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Multi-decade changes in pollen season onset, duration, and intensity: A concern for public health?

ABSTRACT: Longitudinal shifts in pollen onset, duration, and intensity are public health concerns for the growing number of individuals with pollen sensitization. National analyses of long-term pollen changes are influenced by how a plant's main pollen season (MPS) is defined. Prior Swiss studies have inconsistently applied MPS definitions, leading to heterogeneous conclusions regarding the magnitude, directionality, and significance of multi-decade pollen trends. We examined national pollen data in Switzerland between 1990 and 2020, applying six MPS definitions (2 percentage-based and 4 threshold-based) to twelve relevant allergenic plants. We analyzed changes in pollen season using both linear regression and locally estimated scatterplot smoothing (LOESS). For 4 of the 12 plant species, there is unanimity between definitions regarding earlier onset of pollen season (p < 0.05), with magnitude of 31-year change dependent on specific MPS definition (hazel: 9-18 days; oak: 5-13 days; grasses: 8-25 days; and nettle/hemp: 6-25 days). There is also consensus (p < 0.05) for modified MPS duration among hazel (21-104% longer), nettle/hemp (8-52% longer), and ash (18-38% shorter). Between-definition agreement is highest for MPS intensity analysis, with consensus for significant increases in seasonal pollen quantity (p < 0.05) among hazel, birch, oak, beech, and nettle/hemp. The largest relative intensification is noted for hazel (110-146%) and beech (162-237%). LOESS analysis indicates that these multi-decade pollen changes are typically nonlinear. The robustness of MPS definitions is highly dependent on annual pollen accumulation, with definition choice particularly influential for long-term analysis of low-pollen plants such as ragweed. We identify systematic differences between MPS definitions and suggest future aerobiologic studies apply multiple definitions to minimize bias. In summary, national pollen onset, duration, and intensity have shifted for some plants in Switzerland, with MPS definition choice affecting magnitude and significance of these variations. Future public health research can determine whether these temporal and quantitative pollen changes correlate with longitudinal differences in population pollen sensitization.

SUBMITTER: Glick S

PROVIDER: S-EPMC8182784 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:AimTo investigate whether birch pollen allergy symptoms are linked with gut microbiota changes and whether probiotics have an effect on these.MethodsForty seven children with confirmed birch pollen allergy were randomized to receive either a probiotic combination of Lactobacillus acidophilus (L. acidophilus) NCFM (ATCC 700396) and Bifidobacterium lactis (B. lactis) Bl-04 (ATCC SD5219) or placebo in a double-blind manner for 4 mo, starting prior to onset of the birch pollen season. Symptoms were recorded in a diary. Blood samples were taken for analysis of cytokines and eosinophils. Fecal samples were analysed for microbiota components, calprotectin and IgA. Nasal swabs were taken for analysis of eosinophils.ResultsThe pollen season induced a reduction in Bifidobacterium, Clostridium and Bacteroides which could not be prevented by the probiotic intervention. During the intervention, significantly higher numbers of B. lactis 11.2 x 10(7) +/- 4.2 x 10(7) vs 0.1 x 10(7) +/- 0.1 x 10(7) bacteria/g feces (P < 0.0001) and L. acidophilus NCFM 3.5 x 10(6) +/- 1.3 x 10(6) vs 0.2 x 10(6) +/- 0.1 x 10(6) bacteria/g feces (P < 0.0001) were observed in the probiotic group compared to the placebo group. During May, there was a tendency for fewer subjects, (76.2% vs 95.2%, P = 0.078) to report runny nose, while during June, fewer subjects, 11.1% vs 33.3%, reported nasal blocking in the probiotics group (P = 0.101). Concomitantly, fewer subjects in the probiotic group had infiltration of eosinophils in the nasal mucosa compared to the placebo group, 57.1% vs 95% (P = 0.013). Eye symptoms tended to be slightly more frequent in the probiotic group, 12.5 d [interquartile range (IQR) 6-18] vs 7.5 d (IQR 0-11.5) (P = 0.066) during May. Fecal IgA was increased in the placebo group during the pollen season; this increase was prevented by the probiotics (P = 0.028).ConclusionBirch pollen allergy was shown to be associated with changes in fecal microbiota composition. The specific combination of probiotics used was shown to prevent the pollen-induced infiltration of eosinophils into the nasal mucosa, and indicated a trend for reduced nasal symptoms.

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Multi-decade changes in pollen season onset, duration, and intensity: A concern for public health?

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