Smoke from the 2019-20 ‘black summer’ bushfires triggered persistent symptoms in patients with severe asthma, even in those who took steps like staying indoors and closing windows and doors, a study shows.
Newcastle University researchers say the finding highlights the need to ensure patients are given specific advice on managing their asthma during bushfires, given that few used face masks or air purifiers and only a minority received advice from health professionals.
Based on survey responses from 240 patients severe refractory and eosinophilic asthma, the study also showed monoclonal antibody use for asthma was protective against persistent respiratory symptoms after the bushfires.
These were reported by approximately two thirds (65%) of participants, chiefly breathlessness (45%), cough (39%) and wheeze or whistling chest (39%).
Women, smokers and those with uncontrolled asthma before bushfire smoke exposure were most likely to experience persistent symptoms.
But level of smoke exposure was not associated with symptom intensity, the researchers said.
With an average 55 days of heavy bushfire smoke each, some 89% of participants said they avoided going outdoors, while 83% also said they avoided exercise as much as possible.
Writing in the International Journal of Environmental Research and Public Health, the team said the impact on patients with asthma had been intense.
“Most of the participants took action during the 2019/2020 bushfire period to mitigate the effects of smoke exposure, yet still experienced acute and persistent symptoms,” the authors said.
“While staying indoors and keeping the doors/windows shut may be effective in the short-term, the home will eventually equilibrate with the external environment during periods of prolonged exposure.”
They noted that although well-fitted P2/N95 masks and air purifiers were known to be effective in filtering particulate matter, uptake had been low during the fire season.
About two thirds of the participants were taking monoclonal antibody therapies (mepolizumab, omalizumab or benralizumab) for severe asthma. These patients had a 23% lower risk of persistent symptoms after exposure to high PM2.5 levels during the bushfire period (adjusted RR 0.77; 0.60–0.99; p = 0.046)
It was also noteworthy that less than half of participants (45%) with severe asthma obtained advice regarding bushfire smoke exposure minimisation or managing their asthma during fires.
Of those who did get advice, two-thirds received it from their GP, 25% from a respiratory/asthma specialist and 37% acted on information in news/current affairs stories.
“Health care professionals should ensure that people with severe asthma are aware of the risks of exposure, effective mitigation strategies and adequately prepared to manage their asthma during bushfires,” the researchers said.