Short-term exposure to grass pollens is associated with airway inflammation in 1-2 days and airway obstruction in 2-3 days in people at risk of atopy due to their family history.
A study of 936 participants in the Melbourne Atopy Cohort compared the result of their clinical tests at the 18-year follow-up visit with environmental pollen data from the day of and three days prior to their testing.
Almost a third of participants had current asthma (30%), 13% reported current hay fever and 47% were sensitised to at least one grass pollen.
The study period covered three grass pollen seasons from September to February in 2009 to 2011. Although a minor thunderstorm asthma event occurred during the study period, none of the participants attended the clinic on or around this time.
The study, published in Allergy, found there were significant positive associations between grass pollen exposure and FeNO as a measure of airway inflammation at days 1 and 2.
As well there were significant inverse associations between grass pollen exposure and FEF25-75% and FEV1/FVC ratio at days 2 and 3.
Exposure to higher levels of grass pollen appeared to increase airway inflammation and airway obstruction in participants with current asthma compared to those with no asthma and in adults, but not in children or adolescents.
The study, from the Allergy and Lung Health Unit in the University of Melbourne’s Centre for Epidemiology and Biostatistics led by Professor Shyamali Dharmage, found adults and individuals with hay fever and pollen sensitisation may also be at higher risk.
“These findings are fundamental to inform individual and public health preventive strategies for asthma exacerbation and hospital admissions due to grass pollen exposure, such as a preventive asthma therapy or allergen immunotherapy,” the study authors said.
“In addition, the use of modern technologies such as early warning systems on smartphones and social media sites for impending high pollen days, as well as broader information technology systems (ITS)-based public education to the adverse effects of grass pollen exposure could increasingly play an important preventive role.”
First author and PhD candidate in the Allergy and Lung Health Unit Sabrina Idrose told the limbic the most surprising finding was probably the temporal effects.
“We saw that with airway inflammation it was 1-2 days after grass pollen exposure but with airway obstruction it was 2-3 days after grass pollen exposure. So that was an interesting finding.”
“In our study we thought the more delayed effect was probably because it was [exposure to] whole pollen grains rather than in thunderstorm asthma events with [exposure to] ruptured pollen grains which can penetrate into the lower airways.”
“During a thunderstorm asthma event we hypothesise that the grass pollen grains rupture into very tiny particles and that’s why the effects may be faster.”
She noted that other studies had not observed similar changes in lung function but that was mainly because they measured FEV1 alone.
“We didn’t see changes in the forced expiratory volume but we did see changes mainly in the mid-forced expiratory flow.”
“And we speculate that the reason we did not see an association with FEV1 was that maybe because the changes were most prominent in the middle to small airways rather than the more distal airways.”