European Journal of Epidemiology

, Volume 27, Issue 4, pp 281–286

Analyzing atopic and non-atopic asthma

  • Juha Pekkanen
  • Jussi Lampi
  • Jon Genuneit
  • Anna-Liisa Hartikainen
  • Marjo-Riitta Järvelin
RESPIRATORY EPIDEMIOLOGY

DOI: 10.1007/s10654-012-9649-y

Cite this article as:
Pekkanen, J., Lampi, J., Genuneit, J. et al. Eur J Epidemiol (2012) 27: 281. doi:10.1007/s10654-012-9649-y

Abstract

There is a need to better define phenotypes of asthma. However, many studies have data available only on asthma and atopy, so they are often used to define ‘atopic’ and ‘non-atopic’ asthma. We discuss and illustrate the problems of analyzing such outcomes. We used the 31 year follow-up of the Northern Finland Birth Cohort 1966 (n = 5,429). ‘Atopic asthma’ and ‘non-atopic asthma’ were defined based on presence or absence of atopy (any skin prick test ≥3 mm) at age 31. Gender and ownership of cat in childhood were used as risk factors. Simple calculations on hypothetical datasets were used to support the conclusions. ‘Atopic asthma’ and ‘non-atopic asthma’, are not well separated disease entities. The association of a risk factor with ‘atopic asthma’ and ‘non-atopic asthma’ is determined both by its association with asthma and with atopy. E.g. if a risk factor is not associated with asthma, but is protective for atopy, this will produce a protective association with ‘atopic asthma’, but an opposite association with ‘non-atopic asthma’. This is the result from the typical analysis, which uses all non-asthmatics as the comparison group. Valid results, unconfounded by atopy, can be gained by comparing asthmatics to non-asthmatics separately among atopics and non-atopics, i.e. by doing the analysis stratified by atopy. If data only on asthma and atopy are available, asthma and atopy should be analyzed at first as separate outcomes. If atopic and non-atopic asthma are used as additional outcomes, valid results can be gained by stratifying the analysis by atopy.

Keywords

AsthmaAtopyEpidemiologyMethodsPhenotype

Supplementary material

10654_2012_9649_MOESM1_ESM.doc (61 kb)
Supplementary material 1 (DOC 61 kb)

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Juha Pekkanen
    • 1
    • 2
  • Jussi Lampi
    • 1
    • 2
  • Jon Genuneit
    • 3
  • Anna-Liisa Hartikainen
    • 4
  • Marjo-Riitta Järvelin
    • 5
    • 6
    • 7
  1. 1.Department of Environmental HealthNational Institute for Health and WelfareKuopioFinland
  2. 2.Public Health and Clinical NutritionUniversity of Eastern FinlandKuopioFinland
  3. 3.Institute of Epidemiology and Medical BiometryUlm UniversityUlmGermany
  4. 4.Department of Clinical Sciences/Obstetrics and GynecologyUniversity of OuluOuluFinland
  5. 5.Department of Biostatistics and EpidemiologySchool of Public Health, Imperial CollegeLondonUK
  6. 6.Child and Adolescent HealthNational Institute for Health and WelfareOuluFinland
  7. 7.Institute of Health Sciences and Biocenter OuluUniversity of OuluOuluFinland