Background: Circadian Syndrome (CircS) encompasses cardiometabolic risk factors and comorbidities, indicating an elevated susceptibility to cardiovascular disease and type 2 diabetes. Methods: This cross-sectional study aimed to investigate the association between vitamin D levels and each of the following: CircS, metabolic syndrome (MetS), and the individual components of CircS. Data from 14,907 adults who participated in the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2018 were utilized. CircS was defined based on MetS components, alongside depression, short sleep, and non-alcoholic fatty liver disease (NAFLD). Results: Our results indicated that low vitamin D levels exhibited meaningful associations with CircS, with vitamin D deficiency and inadequacy demonstrating 2.21-fold (95% CI 1.78–2.74, p < 0.001) and 1.33-fold (95% CI 1.14–1.54, p < 0.001) increases in CircS odds, respectively. The association between vitamin D deficiency and CircS was stronger than that with MetS. Additionally, a dose-response gradient in odds of CircS components, particularly with short sleep duration, was noted as serum vitamin D levels decreased. Conclusions: our findings highlight a significant association between low serum vitamin D levels and CircS and its components, particularly with short sleep. This suggests a potentially pivotal role of vitamin D in the pathogenesis of Circadian syndrome.

Background: Circadian Syndrome (CircS) encompasses a range of cardiometabolic risk factors that contribute to an increased susceptibility to cardiovascular diseases and type 2 diabetes. Understanding the factors that underpin CircS is essential. This study primarily aims to examine the association between hypothyroidism and CircS in adults. A secondary analysis compares this association with that between hypothyroidism and Metabolic Syndrome (MetS). Additionally, the dose–response relationship between serum free thyroxine (FT4) levels and CircS probability is explored. Methods: This cross-sectional study includes 4050 National Health and Nutrition Examination Survey (NHANES) participants (2007–2012). Hypothyroidism was classified into (1) drug-managed, (2) non-drug-managed (NDM) primary, and (3) NDM central hypothyroidism, based on self-reported medication use and serum TSH/FT4 levels. CircS was defined as having ≥5 of its eight components, including MetS criteria, depression, short sleep, and non-alcoholic fatty liver disease. Results: Our results showed that hypothyroidism was significantly associated with CircS (OR: 1.58, 95% CI 1.26–1.98) and MetS (OR: 1.19, 95% CI 1.01–1.42). An inverse, non-linear relationship between serum FT4 levels and the probability of CircS was observed. Conclusions: The results underscore a significant association between hypothyroidism and CircS and MetS, with FT4 levels inversely related to CircS probability. These findings highlight hypothyroidism’s potential role in CircS pathogenesis and prevention.

Background: Head and neck cancers (HNCs) represent a global health burden, with high morbidity and mortality largely driven by late-stage diagnosis and heterogeneous clinical outcomes. Reliable biomarkers are needed to improve early detection, prognostic stratification, and therapeutic decision-making. This study evaluates the diagnostic and prognostic value of chemokines in HNCs and identifies candidates with clinical relevance. Methods: A comprehensive literature search was conducted on 28 March 2026 across PubMed, Embase, Scopus, Web of Science, and EBSCO. Observational studies involving patients or biological samples with confirmed HNCs were included if they evaluated chemokines as diagnostic or prognostic biomarkers. Risk of bias was assessed using the Newcastle–Ottawa Scale (NOS) for prognostic studies and the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool for diagnostic studies. Meta-analyses were performed for chemokines evaluated in ≥3 studies using the inverse-variance heterogeneity model. Results: Forty-four studies encompassing 7294 participants were included. Prognostic findings were heterogeneous across biomarkers. MIP-3α demonstrated consistently significant associations with poorer survival outcomes. In contrast, IL-8, CXCL10, and CXCR4 showed inconsistent or predominantly non-significant associations with overall survival (OS), disease-free survival (DFS), and locoregional control (LRC). For diagnostic performance, IL-8, in saliva, demonstrated relatively high sensitivity and specificity for oral squamous cell carcinoma. Chemerin showed high diagnostic accuracy, although evidence remains limited. Conclusions: Certain chemokines show potential as diagnostic and prognostic biomarkers in HNCs. However, heterogeneity across tumor types, samples, and methodologies limits evidence. Larger, well-designed studies are needed to validate their clinical utility in risk stratification and personalized management of HNCs.