Grass pollen exposure associated with higher pediatric asthma readmission rates
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Children and adolescents with asthma experienced statistically significant higher hospital readmission rates during grass pollen season compared with the rest of the year, according to a study published in Pediatric Allergy and Immunology.
Preventive therapies before grass pollen season could reduce readmissions, Mehak Batra, PhD, MPH, MDS, teaching fellow in the department of public health at La Trobe University School of Psychology and Public Health in Melbourne, Australia, and colleagues wrote.
The researchers examined data from the Victorian Admitted Episodes Dataset on 47,456 children and adolescents (age range, 2-18 years; 60.2% male) admitted to the hospital for asthma. They also collected weather data from the Bureau of Metrology and the Environment Protection Authority Victoria between 1997 and 2009.
Within 28 days of discharge, 2,152 (4.53%) of these patients were readmitted to the hospital for asthma for a mean readmission rate of 0.49 (standard deviation [SD], 0.72).
Patients aged 2 to 5 years had a higher mean daily readmissions rate at 0.26 (SD, 0.52) than those aged 6 to 12 years (0.14; SD, 0.38) and aged 13 to 18 years (0.07; SD, 0.28). Also, boys had a higher mean daily readmission rate (0.27; SD, 0.54) than girls (0.21; SD, 0.46).
Mean daily readmissions also were above the overall mean during peak pollen season, defined as October through December, when daily grass pollen concentrations ranged between 0 grains/m3 and 356 grains/m3.
Mean daily readmission rates were 1.44 times (95% CI, 1.03-2.02) higher during grass pollen season compared with outside of pollen season.
Patients aged 2 to 5 years had the highest readmission rates during grass pollen season, with an incidence rate ratio (IRR) of 1.99 (95% CI, 1.26-3.14), followed by patients aged 6 to 12 years (IRR = 1.47; 95% CI, 0.78-2.79) and those aged 13 to 18 years (IRR = 0.6; 95% CI, 0.29-1.23).
Further, the researchers found significant nonlinear associations between lag 2 daily pollen concentrations and all daily readmissions (P = .03), as well as those among children aged 2 to 5 years (P = .02) and aged 6 to 12 years (P < .001), and among boys (P = .01).
For lag 0, researchers only observed a weak association between mean daily readmission rates and grass pollen above 128 grains/m3.
Additionally, patients aged 6 to 12 years experienced a significant association between cumulative pollen values over 4 days and daily readmissions, the researchers found.
Based on these findings, the researchers called for interventions that target children with severe or under-controlled asthma before the pollen season begins. These patients also should receive communications and interventions when they are discharged from the hospital, which may reduce hospital readmissions and improve both treatment adherence and patient satisfaction.
Monitoring daily readmission counts and following up with children at higher risk for readmission, along with stronger links between the health system and community including asthma education, may prevent hospitalizations and readmissions as well, the researchers wrote.
Perspective
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The link between grass pollen counts and pediatric hospital readmission is significant but not surprising. This study is epidemiologic in nature, drawing on an impressive database of climate, pollen and hospital data in Australia. It is not a clinical study but serves to remind us that pollen may act as irritant, allergen and enhancer of particulate exposure injury to pediatric lung health.
We are aware of thunderclap asthma as a complication of grass pollen allergy. This study reminds us as asthma specialists to look at air quality and grass pollen in context of asthma exacerbation prevention and treatment.
Whether results would be similar elsewhere in the world, however, is difficult to answer given climate trends and regional differences across the globe. I cannot extrapolate here intelligently, but I believe there is a grain of truth to this study’s findings for global pediatric lung health.
Awareness of grass pollen as a “kindling” agent and asthma trigger in the patient with asthma is important. Optimizing asthma medications seasonally to prevent asthma inpatient stays or readmissions is key.
Conducting a longitudinal clinical study of children with confirmed grass pollen allergy and asthma in the context of hospital admissions and readmissions in Australia would add practicality and possibly change guidelines.
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