Respiratory tract infections (RTIs) are most common in under-school-aged children, and they have a range of effects on society. In this study we aimed to examine modifiable risk factors relating to the young child’s immediate environments, namely the home, daycare, and free-time activities. 

This is a prospective birth cohort study carried out in Southwest Finland. We followed 1570 children for RTIs from birth until the age of 3 years, and documented medical-, psychological-, environmental-, and social factors applying diaries and questionnaires. A subset of 982 children were included in a more intensive infection follow-up, which included nasal swabs for virus analysis and visits at the study clinic during acute RTIs. 

We found maternal depressive symptoms during pregnancy to predict higher cumulative rates of acute otitis media by the age of 10 months in the infant, and maternal emotional loneliness to predict higher cumulative rates of physician visits within the same age frame. Acute otitis media, physician visits, and antibiotic consumption were marginally less frequent for infants of families with social loneliness in either or both parents. 

Comparing monthly sick days (days with symptoms of a RTI), antibiotic medications, and parental absences from work for children 0-24 months of age, we detected a steep rise of these measures after the start of daycare, and a subsequent clear decline within our follow-up, which ended 9 months after the initiation of daycare. When comparing the same outcome measures at the ages of 30-35 months of age, there were no significant differences for sick days between children in home care and those in out-of-home daycare. However, antibiotic medications were significantly more common for children in daycare centres, as compared to those in home care. When examining possible links between infant swimming activities and respiratory symptoms for children up to 17 months of age, no significant differences with respect to rates of RTIs could be observed. There was a statistically significant association between swimming and rhinovirusassociated wheeze for children with atopic eczema. 

This study strengthens our understanding on modifiable risk factors for RTIs in young children and is of relevance with respect to preventative strategies.