNO per IQR of pollen, respectively. We did not find associations of pollen with lung function in main models. Asthma, allergic rhinitis, precipitation, and air pollution (nitrogen dioxide and ozone) modified associations of pollen with lung function (Pinteraction < 0.1), while temperature, sex, and aeroallergen sensitization did not.

CONCLUSION

Short-term exposure to pollen was associated with higher FeNO in early adolescents, even in the absence of allergic sensitization and asthma.

Association of asthma exacerbations with paper mulberry (Broussenetia papyrifera) pollen in Islamabad: An observational study

Background

Although the role of airborne plant pollen in causing allergic rhinitis has been established, the association of concentrations of paper mulberry (Broussenetia papyrifera) pollens in the air and incidence of asthma exacerbations has not, despite an observed increase in the number of asthma patients attending physician clinics and hospital Accident and Emergency (A&E) Departments during the paper mulberry pollen season. We aimed to assess the association between paper mulberry pollen concentrations (typically peaking in March each year) and asthma exacerbations in the city of Islamabad.

Methods

We used three approaches to investigate the correlation of paper mulberry pollen concentration with asthma exacerbations: A retrospective analysis of historical records (2000-2019) of asthma exacerbations of patients from the Allergy and Asthma Institute, Pakistan (n = 284), an analysis of daily nebulisations in patients attending the A&E Department of the Pakistan Institute of Medical Sciences (March 2020 to July 2021), a prospective peak expiratory flow rate (PEFR) diary from participants (n = 40) with or without asthma and with or without paper mulberry sensitisation. We examined associations between pollen data and asthma exacerbations using Pearson correlation.

Results

We found a strong positive correlation between mean paper mulberry pollen counts and clinical records of asthma exacerbations in patients sensitised to paper mulberry (Pearson correlation coefficient (r) = 0.86; P < 0.001), but not in non-sensitised patients (r = 0.32; P = 0.3). There was a moderate positive correlation between monthly nebulisation counts and pollen counts (r = 0.56; P = 0.03), and a strong negative correlation between percent predicted PEFR and pollen counts in sensitised asthma patients (r = -0.72, P < 0.001). However, these correlations were of low magnitude in the non-sensitised asthma (r = -0.16; P < 0.001) and sensitised non-asthma (r = -0.28; P < 0.001) groups.

Conclusions

Our three approaches to analysis all showed an association between high paper mulberry pollen concentration in Islamabad and asthma exacerbations. Predicting pollen peaks could enable alerts and mobilise strategies to proactively manage these peaks of asthma exacerbations.

A Review of the Role of Pollen in COVID-19 Infection

There is current interest in the role of ambient pollen in the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2 or COVID-19) infection risk. The aim of this review is to summarise studies published up until January 2023 investigating the relationship between airborne pollen and the risk of COVID-19 infection. We found conflicting evidence, with some studies showing that pollen may increase the risk of COVID-19 infection by acting as a carrier, while others showed that pollen may reduce the risk by acting as an inhibiting factor. A few studies reported no evidence of an association between pollen and the risk of infection. A major limiting factor of this research is not being able to determine whether pollen contributed to the susceptibility to infection or just the expression of symptoms. Hence, more research is needed to better understand this highly complex relationship. Future investigations should consider individual and sociodemographic factors as potential effect modifiers when investigating these associations. This knowledge will help to identify targeted interventions.

Greenspace and children's lung function in China: A cross-sectional study between 2013 and 2015

This study aims to investigate how surrounding greenspace density and proximity were associated with children's lung function. Between 2013 and 2015, spirometry and a parental survey were performed with children from four primary schools in two Chinese cities. Forced expiratory volume in 1 s (FEV₁, L), forced vital capacity (FVC, L), peak expiratory flow rate (PEF, L/s), and forced expiratory flow at 25 % (FEF₂₅, L/s) and 75 % (FEF₇₅, L/s) of FVC were measured. Outdoor surrounding greenspace index incorporated residential, school and commuting greenness and was weighted using assumed daytime hours spent at home and school. Residential proximity to greenspace index was defined as walking distance to nearest park. A total of 913 children (48.7 % female) were included. Overall, an interquartile range (IQR) increase in outdoor surrounding greenspace was associated with decreased FVC (0.06 L, 95%CI 0.01-0.11), but increased FEV₁/FVC (2.03, 1.13-3.04), PEF (0.26 L/s, 0.13-0.39), and FEF₂₅ (0.30 L/s, 0.17-0.42). Residential proximity to greenspace was associated with increased FEV₁ (0.05 L, 0.02-0.08) and FVC (0.04 L, 0.01-0.07) per IQR decrease in distance. Protective effect was significant for children whose parents were less educated and those living in higher road density areas, though interactions were not significant. Structural equation modeling showed that higher level of surrounding greenspace was associated with lower ambient air pollution and in turn with better lung function. Greenspace density and proximity could influence children's lung function differently.

Grass pollen exposure is associated with higher readmission rates for pediatric asthma

BACKGROUND

Pediatric asthma hospital readmission is a burden on the individual and costly for Australian hospitals. Grass pollen's role, a known trigger for asthma admissions, is unexamined in readmissions. We examined the association between grass pollen and pediatric asthma readmission.

METHODS

The Victorian Admitted Episodes Dataset was used to identify all primary admissions with a principal diagnosis of asthma in children aged 2-18 years between 1997 and 2009. Readmissions were defined as subsequent admissions within 28 days of index admission discharge. Generalized additive models were used to assess associations between readmission, grass pollen season, and daily grass pollen counts, lagged and cumulative. Models were further stratified by sex and age group.

RESULTS

Mean daily readmission was higher during grass pollen season than other times of the year, incidence rate ratio (IRR) 1.44 (95% CI, 1.03, 2.02) and for children aged 2-5 years, IRR 1.99 (1.26, 3.14). Same day grass pollen was nonlinearly associated with daily readmission for the 13-18 age group between 110 and 256 grains/m³ , p < .01. Lag 2 grass pollen was nonlinearly associated with daily readmissions overall (p = .03), boys (p = .01), and younger age groups 2-5 (p = .02) and 6-12 (p < .001).

CONCLUSIONS

Grass pollen exposure was associated with higher readmission rates for pediatric asthma. Treatment plans prior to discharge could be implemented to reduce the likelihood of readmission by younger children during the pollen season.

The role of short-term grass pollen exposure in food skin-prick test reactivity, food allergy, and eczema flares in children

BACKGROUND

While the relationship between pollen and respiratory allergies is well-documented, the role of short-term pollen exposure in food allergy and eczema flares has not previously been explored. We aimed to investigate these associations in a population-based sample of children.

METHODS

We investigated 1- (n = 1108) and 6-year-old (n = 675) children in the grass pollen season from the HealthNuts cohort. Grass pollen concentrations were considered on the day of testing (lag 0), up to three days before (lag 1-lag 3) and cumulatively (lag 0-3). Associations between grass pollen and food skin-prick test reactivity (SPT ≥ 2 mm at age 1 year and ≥ 3 mm at age 6 years), eczema flares, challenge-confirmed food allergy, reaction threshold to oral food challenges (OFC), and serum food-specific IgE levels were analyzed using either logistic or quantile regression models. Atopy and family history of allergic disease were considered as potent effect modifiers.

RESULTS

Grass pollen at lag 0-3 (every 20 grains/m³ increase) was associated with an up to 1.2-fold increased odds of food SPT reactivity and eczema flares in 6-year-olds. In 1-year-olds, the associations were only observed for peanut in those with a family history of food allergy. Increasing grass pollen concentrations were associated with a lower reaction threshold to OFC and higher serum IgE levels in peanut-allergic 1-year-olds only.

CONCLUSION

Increasing grass pollen concentration was associated with increased risk of food SPT reactivity and eczema flares in children. The associations in peanut-allergic infants may be related to immune activation and/or peanut and grass pollen cross-reactivity leading to a lower reaction threshold.

A Review of the Respiratory Health Burden Attributable to Short-Term Exposure to Pollen

Respiratory diseases such as asthma, allergic rhinitis (AR) and chronic obstructive pulmonary disease (COPD) affect millions worldwide and pose a significant global public health burden. Over the years, changes in land use and climate have increased pollen quantity, allergenicity and duration of the pollen season, thus increasing its impact on respiratory disease. Many studies have investigated the associations between short-term ambient pollen (i.e., within days or weeks of exposure) and respiratory outcomes. Here, we reviewed the current evidence on the association between short-term outdoor pollen exposure and thunderstorm asthma (TA), asthma and COPD hospital presentations, general practice (GP) consultations, self-reported respiratory symptoms, lung function changes and their potential effect modifiers. The literature suggests strong evidence of an association between ambient pollen concentrations and almost all respiratory outcomes mentioned above, especially in people with pre-existing respiratory diseases. However, the evidence on sub-clinical lung function changes, COPD, and effect modifiers other than asthma, hay fever and pollen sensitisation are still scarce and requires further exploration. Better understanding of the implications of pollen on respiratory health can aid healthcare professionals to implement appropriate management strategies.

Thunderstorm asthma in seasonal allergic rhinitis: The TAISAR study

BACKGROUND

Asthma epidemics associated with thunderstorms have had catastrophic effects on individuals and emergency services. Seasonal allergic rhinitis (SAR) is present in the vast majority of people who develop thunderstorm asthma (TA), but there is little evidence regarding risk factors for TA among the SAR population.

OBJECTIVE

We sought to identify risk factors for a history of TA and hospital presentation in a cohort of individuals with SAR.

METHODS

This multicenter study recruited adults from Melbourne, Australia, with a past diagnosis of TA and/or self-reported SAR. Clinical information, spirometry results, white blood cell count, ryegrass pollen-specific (RGP-sp) IgE concentration, and fractional exhaled nitric oxide were measured to identify risk factors for a history of TA in individuals with SAR.

RESULTS

From a total of 228 individuals with SAR, 35% (80 of 228) reported SAR only (the I-SAR group), 37% (84 of 228) reported TA symptoms but had not attended hospital for treatment (the O-TA group), and 28% (64 of 228) had presented to the hospital for TA (the H-TA group). All patients in the H-TA group reported a previous asthma diagnosis. Logistic regression analysis of factors associated with O-TA and H-TA indicated that lower FEV1 value and an Asthma Control Questionnaire score higher than 1.5 were associated with H-TA. Higher blood RGP-sp IgE concentration, eosinophil counts, and fractional exhaled nitric oxide level were significantly associated with both O-TA and H-TA. Receiver operating curve analysis showed an RGP-sp IgE concentration higher than 10.1 kU/L and a prebronchodilator FEV1 value of 90% or lower to be biomarkers of increased H-TA risk.

CONCLUSION

Clinical tests can identify risk of a history of TA in individuals with SAR and thereby inform patient-specific treatment recommendations.

Children With Food Allergy Are at Risk of Lower Lung Function on High-Pollen Days

BACKGROUND

Grass pollen exposure is a risk factor for childhood asthma hospital attendances. However, its short-term influence on lung function, especially among those with other allergic conditions, has been less well-studied.

OBJECTIVE

To investigate this association in a population-based sample of children.

METHODS

Within the HealthNuts cohort, 641 children performed spirometry during the grass pollen season. Grass pollen concentration was considered on the day of testing (lag 0), up to 3 days before (lag 1-lag 3), and cumulatively (lag 0-3). We used linear regression to assess the relevant associations and examined potential interactions with current asthma, hay fever or eczema, and food allergy.

RESULTS

Associations were observed only in children with allergic disease (P value for interaction ≤ 0.1). In children with food allergy, grass pollen concentration was associated with a lower ratio of forced expiratory volume in 1 second to forced vital capacity (FEV₁/FVC) and lower mid-forced expiratory flows (FEF_25%-75%) at all lags (eg, at lag 2, FEV₁/FVC z-score = -0.50 [95% CI -0.80 to -0.20] and FEF_25%--75% z-score = -0.40 [-0.60 to -0.04] per 20 grains/m³ pollen increase), and increased bronchodilator responsiveness (BDR) at lag 2 and lag 3 (eg, at lag 2, BDR = (31 [95% CI -0.005 to 62] mL). In children with current asthma, increasing grass pollen concentration was associated with lower FEF_25%-75% and increased BDR, whereas children with current hay fever or eczema had increased BDR only.

CONCLUSIONS

A proactive approach needs to be enforced to manage susceptible children, especially those with food allergy, before high-grass pollen days.