Allergic rhinitis.

<p>Meta-analyses of the adjusted odds of <b>allergic rhinitis</b> (sensitized to at least 1 aero-allergen; secondary endpoint) in early school age and pet ownership in the first 2 years of life for: A), cat only vs. no pets; B), dog only vs. no pets; C) cat and dog only vs. no pets; D) bird only vs. no pets; E) rodents only vs. no pets.</p

Prevalence of current asthma, allergic asthma (sensitized to ≥1 aero-allergen), allergic rhinitis (sensitized to ≥1 aero-allergen) and allergic sensitization (≥1 aero-allergen >0.35 kU/L) at last follow-up assessment between 6 to 10 years in 11 European birth cohorts.

<p>n.a. = not assessed.</p>1<p>in DARC, AMICS-Barcelona and AMICS-Menorca, sensitization data were only available for the age of 4 years.</p

Allergic asthma.

<p>Meta-analyses of the adjusted odds of <b>allergic asthma</b> (sensitized to at least 1 aero-allergen; secondary endpoint) in early school age and ownership of pets in the first 2 years of life for: A), cat only vs. no pets; B), dog only vs. no pets; C) cat and dog only vs. no pets; D) bird only vs. no pets; E) rodents only vs. no pets.</p

Birth cohort acronym, study setting, year of recruitment, number of children recruited, and pet ownership during the first 2 years of life in 11 European birth cohorts (sorted from north to south).

<p>ECA: Environment and Childhood Asthma Study. BAMSE: Children, Allergy, Milieu, Stockholm, Epidemiological Survey. DARC: Danish Allergy Research Council Study. PIAMA-NHS: The Prevention and Incidence of Asthma and Mite Allergy – Natural History Study. MAS: Multi-center Allergy Study. LISA: Lifestyle-related Factors on the Immune System and Development of Allergies in Childhood Study. GINI-B: German Infant Nutritional Intervention Study (observational part). AMICS: Asthma Multicentre Infant Cohort Study.</p>1<p>and no other furry or feathered pet.</p>2<p>3754 initially recruited and followed-up until 2 years; for ECA: 1877 invited for longer follow-up.</p>3<p>More children are part of the Leicester 1998 cohort, but for the present meta-analyses on early pet ownership we included only children who were recruited during the 1^st year of life.</p

Current asthma.

<p>Meta-analyses of the adjusted odds ratios of <b>asthma</b> at 6–10 years of age and pet ownership in the first 2 years of life for: A), cat only vs. no pets; B), dog only vs. no pets; C) cat and dog only vs. no pets; D) bird only vs. no pets; E) rodents only vs. no pets.</p

Allergic sensitization.

<p>Meta-analyses of the adjusted odds of <b>allergic sensitization</b> (sensitized to at least 1 aero-allergen) in early school age and pet ownership in the first 2 years of life for: A), cat only vs. no pets; B), dog only vs. no pets; C) cat and dog only vs. no pets; D) bird only vs. no pets; E) rodents only vs. no pets. (There were no IgE data available for Leicester 1998 cohort.)</p

Integrating clinical and epidemiological data on allergic diseases across birth cohorts: A harmonization study in the mechanisms of the development of allergy project

International collaborations among birth cohorts to better understand asthma and allergies have increased in the last years. However, differences in definitions and methods preclude direct pooling of original individual participant data. We harmonized data from 14 birth cohorts, with three to 20 follow-ups, from nine European countries, as part of the Mechanisms of the Development of Asthma and Allergies (MeDALL) project. The harmonization process followed six steps: organization of the harmonization panel; identification of variables relevant to MeDALL objectives (candidate variables); proposal of a definition for each candidate variable (reference definition); assessment of the compatibility of each cohort variable to its reference definition (inferential equivalence) and classifications of this inferential equivalence as complete, partial, or impossible; workshop to agree on the reference definitions and classifications of inferential equivalence; and data preparation and delivery through a knowledge management portal. We agreed on 137 reference definitions. The inferential equivalence of 3,551 cohort variables to their corresponding reference definition was classified as complete, partial and impossible for 70%, 15% and 15% of the variables, respectively. A harmonized database was delivered. In birth cohorts of asthma and allergies, the harmonization of data for pooled analyses is feasible and may achieve high inferential comparability. The MeDALL harmonization approach can be used in other collaborative projects