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

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