Thunderstorm Asthma - An Unusual Phenomenon

Introduction

Thunderstorm asthma is a unique event with typical features of acute (short-term) asthma. It refers to increased bronchospasm (narrowing of airways) following thunderstorms in the surrounding areas. The phenomenon is rare and happens when specific populations and climatic factors coexist. Thunderstorm asthma can occur abruptly in spring or summer during stormy weather and gets exacerbated by grass pollen allergy. Affected patients present with cough, wheezing, and dyspnea (shortness of breath). These symptoms improve with bronchodilators (inhaled medicines for asthma). Still, severe thunderstorm asthma events can exhaust local medical services and result in deaths.

How Does Thunderstorm Asthma Occur?

The history of thunderstorm asthma dates back to the 1980s. It has only happened twenty times in the past thirty years worldwide. Historically, thunderstorm asthma events are poorly predicted, sporadic, and infrequent. Epidemic thunderstorm asthma (rapid spread of the disease within a given population) occurs when people are sensitized to triggering allergens in the air during a storm. The most predominant allergens are grass pollen and fungal spores. They can aid in thunderstorm asthma through the following mechanisms.

1. Pollens move into the cloud base by an upward current of warm air. In the cloud base, they break into finer particles due to electrical forces generated by the storm.

2. Pollens or fungal spores can absorb moisture leading to their swelling and rupture into smaller fragments.

3. These tiny particles are swept down to the ground by cool air and breezy wind. The susceptible population can inhale the allergens into the airways and lungs due to their smaller size.

After sensitization, the individual can experience bronchospasm within minutes. The acute response leads to IgE release (an antibody released in allergy) and mast cell (immune cell released in allergy) degranulation. As a result, it causes airway muscle contraction, mucosal swelling, and mucous production. An inflammatory response occurs due to the release of inflammatory mediators.

What Are the Clinical Features of Thunderstorm Asthma?

1. Patients with thunderstorm asthma have acute cough, dyspnea, wheezing, and breathing problems due to irritation, injury, inflammation, and obstruction.

2. Although bronchodilators are effective, hypoxia (low blood oxygen) and respiratory failure can occur.

3. Thunderstorm asthma affects groups of people close to each other at the storm front. Unexposed individuals who remain indoors are unaffected.

4. Prior asthma history is not an established feature. It is because 36 to 56 percent of people with thunderstorm asthma do not have an asthma diagnosis.

5. On a community level, a thunderstorm asthma event has a high demand for local health resources.

What Risk Factors Lead To Thunderstorm Asthma?

Several risk factors predispose individuals to thunderstorm asthma.

1. Individual Level:

• Allergic Rhinitis: Allergic rhinitis occurs in atopic (immune impairment that sensitizes to allergies) individuals and can occur with asthma. It is present in almost all thunderstorm asthma episodes. Studies reveal about 90 percent association of allergic rhinitis with thunderstorm asthma. Furthermore, the age distribution closely matches that of allergic rhinitis patients.

• Age: Patients affected by thunderstorm asthma are in the age range of 20 to 50 years. Studies report a variable incidence of thunderstorm asthma in children. Also, these studies report an under-diagnosis of the condition in children compared to non-thunderstorm asthma diagnoses.

• Gender and Ethnicity: Males are more affected than females by thunderstorm asthma. In a study reporting an epidemic, Asian or Indian ethnicity was a notable risk factor for the severity of thunderstorm asthma.

• Exposure to Outdoor Environment: People exposed to outdoor environments suffer more from thunderstorm asthma as compared to those who stay indoors.

2. Population Level: The risk factors for thunderstorm asthma at a population level include circulating triggering aeroallergens, coinciding storm activity, and a susceptible population. One must note that all the mentioned factors are required for the initiation of thunderstorm asthma events in a given population. The areas where these factors coexist experience a thunderstorm asthma epidemic. Air pollutants such as carbon monoxide, lead, particulate matter, and sulfur dioxide may also play a vital role in triggering the event.

What Are the Treatment and Preventive Strategies for Thunderstorm Asthma?

Management of thunderstorm asthma involves risk factor identification and preventive therapies. System-based approaches include forecast alert systems and climatic health literacy. Preventive strategies can reduce suffering and death related to severe and frequent thunderstorm asthma events. The following strategies focus on individual and population levels.

1. Individual Level:

• Asthmatic individuals are at higher risk of severe and life-threatening thunderstorm asthma. However, inhaled or oral corticosteroids (Dexamethasone and Prednisolone) can prevent severe attacks during storms. Therefore, appropriate asthma management with medical therapy is an important preventive strategy.

• Many patients have pollen sensitization and a history of allergic rhinitis. For these patients, education on thunderstorm asthma is useful. It is further helpful if coupled with emergency medication during an episode of thunderstorm asthma.

• The role of masks in reducing pollen inhalation and mitigating thunderstorm asthma severity needs exploring.

• Identification of patients with pollen sensitization is difficult. However, treating their pollen allergy with sublingual immunotherapy (SLIT) can decrease susceptibility to thunderstorm asthma. SLIT exposes the body to small amounts of allergens. The Food and Drug Administration (FDA) has approved allergy tablets and drops for thunderstorm asthma under the tongue. SLIT addresses various airborne allergens, such as pet dander, grass pollen, and fungal spores.

2. Population Level:

• Timely and targeted public health messages must be given in an evidence-based manner for maximal benefit. Local media is useful for the same. Messages should include information regarding event preparation and steps to take in a thunderstorm asthma outbreak. Further, people must keep asthma medication ready and remain indoors during emergencies.

• Predictive models can serve as warning systems. Community-level approaches are necessary to address the issue of uncontrolled asthma. It should be done along with the education of clinicians.

• Efforts to understand and modify the environmental risk factors are complex. Studies investigating the interaction between weather and pollen/spore dissemination may lead to better thunderstorm asthma warning systems.

• Individuals, organizations, and governments can contribute to climate change and air pollution that increase thunderstorm asthma exacerbations. Behavior modification at the community level can minimize these detrimental environmental effects. Further, it can improve lung health in citizens.

Conclusion

Thunderstorm asthma episodes are sporadic events occurring when sensitized individuals are exposed to allergens during a storm. These events result in severe asthma exacerbations and presentations. Patients, populations, and environments can be targeted to prevent an episode. Management can include public health strategies and individual advice. Early warnings related to meteorological factors can reduce the burden on affected individuals. Further studies into the complex interplay between climate, allergens, and individuals are needed to prepare for this unpredictable public health threat. Also, scientists must delve into understanding the mechanisms, biomarkers for risk classification, and improvements in targeted treatment approaches regarding the same.