Incidence and determinants of antibiotic use by age two: a prospective cohort study
- 1University of Michigan
Abstract
BackgroundHalf 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.
ObjectivesWe assessed risk factors for time to first antibiotic use between birth to age 2 to identify modifiable drivers of antibiotic use.
MethodsWe analyzed interviews from mothers of 1032 children participating in the mother-child Center for Oral Health Research in Appalachia cohort 2 between 2011--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.
ResultsBy 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.
ConclusionsEarlier 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.
SynopsisO_ST_ABSStudy QuestionC_ST_ABSWhat modifiable risk factors predict antibiotic use prior to age 2?
Whats Already Known on This SubjectEarly childhood antibiotic use is common and influenced by clinical diagnoses like ear and respiratory infections. Socioeconomic factors shape prescribing patterns, but the contribution of early-life behaviors, including timing of solid food introduction, remains poorly understood.
What This Study AddsThis study identifies early solid food introduction as an independent predictor of earlier antibiotic use and quantifies the strong temporal links between childhood illnesses and initial antibiotic exposure, highlighting modifiable factors that may reduce unnecessary early antibiotic use.
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BibTeX
@misc{staal2026incidence,
title = {{Incidence and determinants of antibiotic use by age two: a prospective cohort study}},
author = {A. Staal and H. Zhen and T. Zhang and M. C. Byrd and N. Kamdar and J. R. Shaffer and D. W. McNeil and M. Marazita and B. Foxman},
howpublished = {medRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.23.26363799},
url = {https://www.medrxiv.org/content/10.64898/2026.09.23.26363799v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Incidence and determinants of antibiotic use by age two: a prospective cohort study
AU - A. Staal
AU - H. Zhen
AU - T. Zhang
AU - M. C. Byrd
AU - N. Kamdar
AU - J. R. Shaffer
AU - D. W. McNeil
AU - M. Marazita
AU - B. Foxman
PY - 2026
DA - 2026/09/23
PB - medRxiv
DO - 10.64898/2026.09.23.26363799
UR - https://www.medrxiv.org/content/10.64898/2026.09.23.26363799v1
AB - BackgroundHalf 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. ObjectivesWe assessed risk factors for time to first antibiotic use between birth to age 2 to identify modifiable drivers of antibiotic use. MethodsWe analyzed interviews from mothers of 1032 children participating in the mother-child Center for Oral Health Research in Appalachia cohort 2 between 2011--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. ResultsBy 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. ConclusionsEarlier 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. SynopsisO_ST_ABSStudy QuestionC_ST_ABSWhat modifiable risk factors predict antibiotic use prior to age 2? Whats Already Known on This SubjectEarly childhood antibiotic use is common and influenced by clinical diagnoses like ear and respiratory infections. Socioeconomic factors shape prescribing patterns, but the contribution of early-life behaviors, including timing of solid food introduction, remains poorly understood. What This Study AddsThis study identifies early solid food introduction as an independent predictor of earlier antibiotic use and quantifies the strong temporal links between childhood illnesses and initial antibiotic exposure, highlighting modifiable factors that may reduce unnecessary early antibiotic use.
ER -