NEW YORK (Reuters Health) - People who say their asthma gets worse when the weather changes are on to something, new research hints.
Dr. Alan Baptist of the University of Michigan School of Medicine in Ann Arbor and his colleagues found that pediatric emergency department visits for asthma attacks jumped after increases -- or decreases -- in humidity, while rises in temperature also sent more asthmatic kids to the ER.
“When we ask patients what set off your asthma...they’ll say it was the change in the weather,” Baptist noted in an interview with Reuters Health. And while the National Institutes of Health lists weather changes as a risk factor for worsening of asthma symptoms, he and his colleagues note in their report, no one has yet investigated whether this is true, independent of known asthma aggravators like pollution and airborne allergens.
This led Baptist and his team to look at all pediatric emergency department visits to the Children’s Hospital of Michigan in Detroit for treatment of asthma flare ups over a two-year period, including 25,401 visits in all. There were 35 such visits, on average, every day.
The researchers looked at day-to-day and within-day changes in temperature and humidity, controlling for levels of several air pollutants and for counts of seasonal allergens like pollen and mold.
They found that for every 10 percent decrease in relative humidity from one day to the next, there were about 1.3 additional visits for asthma attacks two days later. And for every 10 percent increase in humidity within a single day, there were 1.1 more visits two days later. On the day following a temperature jump, there were 1.8 additional visits for every 10-degree Fahrenheit increase.
“The timing and magnitude of change in humidity, rather than the direction, may be a more important influence on asthma exacerbations,” the researchers write in the Annals of Allergy, Asthma and Immunology.
It’s not clear why changes in humidity and temperature might lead to asthma exacerbations, Baptist said, although these shifts may aggravate the inflammation in the airways of the lungs that is a hallmark of asthma.
No matter what the mechanism involved, he added, people with asthma should pay particularly close attention to their symptoms if they notice changes in temperature and humidity, and use their peak flow monitor, if they have one, to check their lung function regularly.
“Catching asthma early can prevent the attack from worsening and can at times prevent a trip to the emergency department,” Baptist said.
SOURCE: Annals of Allergy, Asthma and Immunology, September 2009.
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