Allergenic pollen calendar, prevalence of pollen allergy symptomatology and pollen sensitization in Alentejo region (South Portugal) are changing: Trends

Abstract

Introduction and objectives Pollen is one of the main sources of aeroallergens. Allergic rhinitis (AR), rhinoconjuntivitis (RC) and asthma (AA) are the main respiratory allergic diseases associated with aeroallergens exposure which prevalence tend to increase. Such chronic diseases and symptomatology have a significant negative impact on patient’s life quality with consequent economic impact, high health care system costs and loss of productivity due to the interference with the performance at work or at school. Usually it is frequent to associate seasonal symptoms to pollen sensitization, but for polysensitized patients, symptoms may persist several months or indefinite periods throughout the year. Évora is located in the Alentejo Region, in the inland of southern of Portugal. Évora has a continental temperate climate with warm and dry summers and mild wet winters, where droughts are frequent, and desertification seems to be in progress. The highest pollen counts of Portugal are recorded in Évora. The objectives of this study are to provide a regional pollen calendar, to analyse the sensitization to pollen aeroallergens of the atopic patients living in the Alentejo Region and to evaluate the trends. Material and Methods: Airborne pollen data from Évora monitoring station of the Portuguese Aerobiology Network – RPA (2001 to 2021), meteorological data of the Portuguese Institute of the Sea and Atmosphere, clinical data from children who attended the External Immunoallergology and Child Allergology Support Consultations (2015 to 2019) and from adult patients from External Consultation of Immunoallergology (2002 to 2007) at the Hospital do Espírito Santo of Évora were analysed. Patients were selected based on their clinical history and results from skin prick-tests (SPT). Patients with SPT positivity to pollens and with seasonal clinical symptoms were selected. The battery of the most representative inhalant pollen allergens from the geographic area was considered. Symptomatological surveys were completed by patients with pollinosis, and monthly and annual antihistaminic sales in Évora (2002 to 2007) were also used. Trends of pollen prevalence and sensitization were compared with results from previous studies. A pollen calendar of the Region was elaborated. Results: The most predominant airborne pollen types were: Quercus sp. 27%, Poaceae 20% and Olea 10%. Over these two decades, an increase of the Annual Pollen Integral for the most pollen types was obtained, which was statistically significant trends for Olea, Urticaceae and Asteraceae pollen types, and a decreasing statistically significant trend for Betulaceae, Amaranthaceae, Cupressaceae and Arecaceae pollen types. In the pediatric allergology clinic data, 27% of the children was pollen-sensitized. 72% presented AR, 38% Conjunctivitis, 34% AA, 25% AR and AA. 90% children were sensitized to grasses and 77% to Olea. Children monosensitized to Olea pollen were detected for the first time and an increase of Olea sensitization when it was compared with previous study occurred (previously Olea 36%). In the adult allergology clinic data, 24% of patients were sensitized to pollens. 51% had AR, 42% AR and AA and 7% AA. 99% were sensitized to grasses, 56% to Chenopodium, 47% to Olea. No patients monosensitized to Olea pollen or other pollen type were found, besides grasses. The highest frequency of pollinosis symptoms was recorded in May. A significant positive correlation between antihistaminic sales and the pollen counts (p <0.05) was observed. Conclusion: The pollen count showed a significant increase in the annual pollen integral, due to changes on the land use and/or to the influence of climate change. Grass pollen is the most important cause of pollinosis in this region, followed by Olea and Amaranthaceae pollens. They are also responsible for interannual variations in the antihistaminic sales during the spring. Over these two decades, changes in sensitization patterns of patients occurred, with a dramatic increase in Olea sensitization, particularly in children including monossensitization. Moreover, there are rising trends for increasing prevalence of more aggressive symptoms. The evolution in the data pollen, prevalence of pollinosis and symptoms must be monitored over time in order to detected changes in sensitization patterns and disease severity.