Trends in allergic sensitization and exposure to olive pollen in Alentejo

Abstract

Background: Olive pollen is among the most allergenic species in theMediterranean and the second cause of pollen allergy. The grow-ing increase in the cultivation of olive groves as well as its use asan ornamental plant in Alentejo may have an impact on exposureto allergens, potentially increasing the risk of allergic sensitization.This study aimed to comprehensively characterize the prevalenceand trends of allergic sensitization in Alentejo, Portugal, in relation to the pollen levels over the last decade. Method: A retrospective analysis (2006–2021) of the population sensitization data found at Clinidata®XXI at HESE was performed; the levels and type of specific IgE for the different allergen groups,with a special focus on olive tree pollen were collected. The pollen levels were collected from https://lince.di.uevora.pt/polen/index.jsp, University of Évora. Analysis of the association between the two variables was performed. Results: The extension of cultivar groves increased over the last decade in Alentejo, having almost tripled around the Alqueva basin(from ~20,000 ha to >70,000 ha). The annual pollen index varied between 1441 and 10,403 pollen/m 3 , the highest being 2021 season. The annual pollen index presents a tendency to increase in the lastyear. Interestingly a tendency to diminish between 2011 (~10,500pollen/m 3 ) and 2018 (~4000 pollen/m 3 ) while it tended to increase between 2018 and 2021 (>15,000 pollen/m 3 ), not following thesteady increase profile of olive cultivar groves. Among the sensitized population, aged 1 to 96 years, 35.5% corresponded to the 4–12 age group. The highest prevalence was found in the 13–20 age group (47.4%). The IgE levels were also higher in the groups 4–12 and 13–20 years old. The prevalence of positive olive sIgE also followed a biphasic pattern, reaching a nadir in2017–2018, the years with the lower levels of olive pollen, followed by an increase between 2019 and 2021. The highest mean levels of sIgE were registered in 2013, 2018 and 2019 and the lowest in2014 and 2020 seasons. When the mean levels of sIgE is considered, a 5-fold and a 2-fold increase were observed in 2021 compared to2018 and to 2011, respectively, in keeping with the high pollen lev-els. When taken together, the profile of sIgE followed the profile of pollen index with the annual pollen index, evidencing an association between these variables. Conclusion: In conclusion, these results suggest that the exposure to highest concentration of olive pollen favours the increase of sensitization of the population, particularly children. Other data should be analysed to validate the observations in this case study.