ACAAI: Acute Asthma Spikes in Autumn Don't Correspond to Allergen Prevalence

PHILADELPHIA, Nov. 15 -- Children with asthma are more likely to have exacerbations requiring admission to the pediatric ICU in the late summer and early fall months, reported investigators here.

In a retrospective review of records of children admitted to a pediatric ICU for asthma exacerbations over a nine-year period, 41% of all admissions occurred during August, September, and October, reported Pulin Patel, D.O., of the Children's Hospital of Michigan/Detroit Medical Center, and colleagues.

But those exacerbations don't appear to correlate with the airborne concentrations of allergens prevalent at that time of year, suggesting that other factors may also be involved in triggering asthma exacerbations, the investigators wrote in a poster presented at the American College of Allergy, Asthma & Immunology meeting.

About 4% of the 1,500 children with asthma who are admitted to their hospital annually have life-threatening exacerbation requiring admission to the pediatric ICU, and these admissions peak in the late summer and early fall months, they noted.

One theory for the spike in PICU admissions is that the children could be reacting to aeroallergens that are prevalent at that time of year, particularly Alternaria, or ragweed.

To test this theory they conducted a retrospective chart review of all patients admitted to the PICU for asthma exacerbation from 1997 to 2005, and divided admissions into four three-month groups: August-October, November-January, February-April, and May-July.

They reviewed records for sensitivity to 11 aeroallergens: trees, grasses, weeds, ragweed, outdoor molds, Alternaria, indoor molds, cat, dog, roach and dust mites. They compared sensitivities to the admissions during the four time groups.

They found that, as they had previously observed, there was a higher prevalence of admissions to the PICU for asthma exacerbations during August, September and October, consisting of 216 of 529 admissions (41%). These admissions occurred during the period when Alternaria and ragweed exposures are highest.

But when they looked at the records of the 81 children for whom one-year skin prick test results were available, they found that sensitivity to tree pollen was significantly higher among the August-October group compared with the November-January group-84% versus 46%, (P=0.022).

Compared with the February-April group, children with exacerbations from August to October had significantly greater sensitivity to tree pollen (84% vs. 43%, P=0.037), weed pollen (67% vs. 25%, P=0.049), and dust mites (47% vs. 9%, P=0.033).

They also found that among the children with November to January exacerbations, dust mite sensitivity was significantly higher than among kids with February to April exacerbations (57% vs. 9%, P=0.033). Dust mite sensitivity was also higher among those children requiring PICU admission from May through July compared with those hospitalized from February through April (53% vs. 9%, P=0.041).

"The increased rate of pediatric ICU admissions did not correlate with the aeroallergen sensitivity to the prevalent allergen during August, September and October," the investigators wrote. "Therefore we suspect other factors, such as viral upper respiratory infections, weather changes, and medication noncompliance; in addition to aeroallergen sensitivity that predisposes severe asthma exacerbation during the late summer and early fall months."

An allergist who was not involved in the study said that the phenomenon may be caused by what he calls the "cesspool of life."

"School starts, all these kids start swapping viral infections, and we do see that in September and October, in terms of [increased] hospital visits, ER visits, and in this case, pediatric ICU visits," said Todd Mahr, M.D., director of pediatric allergy and clinical immunology at Gundersen Lutheran Medical Center in Madison, Wis.