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Living at high altitude and risk of hospitalisation for atopic asthma in children: results from a large prospective birth-cohort study
  1. U Kiechl-Kohlendorfer1,
  2. E Horak2,
  3. W Mueller3,
  4. R Strobl4,
  5. C Haberland5,
  6. FM Fink6,
  7. M Schwaiger6,
  8. KH Gutenberger7,
  9. H Reich7,
  10. D Meraner2,
  11. S Kiechl8
  1. 1Department of Paediatrics, Division of Neonatology, Innsbruck Medical University, Innsbruck, Austria
  2. 2Department of Paediatrics, Division of Paediatric Cardiology and Pulmonology, Innsbruck Medical University, Innsbruck, Austria
  3. 3Department of Paediatrics, Reutte County Hospital, Reutte, Austria
  4. 4Department of Paediatrics, Lienz County Hospital, Lienz, Austria
  5. 5Department of Paediatrics, Kufstein County Hospital, Kufstein, Austria
  6. 6Department of Paediatrics, St Johann County Hospital, St Johann, Austria
  7. 7Department of Paediatrics, St Vincent’s Hospital Zams, Zams, Austria
  8. 8Department of Neurology, Innsbruck Medical University, Innsbruck, Austria
  1. Correspondence to:
    Prof U Kiechl-Kohlendorfer
    Department of Paediatrics, Division of Neonatology, Innsbruck Medical University, Anichstrasse 35 6020 Innsbruck, Austria; ursula.kohlendorfer{at}i-med.ac.at

Abstract

Background: Asthma is among the most common chronic diseases in childhood and is steadily increasing in prevalence. Better characterisation of factors that determine the risk of hospitalisation for atopic asthma in childhood may help design prevention programmes and improve our understanding of disease pathobiology. This study will focus on the altitude of residence.

Methods: This is an ongoing prospective birth-cohort study that enrolled all live-born infants in the Tyrol. Between 1994 and 1999, baseline data were collected for 33 808 infants. From 2000 to 2005, all children hospitalised for atopic asthma at the age of ⩾6 years (n = 305) were identified by a careful search of hospital databases. Disease status was ascertained from the typical medical history, a thorough examination and proof of atopy.

Results: Living at higher altitude was associated with an enhanced risk of hospitalisation for atopic asthma (multivariate RRs (95% confidence interval 2.08 (1.45 to 2.98) and 1.49 (1.05 to 2.11) for a comparison between altitude categories ⩾1200 m and 900–1199 m versus <900 m; p<0.001). This finding applied equally to hospital admissions in spring, summer, autumn and winter. When altitude of residence was analysed as a continuous variable, the risk for asthma hospitalisation increased by 7% for each 100-m increase in altitude (p = 0.013).

Conclusions: This large prospective study shows a significant association between the risk of hospitalisation for atopic asthma and altitude of residence between 450 and 1800 m. The underlying mechanisms remain to be elucidated, but it is tempting to speculate about a role for altitude characteristics such as the decline in outdoor temperature and air humidity and increase in ozone levels, which may trigger airway hyper-responsiveness and attenuate lung function.

  • ICD-9, International Classification of Disease-Ninth Revision
  • ICD-10, International Classification of Disease, Tenth Revision

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