title: Epidemiology of asthma exacerbations and their relation with environmental factors in the Basque Country.
abstract: BACKGROUND
  Asthma is a highly prevalent chronic inflammatory disease characterised by reversible airflow obstruction and hyperreactivity and inflammation of the airways. Factors that cause and/or trigger asthma attacks include host-related factors (genetic predisposition, obesity and sex) and environmental factors (allergens, infections, occupational sensitisation, smoking status, pollution and diet).
  
  
  OBJECTIVE
  To describe the epidemiology of asthma exacerbations (AEs) in the Basque Country and to explore its relationship with potentially associated environmental variables. We studied a total of 31,579 emergency department (ED) visits and 28,189 hospitalisations due to asthma. We describe the trends, incidence, seasonality and the influence of age and sex, as well as of exposure to NO2 , CO, PM, O3 , and pollen, temperature, relative humidity and flu status. We calculated the Pearson's R correlation coefficient for the study variables.
  
  
  RESULTS
  The incidence was 486 and 88.9 cases per 100,000 people for ED visits and hospitalisations, respectively. Slightly over half (53.5%) of the ED cases were male, while females represented 62.6% of the hospital admissions. Hospitalisations are tending to decrease in children and increase in over 64-year-olds. Peaks in cases occur at the beginning of autumn in children and in winter in adults. AEs were correlated positively with exposure to NO2 , CO and to the influenza virus and negatively with temperature and exposure to O3 . These relationships vary, however, with age and season.
  
  
  CONCLUSIONS
  Rates of hospitalisation for AEs and trends in these rates over time are different in adults and children with the patterns varying by sex, season and environmental conditions.
authors.affiliation: Public Health Division of Gipuzkoa, Department of Health of the Regional Government of the Basque Country, Donostia, Spain.|CIBER of Epidemiology and Public Health, Madrid, Spain.|Biodonostia Research Institute, Donostia, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Altzibar
authors.affiliation: Public Health Division of Gipuzkoa, Department of Health of the Regional Government of the Basque Country, Donostia, Spain.|CIBER of Epidemiology and Public Health, Madrid, Spain.|Biodonostia Research Institute, Donostia, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Tamayo-Uria
authors.affiliation: Public Health Division of Bizkaia, Department of Health of the Regional Government of the Basque Country, Bilbo, Spain.
authors.forename: V
authors.initials: V
authors.lastname: De Castro
authors.affiliation: Laboratory of Public Health, Regional Government of the Basque Country, Bilbo, Spain.
authors.forename: X
authors.initials: X
authors.lastname: Aginagalde
authors.affiliation: Environmental Management, Regional Government of the Basque Country, Bilbo, Spain.
authors.forename: M V
authors.initials: MV
authors.lastname: Albizu
authors.affiliation: Biodonostia Research Institute, Donostia, Spain.|Department of Preventive Medicine and Public Health, University of the Basque Country UPV/EHU, Leioa, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Lertxundi
authors.affiliation: Paediatric Emergency Department, Cruces University Hospital, Basque Health Service, Bilbo, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Benito
authors.affiliation: Emergency Department, Donostia University Hospital, Basque Health Service, Donostia, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Busca
authors.affiliation: Allergology Department, Basurto University Hospital, Basque Health Service, Bilbo, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Antepara
authors.affiliation: Department of Paediatrics, Donostia University Hospital, Basque Health Service, Donostia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Landa
authors.affiliation: Public Health Division of Alava, Department of Health of the Regional Government of the Basque Country, Vitoria-Gasteiz, Spain.
authors.forename: O
authors.initials: O
authors.lastname: Mokoroa
authors.affiliation: Public Health Division of Gipuzkoa, Department of Health of the Regional Government of the Basque Country, Donostia, Spain.|CIBER of Epidemiology and Public Health, Madrid, Spain.|Biodonostia Research Institute, Donostia, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Dorronsoro
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000393:Air Pollutants; D000397:Air Pollution; D000485:Allergens; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D004777:Environment; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008875:Middle Aged; D011058:Pollen; D012621:Seasons; D013030:Spain / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D000485:Allergens
keywords: air pollutants; asthma exacerbation; emergency department; hospitalisation; influenza; pollen; weather