{
  "abstract": "Background: Suboptimal serum 25-hydroxyvitamin D [25(OH)D] status remains prevalent among pediatric populations, yet serial data on age-specific patterns and seasonal evolution in young children are limited.\n\nObjective: To characterize age-stratified serum 25(OH)D status, seasonal patterns, sex-specific trends, and temporal changes in serum 25-hydroxyvitamin D [25(OH)D] among children aged 0–10 years.\n\nMethods: This repeated cross-sectional study included 6,816 children undergoing well-child visits in Ningbo, China (2018–2025); a different sample of children was assessed in each calendar year. Serum 25(OH)D was measured by LC-MS/MS and categorized as deficient (< 20 ng/mL), 20–30 ng/mL, or sufficient (> 30 ng/mL). Multivariable linear regression (for 25(OH)D concentrations) and multivariable logistic regression (for 25(OH)D deficiency, < 20 ng/mL), together with stratified analyses (by season, sex, age group, and pandemic period), were performed.\n\nResults: Overall, 38.1% of children had suboptimal serum 25(OH)D (< 30 ng/mL), including 9.4% with 25(OH)D deficiency (< 20 ng/mL). Sufficiency (> 30 ng/mL) declined markedly with age: 72.0% (< 1 year), 50.4% (1–3 years), 36.8% (3–6 years), and 8.6% (6–10 years). Seasonally, sufficiency was highest in autumn (71.7%) and lowest in spring (55.2%), with 25(OH)D < 30 ng/mL peaking in spring (44.8%). No significant sex differences were observed. Mean serum 25(OH)D concentrations showed a gradual upward trend from 2018 to 2025 in all seasons—an observed trend in this serially sampled cross-sectional sample; however, older children remained predominantly below 30 ng/mL, and the age-related gap widened over time.\n\nConclusions: Despite temporal improvements, suboptimal serum 25(OH)D status (< 30 ng/mL) remains common, with a pronounced age-dependent decline and persistent spring vulnerability; because only 93 children were aged 6–10 years, conclusions for school-aged children remain provisional. Age-targeted prevention strategies extending beyond early childhood warrant evaluation in intervention studies.\n\nClinical trial number: Not applicable.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 4,
  "authors": [
    {
      "name": "Jiaxing Yi"
    },
    {
      "name": "Qiao Wang"
    },
    {
      "name": "Yue Bi"
    },
    {
      "name": "Wenyuan Liu",
      "orcid": "0000-0001-9681-0507"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/0s2xgk1wszhrp.bib",
  "cited_by": 0,
  "doi": "10.1186/s12889-026-30115-3",
  "fulltext_url": null,
  "id": "0s2xgk1wszhrp",
  "issns": [
    "1471-2458"
  ],
  "landing_url": "https://link.springer.com/article/10.1186/s12889-026-30115-3",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2734|Vitamin D Research Studies"
    ]
  ],
  "openalex": "W7223710427",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": "Springer Science and Business Media LLC",
  "ris": "https://research.draconitic.com/paper/0s2xgk1wszhrp.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:54Z",
      "native_id": "10.1186/s12889-026-30115-3",
      "source": "crossref",
      "url": "https://link.springer.com/article/10.1186/s12889-026-30115-3"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "issn:1471-2458",
      "subfield": "epidemiology-public-health"
    }
  ],
  "title": "Serum 25-hydroxyvitamin D status in Ningbo children: age and seasonal determinants from an eight-year retrospective cross-sectional analysis",
  "title_text": "Serum 25-hydroxyvitamin D status in Ningbo children: age and seasonal determinants from an eight-year retrospective cross-sectional analysis",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:19:54Z",
  "url": "https://research.draconitic.com/paper/0s2xgk1wszhrp",
  "venue": "BMC Public Health",
  "versions": []
}