Antibacterial use by birth year and birth season in children 0-2 years in Norway

Introduction: Consumption of antibacterials in children follows seasonal cycles, and time to first treatment depends on birth season. The aim of this study was to describe dispensing rate, one-year periodic prevalence, and age at first prescription in children aged 0-2 years in Norway.Methods: We used data from the Norwegian prescription database and included all dispensed prescriptions on systemic antibacterials in 2008-2017 during the first three years of life to children born 2005-2014. We calculated age by subtracting birth month and birth year from date of collection of prescription. We used multiple linear regression to investigate the effect of birth season on age at first dispensed prescription.Results: We included 714 262 prescriptions to 281 888 individuals (53.1% boys). In 2016, one-year-old boys had the highest periodic prevalence (35.6%) and the highest dispense rate (545/1000 individuals), followed by one-year-old girls (32.6%, 478/1000 individuals). The lowest prevalence and dispense rate in all age groups was found towards the end of the period. Winter months had the highest proportion of dispensed prescriptions, and children born in autumn were significantly younger when collecting their first prescription. On average, boys collected their first prescription 26 days younger compared to girls.Conclusion: One-year-olds have the highest periodic prevalence and the highest dispense rate. This contrast with results from other studies on Norwegian data and is probably attributed to our use of birth month for calculation of age. Children born in autumn were younger when collecting their first prescription compared to other birth seasons. It is unknown whether this has any long-term clinical implications.