{
  "abstract": "Objective\n\nHbA1c reflects glucose exposure over the preceding 8-12 weeks. We characterised the lagged seasonal association between monthly climatological temperature normals and HbA1c in a 12-year hospital cohort and examined whether a similar pattern was present in patient-level records.Research design and methods\n\nWe analysed 633,838 HbA1c measurements (387,678 patients; 633,737 with complete covariates) from a Chinese tertiary hospital (2014-2025). Cross-correlation was assessed for lags of 0-6 months using monthly HbA1c means and fixed monthly climatological temperature normals. Patient-level distributed-lag regression with cluster-robust standard errors and generalised estimating equations was used as a complementary analysis.Results\n\nHbA1c was inversely correlated with the climatological temperature series most strongly at a 2-month lag (r = -0.297, P < 0.001) rather than concurrently (r = -0.127, P = 0.14). Pooled by calendar month, the lag-2 seasonal association was strong (r = -0.977, R² = 0.955), with a seasonal HbA1c amplitude of 0.235% (2.6 mmol/mol; peak March, trough September), strongest under age 60 and attenuated during COVID-19. Patient-level regression showed a similar lag pattern, with the largest coefficient at lag 2 (β = -0.0088% per °C; 95% CI -0.0093 to -0.0082; P < 0.001), and the individual-level partial R² was 0.15%.Conclusions\n\nThe study identified a reproducible seasonal HbA1c pattern that aligned most strongly with the 2-month-shifted climatological temperature series, with significant correspondence also at 1 and 3 months. Because the exposure was a fixed calendar-month normal, the findings should be interpreted as a lagged seasonal association rather than evidence of a causal temperature effect or a specific 2-month biological delay. The small individual-level partial R² (0.15%) also argues against applying the population amplitude directly to individual treatment decisions. Future research should evaluate whether seasonal contextualisation can optimise laboratory monitoring and re-testing strategies near diagnostic thresholds.",
  "abstract_shown": true,
  "affiliations": [
    "Laboratory Department of Ruian People's Hospital, Zhejiang, Wenzhou, China."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Kecheng Li"
    },
    {
      "affs": [
        0
      ],
      "name": "Fei Xia"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/d2555724hyf4t.bib",
  "cited_by": 0,
  "doi": "10.3389/fendo.2026.1990386",
  "fulltext_url": "https://europepmc.org/articles/PMC13683058",
  "id": "d2555724hyf4t",
  "issns": [
    "1664-2392"
  ],
  "landing_url": "https://europepmc.org/article/MED/42908711",
  "language": "eng",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2307|Climate Change and Health Impacts"
    ]
  ],
  "openalex": "W7220842808",
  "pdf_url": "https://europepmc.org/articles/PMC13683058?pdf=render",
  "pmcid": "PMC13683058",
  "pmid": "42908711",
  "published": "2026-10-07",
  "publisher": "Frontiers Media SA",
  "ris": "https://research.draconitic.com/paper/d2555724hyf4t.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:53Z",
      "native_id": "MED:42908711",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42908711"
    },
    {
      "first_seen": "2026-10-30T12:20:20Z",
      "native_id": "10.3389/fendo.2026.1990386",
      "source": "crossref",
      "url": "https://www.frontiersin.org/articles/10.3389/fendo.2026.1990386/full"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:2307|Climate Change and Health Impacts",
      "subfield": "pharmacology-toxicology"
    }
  ],
  "title": "Calendar month seasonality of HbA1c and its phase relationship with climatological temperature in 633,838 clinical measurements.",
  "title_text": "Calendar month seasonality of HbA1c and its phase relationship with climatological temperature in 633,838 clinical measurements.",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:20:20Z",
  "url": "https://research.draconitic.com/paper/d2555724hyf4t",
  "venue": "Frontiers in endocrinology",
  "versions": []
}