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Farm environment during pregnancy and childhood and polysensitization at the age of 31 - Prospective birth cohort study in Finland

Karvonen AM1*, Lampi J1*, Keski-Nisula L2,3, Auvinen J4,5, Toppila-Salmi S6,7, Järvelin MR4,8,9,10, Pekkanen J1,11

1Environmental Health Unit, Department of Health Security, Finnish Institute for Health and Welfare, Kuopio, Finland
2Department of Obstetrics and Gynecology, Kuopio University Hospital, Kuopio, Finland
3Department of Health Sciences, Clinical Medicine, University of Eastern Finland, Kuopio, Finland
4Center for Life Course Health Research, Faculty of Medicine, University of Oulu, Finland
5Oulunkaari Health Center, Ii, Finland
6Haartman Institute, University of Helsinki, Helsinki, Finland
7Skin and Allergy Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
8Department of Epidemiology and Biostatistics, MRC–PHE Centre for Environment & Health, School of Public Health, Imperial College London, UK
9Unit of Primary Care, Oulu University Hospital, Finland
10Biocenter Oulu, University of Oulu, Finland
11Department of Public Health, University of Helsinki, Helsinki, Finland
*These authors contributed equally to this work.

J Investig Allergol Clin Immunol 2021; Vol. 31(1)
doi: 10.18176/jiaci.0455

Background: Farm environment, especially contact with farm animals in early childhood may prevent from allergic sensitization during adulthood. However, prospective associations between exposure to farm environment and polysensitizationhave not been studied. Polysensitization is a risk factor for asthma and asthma morbidity.
Objective: To investigate whether farming environment in the early childhood, especially animal exposure, is associated with sensitization to specific allergens and polysensitization at the age of 31.
Methods: In a prospective birth cohort study, 5509 subjects born in northern Finland in 1966 were skin prick testedat the age of 31against birch, timothy, cat and house dust mite. Prenatal exposure to the farming environment was documented at birth, whereas information on childhood exposure to pets was only collected retrospectively at the age of 31. Logistic regression was used in the statistical analyses.
Results: Being born to a family with farm animalswas associated with the reducedrisk of sensitization against birch, timothy or cat(adjusted odds ratio,aOR=0.55[95% confidence interval 0.43-0.70];aOR=0.62[0.48-0.79];aOR=0.60[0.47-0.75]) and polysensitization at the age of 31 (aOR=0.62[0.48-0.80]). Sensitization against birch, timothy and cat as well as polysensitization was dose-dependently and inversely associated with number of animal species present during childhood. No association was found with sensitization against house dust mite.
Conclusions: Growing up on a farm and contact with the higher numbers of animal species in childhood is associated with less sensitization against birch, timothy and
cat allergensand polysensitization in adulthood, but not with sensitization against house dust mite.

Key words: Atopy, Sensitization, Farm environment, Adults, Polysensitization, Monosensitization.