by Karin C. Lødrup Carlsen, Stephanie Roll, Kai-Håkon Carlsen, Petter Mowinckel, Alet H. Wijga, Bert Brunekreef, Maties Torrent, Graham Roberts, S. Hasan Arshad, Inger Kull, Ursula Krämer, Andrea von Berg, Esben Eller, Arne Høst, Claudia Kuehni, Ben Spycher, Jordi Sunyer, Chih-Mei Chen, Andreas Reich, Anna Asarnoj, Carmen Puig, Olf Herbarth, Jestinah M. Mahachie John, Kristel Van Steen, Stefan N. Willich, Ulrich Wahn, Susanne Lau, Thomas Keil, GA 2 LEN WP 1.5 ‘Birth Cohorts’ working group
To examine the associations between pet keeping in early childhood and asthma and allergies in children aged 6–10 years. Design
Pooled analysis of individual participant data of 11 prospective European birth cohorts that recruited a total of over 22,000 children in the 1990s. Exposure definition
Ownership of only cats, dogs, birds, rodents, or cats/dogs combined during the first 2 years of life. Outcome definition
Current asthma (primary outcome), allergic asthma, allergic rhinitis and allergic sensitization during 6–10 years of age. Data synthesis
Three-step approach: (i) Common definition of outcome and exposure variables across cohorts; (ii) calculation of adjusted effect estimates for each cohort; (iii) pooling of effect estimates by using random effects meta-analysis models. Results
We found no association between furry and feathered pet keeping early in life and asthma in school age. For example, the odds ratio for asthma comparing cat ownership with “no pets” (10 studies, 11489 participants) was 1.00 (95% confidence interval 0.78 to 1.28) (I2?=?9%; p?=?0.36). The odds ratio for asthma comparing dog ownership with “no pets” (9 studies, 11433 participants) was 0.77 (0.58 to 1.03) (I2?=?0%, p?=?0.89). Owning both cat(s) and dog(s) compared to “no pets” resulted in an odds ratio of 1.04 (0.59 to 1.84) (I2?=?33%, p?=?0.18). Similarly, for allergic asthma and for allergic rhinitis we did not find associations regarding any type of pet ownership early in life. However, we found some evidence for an association between ownership of furry pets during the first 2 years of life and reduced likelihood of becoming sensitized to aero-allergens. Conclusions
Pet ownership in early life did not appear to either increase or reduce the risk of asthma or allergic rhinitis symptoms in children aged 6–10. Advice from health care practitioners to avoid or to specifically acquire pets for primary prevention of asthma or allergic rhinitis in children should not be given.