From:  An expert position paper on environment, occupation and climate change effects on allergic respiratory diseases in Italy

 Effects of pollen on allergic and respiratory health from meta-analysis of systematic reviews.

StudyPopulation/AreaExposureOutcomeStudy design includedEffect estimationChange of effect (if available)
Erbas et al., 2018 [153]Australia, Canada, USA, Spain, Israel (0–18 years).
14 studies (3 included in meta-analysis)
GraminaceaeEmergency room visits for asthma and wheezingTime series, case-crossover, descriptive studies+ 1.88% (95% CI 0.94–2.82) with a 3-day lag per 10 pollen grains per m3Major effects in the 5–17 age group
Annesi-Maesano et al., 2023 [154]Predominantly high-income countries (all age groups).
73 studies (2–4 studies in meta-analysis)
GraminaceaeSevere asthma exacerbationsTime series, case-crossover, cohort, cross-sectional+ 2%; (95% CI 1–3) in all ages for increment from 0 to 50 granules/m3. Borderline effect in childrenGreater effects in children, no effect in the elderly
Shrestha et al., 2021 [155]United Kingdom, Australia, USA, Canada, Mexico, Sweden, Belgium (0–18 years).
12 studies (2–3 in meta-analysis)
Graminaceae, BetulaAsthma hospitalizationsTime series, case-crossover, cohortChange (%) = + 0.85% (CI −3.24; 4.95) per increment of 10 granules/m3 of Graminaceae;
Change (%) = + 0.85% (CI 0.40, 1.30) for Betula
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Kitinoja et al., 2020 [156]France, Switzerland, USA, Spain, Finland, Austria, Germany, Denmark, United Kingdom, Australia (all age groups).
26 studies (16 in meta-analysis)
Total and taxa-specific pollenSelf-reported symptoms of asthma and allergy and lung functionPanel studiesAt least one symptom of asthma or allergy: + 2% (CI 1–3%); lower respiratory symptoms: + 0.8% (CI 0–1.5%);
upper respiratory symptoms: + 6.6% (CI 4.4–8.7%);
ocular symptoms: + 10.9% (CI 5–17.2%) for a total pollen increase of 10 granules/m3. No significant effect on lung function
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CI: confidence interval.