Incidence and determinants of antibiotic use by age two: a prospective cohort study

Background: Half of US children are prescribed an antibiotic by age 2. Maternal education and socio-economic factors influence prescribing but the role of other factors, such as age of solid food introduction is unknown. Objectives: We assessed risk factors for time to first antibiotic use between birth to age 2 to identify modifiable drivers of antibiotic use. Methods: We analyzed interviews from mothers of 1032 children participating in the mother-child Center for Oral Health Research in Appalachia cohort 2 between 2011 and 2017. The cohort enrolled healthy, English-speaking, pregnant White women > 18 years with singleton pregnancies. We used time-to-event analyses and a Cox Proportional Hazards model to describe and estimate hazard ratios (HRs) for time to first antibiotic. Results: By age 2, 78% of children received at least one antibiotic (median age at first antibiotic: 12.5 months). Over half (58%) of antibiotics prescribed were for ear infections. After adjustment for household income and birth quarter as fixed variables, time of solid food introduction (aHR: 4.75; 95% CI: 3.19, 7.07), time of first ear infection (aHR: 3.28; 95% CI: 2.58,4.17), and time of first illness (aHR: 4.60; 95% CI: 3.32,6.36) were significantly associated with time of first antibiotic use. Conclusions: Earlier time of solid food introduction was associated with earlier antibiotic use. Childhood illnesses, especially ear infections, also strongly influence antibiotic initiation. These modifiable factors offer targets to reduce unnecessary early antibiotic use.