Farm environment during infancy and incidence of allergic diseases between the age of 31 and 46 years – results from a prospective birth cohort study from Finland

<b>Background:</b> Living in a farm during early life seems to protect from development of allergic diseases during childhood. However, it remains unclear if the farm environment during early life protects from development of allergic diseases also during adulthood. <b>Methods:</b> In Northern Finland Birth Cohort study subjects born in the northern Finland in 1966 were followed up at the age of 46. Current analyses are based on subjects with information about doctor diagnosed asthma (N=6684) and allergic rhinitis (N=6182) at the age of 46. Prenatal exposure to the farm environment was documented before or at birth. Information on health and sosioeconomic status was collected at the age of 31 and 46 and information on current farm environment at the age of 46. <b>Results:</b> Being born to a family having farm animals decreased the risk of doctor-diagnosed (DD) asthma ever at the age of 46 (adjusted odds ratio [aOR] 0.80, 95% confidence interval [CI] 0.66-0.97), DD allergic rhinitis ever at the age of 46 (aOR 0.72 95% CI 0.62-0.84) and the development of new DD allergic rhinitis between the age of 31 and 46 years (aOR 0.78 95% CI 0.61-1.00). Number of animal species in farm and home environment during early childhood was inversely and dose-dependently associated with the risk of development of new allergic rhinitis between the age of 31 and 46 years. Farm environment during infancy had no effect on the development of new asthma between the age of 31 and 46. <b>Conclusions:</b> This prospective birth cohort study shows, that farm environment during early life may protect from allergic rhinitis, but not from asthma, throughout the life.