{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T21:20:06Z","timestamp":1792790406889,"version":"4.5.0"},"posted":{"date-parts":[[2026,9,29]]},"group-title":"Epidemiology","reference-count":42,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T00:00:00Z","timestamp":1790640000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"name":"National Institute of Dental and Craniofacial Research at the National Institutes of Health","award":["R01-DE014899"],"award-info":[{"award-number":["R01-DE014899"]}],"id":[{"id":"https:\/\/ror.org\/004a2wv92","id-type":"ROR","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,9,29]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>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.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Objectives<\/jats:title>\n                  <jats:p>We assessed risk factors for time to first antibiotic use between birth to age 2 to identify modifiable drivers of antibiotic use.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>We analyzed interviews from mothers\u2019 of 1032 children participating in the mother-child Center for Oral Health Research in Appalachia cohort 2 between 2011\u20142017. The cohort enrolled healthy, English-speaking, pregnant White women \u226518 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.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>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\u20137.07), time of first ear infection (aHR: 3.28; 95% CI: 2.58\u20134.17), and time of first illness (aHR: 4.60; 95% CI: 3.32\u20136.36) were significantly associated with time of first antibiotic use.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>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.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Synopsis<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Study Question<\/jats:title>\n                    <jats:p>What modifiable risk factors predict antibiotic use prior to age 2?<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>What\u2019s Already Known on This Subject<\/jats:title>\n                    <jats:p>Early 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.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>What This Study Adds<\/jats:title>\n                    <jats:p>This 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.<\/jats:p>\n                  <\/jats:sec>\n                <\/jats:sec>","DOI":"10.64898\/2026.09.23.26363799","type":"posted-content","created":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T00:20:16Z","timestamp":1790727616000},"source":"Crossref","is-referenced-by-count":0,"title":["Incidence and determinants of antibiotic use by age two: a prospective cohort study"],"prefix":"10.64898","author":[{"given":"Adrianna","family":"Staal","sequence":"first","affiliation":[{"name":"Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Harry","family":"Zhen","sequence":"additional","affiliation":[{"name":"Department of Infection Prevention & Epidemiology, University of Michigan Health,Ann Arbor, MI"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Toni","family":"Zhang","sequence":"additional","affiliation":[{"name":"Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor, MI"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Morgan C.","family":"Byrd","sequence":"additional","affiliation":[{"name":"Department of Head and Neck Surgery & Communication Sciences, Duke University School of Medicine, Durham, N.C"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1898-1594","authenticated-orcid":false,"given":"Neil","family":"Kamdar","sequence":"additional","affiliation":[{"name":"Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor, MI"},{"name":"Sheps Center for Health Services Research, University of North Carolina, Chapel Hill, NC, United States"},{"name":"Center for Population Health Sciences, Stanford University, Stanford, CA, United States"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1897-1131","authenticated-orcid":false,"given":"John R.","family":"Shaffer","sequence":"additional","affiliation":[{"name":"Department of Oral and Craniofacial Sciences, School of Dental Medicine; Department of Human Genetics, School of Public Health, University of Pittsburgh, Pittsburgh, PA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0766-8455","authenticated-orcid":false,"given":"Daniel W.","family":"McNeil","sequence":"additional","affiliation":[{"name":"Department of Community Dentistry and Behavioral Science, College of Dentistry, University of Florida, Gainesville, FL USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2648-2832","authenticated-orcid":false,"given":"Mary L.","family":"Marazita","sequence":"additional","affiliation":[{"name":"Department of Oral and Craniofacial Sciences, School of Dental Medicine; Department of Human Genetics, School of Public Health; Center for Craniofacial and Dental Genetics, Department of Oral and Craniofacial Sciences, School of Dental Medicine; Clinical and Translational Science Institute, University of Pittsburgh, Pittsburgh, PA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6682-238X","authenticated-orcid":false,"given":"Betsy","family":"Foxman","sequence":"additional","affiliation":[{"name":"Center for Molecular and Clinical Epidemiology of Infectious Diseases, Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026100317101511000_2026.09.23.26363799v1.1","doi-asserted-by":"publisher","DOI":"10.1001\/jama.2016.4151"},{"key":"2026100317101511000_2026.09.23.26363799v1.2","doi-asserted-by":"publisher","DOI":"10.1093\/cid\/civ076"},{"key":"2026100317101511000_2026.09.23.26363799v1.3","doi-asserted-by":"publisher","DOI":"10.1016\/j.mayocp.2020.07.019"},{"key":"2026100317101511000_2026.09.23.26363799v1.4","doi-asserted-by":"publisher","DOI":"10.1038\/s41366-021-01023-w"},{"key":"2026100317101511000_2026.09.23.26363799v1.5","doi-asserted-by":"publisher","DOI":"10.3390\/antibiotics12071092"},{"key":"2026100317101511000_2026.09.23.26363799v1.6","unstructured":"National Institute on Deafness and Other Communication Disorders. 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