Continued loss of asthma control following epidemic thunderstorm asthma

BACKGROUND: Epidemic thunderstorm asthma (ETSA) severely affected Melbourne, Australia in November 2016. There is scant literature on the natural history of individuals affected by ETSA. OBJECTIVE: A multicentre 12-month prospective observational study was conducted assessing symptomatology and behaviors of ETSA-affected individuals. METHODS: We used a structured phone questionnaire to assess asthma symptom frequency, inhaled preventer use, asthma action plan ownership and healthcare utilization over 12 months since the ETSA. Analysis of results included subgroup analyses of the “current,” “past,” “probable,“ and “no asthma” subgroups defined according to their original 2016 survey responses. RESULTS: Four hundred forty-two questionnaires were analyzed. Eighty percent of individuals reported ongoing asthma symptoms at follow-up, of which 28% were affected by asthma symptoms at least once a week. Risk of persistent asthma symptoms was significantly higher in those with prior asthma diagnosis, current asthma, and probable undiagnosed asthma (all p < 0.01). Of 442 respondents, 53% were prescribed inhaled preventers, of which 51% were adherent at least 5 days a week. Forty-two percent had a written asthma action plan and 16% had sought urgent medical attention for asthma in the preceding year. CONCLUSIONS: Following an episode of ETSA, patients experience a pivotal change in asthma trajectory with both loss of asthma control and persistence of de novo asthma. Suboptimal rates of inhaled preventer adherence and asthma action plan ownership may contribute to asthma exacerbation risk and susceptibility to future ETSA episodes. Longer-term follow-up is needed to determine the extent and severity of this apparent change.

Residential NO₂ exposure is associated with urgent healthcare use in a thunderstorm asthma cohort

BACKGROUND: There is increasing interest in the role of traffic-related air pollution (TRAP) in allergic airway diseases. Few studies investigate the relationship between TRAP exposure and acute exacerbations of asthma. OBJECTIVE: The 2016 Melbourne thunderstorm asthma epidemic provided an opportunity to investigate the relationship between proxies of TRAP exposure and asthma exacerbation requiring urgent healthcare in the previous 12 months. METHODS: Current asthmatics who presented to the 3 Emergency Departments of Melbourne's second-largest health service with epidemic thunderstorm asthma in November 2016 were identified and completed a standard questionnaire. Their residential addresses were geocoded and the annual average nitrogen dioxide (NO2) exposure for each patient was assigned using a validated satellite-based land use regression model. Residential distance to the nearest major road was calculated using ArcGIS. Multivariate logistic regression was used to investigate the relationship between each TRAP proxy and healthcare use, adjusting for potential confounders. RESULTS: From 263 thunderstorm asthma patients, 88 patients identified with current asthma were analysed. Those with higher mean annual residential NO2 exposure had greater odds of urgent healthcare use in the previous year (odds ratio [OR], 3.45 per one interquartile-range increase; 95% confidence interval [CI], 1.31–9.10; p = 0.01), however distance from major road (OR, 0.95 per 100-m increase; 95% CI, 0.80–1.13; p = 0.57) and living < 200 m from a major road (OR, 1.47; 95% CI, 0.29–7.45; p = 0.64) were not significantly associated. CONCLUSION: In current asthmatics who presented during an epidemic thunderstorm asthma event, greater exposure to residential NO2 was significantly associated with greater odds of asthma exacerbations requiring urgent healthcare in the previous 12 months.