Extreme Heat Events may Influence Hay Fever Rates in Adults According to Recent Study in The Journal of Allergy and Clinical Immunology: In Practice

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Increasing temperatures create longer pollen season and increased pollen production.

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Our study is the first one to provide empirical evidence of how such increases in extreme heat events contribute to allergic diseases such as hay fever at a national level.

Hay fever, or seasonal allergic rhinitis, affects 17.6 million adults in the United States and results in $11.2 billion in related medical expenses. In a study published on November 8 in The Journal of Allergy and Clinical Immunology: In Practice, investigators from the University of Maryland School of Public Health concluded an increased prevalence of hay fever among adults in the United States is associated with the frequency of extreme heat events.

In the study “Exposure to extreme heat events is associated with increased hay fever prevalence among nationally representative sample of US adults: 1997-2013”, researchers linked the National Health Interview Survey Data with extreme heat event data. The researchers identified extreme heat events between 1997 and 2013 at the county level by comparing daily maximum temperatures to temperatures based on 30 years of baseline data (1960-1989). They found that adults in the highest quartile of exposure to extreme heat events were 7% more likely to suffer from hay fever compared to those in the lowest quartile of exposure.

“It is well established that extreme heat events are on the rise and this trend is projected to continue in response to changing climate,” said Amir Sapkota, PhD, senior author of the manuscript. “Our study is the first one to provide empirical evidence of how such increases in extreme heat events contribute to allergic diseases such as hay fever at a national level.”

Researchers found the timing of extreme heat events also made a difference in hay fever rates. There was a clear association between extreme heat events that occurred during spring season and more pronounced rates of hay fever. The same association was not observed in the fall season.

“While the exact mechanisms by which long-term exposures to extreme heat events increase the risk of hay fever remain unclear, one potential explanation is changes in plant phenology,” said Crystal R. Upperman, PhD, lead author of the manuscript. “Higher frequency of extreme heat events, particularly in the winter and spring, may lead to longer pollen seasons as warmer temperatures contribute to earlier onset of greening and flowering of plants including trees that are major sources of pollen.”

While the researchers do acknowledge the 7% increase in prevalence of hay fever as modest, they argue it could have significant implications for millions of people in the United States including decreased quality of life and more medical expenses.

The American Academy of Allergy, Asthma & Immunology (AAAAI) represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic and immunologic diseases. Established in 1943, the AAAAI has more than 6,900 members in the United States, Canada and 72 other countries. The AAAAI’s Find an Allergist/Immunologist service is a trusted resource to help you find a specialist close to home.

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