Risk Factors for Asthma Hospitalization among Adults and Elderly

Introduction

Air pollution, as a major and permanently rising hazard for the environment, is associated with large increases in medical expenses, morbidity and is estimated to cause about 800,000 annual premature deaths worldwide [11. Cohen AJ, Anderson HR, Ostro B, Pandey KD, Krzyzanowski M, et al. (2005) The global burden of disease due to outdoor air pollution. J Toxicol Env Health A 68: 1301-1307.]. The prevalence of allergic respiratory diseases has also increased during the last three decades, especially in industrialized countries [22. D'Amato G (2002) Environmental urban factors (air pollution and allergens) and the rising trends in allergic respiratory diseases. Allergy 57: 72: 30-33.-66. Allergic Rhinitis and its Impact on Asthma (ARIA) 2008 update (in collaboration with the World Health Organization, GA(2)LEN and AllerGen). Allergy 8-160.]. Furthermore, an examination of the historical record indicates that the prevalence of allergic rhinitis (AR) and allergic asthma have significantly increased over the past two centuries. Although the reasons for this increase are not fully elucidated, epidemiologic data suggest that certain pollutants produced from the burning of fossil fuels may have played an important role in the prevalence changes [77. Peterson B, Saxon A (1996) Global increases in allergic respiratory disease: The possible role of diesel exhaust particles. Ann Allerg Asthma Im 77: 263-270.,88. Saxon A, Diaz-Sanchez D (2005) Air pollution and allergy: you are what you breathe. Nat Immunol 6: 223-226.]. This increase may be partly explained by changes in environmental factors. Urbanization, the ever increasing automobile traffic with its high levels of vehicle emissions [77. Peterson B, Saxon A (1996) Global increases in allergic respiratory disease: The possible role of diesel exhaust particles. Ann Allerg Asthma Im 77: 263-270.,99. Krämer U, Koch T, Ranft U, Ring J, Behrendt H (2000) Traffic-related air pollution is associated with atopy in children living in urban areas. Epidemiology 11: 64-70.] and the changing lifestyle are linked to the rising frequency of respiratory allergic diseases [1010. D'Amato G, Liccardi G, D'Amato M, Holgate S (2005) Environmental risk factors and allergic bronchial asthma. Clin Exp Allergy 35: 1113-1124.]. Weather conditions can also affect both the biological and chemical air pollutants. There are evidences on the effect of air pollution upon allergens, increasing exposure to the latter, their concentration and/or biological allergenic activity [1111. Pénard-Morand C, Charpin D, Raherison C, Kopfersmitt C, Caillaud D, et al. (2005) Long-term exposure to background air pollution related to respiratory and allergic health in schoolchildren. Clin Exp Allergy 35: 1279-1287.-1313. Just J, Nikasinovic L, Laoudi Y, Grimfeld A (2007) Air pollution and asthma in children. Rev Fr Allergol 47: 207-213.]. Habitats and levels of pollen are changing in Europe, as a result of cultural factors, more international travel and climate change [1414. Vogl G, Smolik M, Stadler LM, Leitner M, Essl, F, et al. (2008) Modelling the spread of ragweed: Effects of habitat, climate change and diffusion. Eur Phys J-Spec Top 161: 167-173.-1717. Kiss L, Béres I (2006) anthropogenic factors behind the recent population expansion of common ragweed (Ambrosia artemisiifolia L.) in Eastern Europe: is there a correlation with political transitions? J Biogeogr 33: 2156-2157.]. There is now considerable evidence to suggest that climate change will have, and has already had, impacts on aeroallergens. These include impacts on pollen amount, pollen allergen city, pollen season, plant and pollen distribution, and other plant attributes [1818. Beggs PJ (2004) Impacts of climate change on aeroallergens: past and future. Clin Exp Allergy 34: 1507-1513.-2222. Kaminski U, Glod T (2011) Are there changes in Germany regarding the start of the pollen season, the season length and the pollen concentration of the most important allergenic pollens? Meteorol Z 20: 497-507.]. Hence, due to the continually increasing air pollution, respiratory diseases are of major concern worldwide.

Air pollution of Hungary is one of the highest in Europe. Around 16,000 annual premature deaths attributable to exposure to ambient PM₁₀ concentrations are estimated in the country [2323. Agren C (2010) Particles killing half a million. Acid News. AirClim. Air Pollution & Climate Secretariat, Sweden 2: 1-5.,2424. Barrett K, de Leeuw F, Fiala J, Larssen S, Sundvor I, et al. (2008) Health Impacts and Air pollution - An exploration of factors influencing estimates of air pollution impact upon the health of European citizens. ETC/ACC Technical Paper 13.]. Furthermore, airborne pollen levels are also high. The Carpathian basin, involving Hungary (Figure 1) is considered the most polluted region with airborne ragweed (Ambrosia) pollen in Europe. Ambrosia in Hungary discharges the most pollen of all taxa; the ratio of its pollen release compared to the total pollen release in the late summer period is around 60-71% [2525. Juhász M, Juhász IE (2002) A hazai gyomnövények aeropollinológiai jelent?sége. (Aeropollinological importance of domestic weeds.) Környezeti ártalmak és a légz?rendszer. (Environmental hazards and the respiratory system.)12: 149-160.]. Highest counts on peak days in Szeged, Southern Hungary, are about one order of magnitude higher than those in other cities of Europe [2626. Makra L, Juhász M, Béczi R, Borsos E (2005) The history and impacts of airborne Ambrosia (Asteraceae) pollen in Hungary. Grana 44: 57-64.]. The sensitivity of patients to ragweed in Szeged is 83.7% [2727. Kadocsa E, Juhász M (2000) A szénanáthás betegek allergénspektrumának változása a Dél-Alföldön (1990-1998). [Change of allergenic spectrum of hay-fever patients in Southern Great Plain (1990-1998).] Orvosi Hetilap 141: 12617-12620.]. About 30% of the Hungarian population has some type of allergy, 65% of them have pollen-sensitivity, and at least 60% of this pollen-sensitivity is caused by Ambrosia [2828. Járai-Komlódi M (1998) Ragweed in Hungary. In: Spieksma FThM, editor. Ragweed in Europe. Satellite Symposium Proceedings of 6th International Congress on Aerobiology. Perugia, Italy. Horsholm, Denmark: Alk-Abelló A/S 33-38.]. The number of patients with registered allergic illnesses has doubled and the number of cases of allergic asthma has become four times higher in Southern Hungary by the late 1990s over the last 40 years [2828. Járai-Komlódi M (1998) Ragweed in Hungary. In: Spieksma FThM, editor. Ragweed in Europe. Satellite Symposium Proceedings of 6th International Congress on Aerobiology. Perugia, Italy. Horsholm, Denmark: Alk-Abelló A/S 33-38.].