Thunderstorm Asthma Risk Expected to Rise Due to Climate Change, Prevention and Early Warning Systems Crucial

Thunderstorm Asthma: A Growing Climate Change Challenge

Thunderstorm asthma, a severe form of asthma exacerbation, could become more frequent and unpredictable due to climate change, which is projected to increase aeroallergen prevalence and extreme weather events.

On November 21, 2016, Melbourne experienced the largest and deadliest recorded episode of thunderstorm asthma.

The Melbourne Event

On November 21, 2016, Melbourne experienced the largest and deadliest recorded episode of thunderstorm asthma. This event resulted in:

• 3,365 excess public hospital emergency department presentations for respiratory illnesses.
• 476 excess asthma-related hospital admissions.
• 10 associated fatalities.

Understanding Thunderstorm Asthma

Thunderstorm asthma refers to episodes of respiratory distress, bronchospasm, or asthma exacerbations linked to local thunderstorm activity. Outbreaks have been documented globally for over four decades.

Pathophysiology

Thunderstorm asthma results from a combination of three factors:

1. High concentration of aeroallergens: Such as pollen from temperate grasses (e.g., ryegrass).
2. An exposed and susceptible population: Individuals, often with allergic rhinitis or pre-existing asthma, are at risk.
3. Specific weather conditions: Thunderstorm winds and rain cause intact pollen grains to absorb moisture, swell, and burst, releasing hundreds of ultrafine, allergen-containing starch particles (less than 2.5 µm diameter). These small particles can be pushed to ground level and inhaled deep into the lungs, triggering severe asthma symptoms.

Regional triggers vary; ryegrass pollen is a primary trigger in Southeastern Australia, while weeds, olive pollen, and fungal spores are triggers globally. Events in Australia have consistently occurred during the spring season when grass pollen levels are high.

At-Risk Groups

Key risk factors include:

• Allergic rhinitis (hay fever): A major predictor, with prevalence ranging from 70% to 100% in thunderstorm asthma cohorts. Adults sensitive to grass pollen with seasonal hay fever are at highest risk.
• Pre-existing asthma and poor control: A prior asthma diagnosis predicts all severity levels. Poor asthma control, such as not regularly using a preventer or a recent asthma admission, significantly increases the odds of requiring hospitalization.
• Demographics and Ethnicity: Young adults and older children are most susceptible. The Melbourne event noted an increased risk among individuals of Asian and Indian descent, with six of the ten fatalities being from these groups.

Prediction and Biomarkers

Early warning systems use environmental modeling based on meteorological factors and pollen monitoring. Factors for forecasting high asthma admission days include thunderstorms, rainfall, specific wind directions, and high pollen counts over preceding days.

Biomarkers for high-risk individuals with seasonal allergic rhinitis include total eosinophil count, serum specific ryegrass IgE concentration, fractional exhaled nitric oxide (FeNO) level, and Asthma Control Questionnaire (ACQ) score. Lower lung function (FEV1) and specific IgE sensitivity to Lol p 5 are also strong candidate biomarkers.

Clinical Management and Prevention

Individual patient management focuses on preventative treatment and rapid intervention.

• Effective treatment of allergic rhinitis with intranasal steroid sprays and/or antihistamines.
• Adherence to an up-to-date asthma management plan, ensuring preventative and acute therapy availability during spring.
• Regular use of preventer medication, particularly inhaled corticosteroids, during high pollen seasons or predicted thunderstorms.
• Modern biologic agents and allergen immunotherapy show promise for high-risk individuals.

• Patients should use their asthma inhaler as prescribed for mild or moderate symptoms.
• Immediate emergency medical help is required for severe breathing problems or if reliever medication does not ease symptoms during or after a thunderstorm.

• Susceptible individuals are advised to take protective measures before, during, and after thunderstorms, including staying indoors, closing doors and windows, and setting air conditioners to recirculate air.

Future Risk

Climate change is expected to increase the frequency and distribution of severe thunderstorms and lengthen pollen seasons, leading to potentially more frequent and severe thunderstorm asthma events.

Climate change is expected to increase the frequency and distribution of severe thunderstorms and lengthen pollen seasons, leading to potentially more frequent and severe thunderstorm asthma events. This underscores the need for robust public health initiatives, early warning systems based on regular pollen and weather monitoring, and targeted preventive therapies.