Background of the APTA study

Asthma is globally the most common chronic disease in children (WHO 2011) and the prevalence of asthma in adult populations varies from 5 to 25%. Allergies are even more common with prevalence of 30-40%. The total cost of asthma in Europe is estimated at €17.7 billion per year, whereas the productivity loss due to poor asthma control is €9.8billion per year (ERS, White Book, 2003). Several studies (e.g. ISAAC, ECRHS) have reported substantial differences in the occurrence of asthma and allergies between European populations, including sharp differences between neighbouring regions (Hugg 2008). Both environmental exposures and genetic constitution play a role in the etiology of asthma (Gilmour 2006) and allergies, and in the recent years it has become apparent that there is a need to study further genetic constitution as a determinant of susceptibility to the adverse effects of environmental exposures (i.e. gene-environment interaction).

There is an increasing body of evidence that exposure to ambient air pollution during fetal period, early childhood, and later in life increases the risk of developing asthma. Exposure to pollen and other aeroallergens (molds, mites etc.) have been shown to increase symptoms and signs among asthmatics and other sensitized individuals. Our recent systematic review and meta-analysis showed that indoor dampness and molds increase the risk of asthma on average 50%, whereas the risk is as much as two-fold in infants and toddlers (Quansah 2012).

However, the role of pollen in the etiology of asthma is less well studied. It has been suggested that pollen and other aeroallergens (molds, mites etc.) increase the risk of asthma and allergies. Timing and duration of pollen season and distribution, as well as quality and quantity of pollens is expected to change due changing climate (e.g. Beggs 2010, Shea 2008). There is some evidence from experimental research that air pollution and pollen may have synergistic effects on asthma and allergic sensitization (Motta 2006, Namork 2006, Just 2002, Wyler 2000). Air pollutants, in particular ozone, PM, NO2 and SO2, can interact with plant derived allerganic paucimicronic particles and induce inflammatory effects on the airways by increasing permeability, easing penetration of allergens into the mucus membrane, and easing interaction with immune system cells (D’Amato 2011).

Climate change is the biggest global health threat of the 21st century and it will affect directly or indirectly all populations (Haines 2009, WHO 2009). Climate change will influence temperature, rainfall and the spatial distribution of vegetation, including several plant species with strong allergenic properties, and thus, these changes may have profound effects on asthma and allergies (e.g. Beggs 2004, Cecchi 2010). Climate change and the related changes in emissions and land use influence levels of air pollution; for example ozone levels are expected to increase as part of the climatic changes. For example, the northern parts of the world are expected to be subject to more intensive climatic changes than on average. The extreme meteorological conditions, such as heat waves and cold spells, have been predicted to increase in the future. Extreme air temperatures, increasing air pollution, and their synergy are suggested to be hazardous for health (e.g. Klein 2012).


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Last updated: 2.2.2015