Over a median follow-up of 4.2 years, 792 incident syndrome cases were identified.
Higher exposure to light at night is associated with an increased risk of CKM syndrome (HR = 1.46).
Increased levels of nitrogen dioxide (NO₂), particulate matter (PM), nitrate (NO₃⁻), and ammonium (NH₄⁺) are independently linked to elevated CKM risk.
Significant interactions between light at night and various air pollutants suggest a compounded effect on CKM syndrome risk.
Joint exposure to high light at night and high particulate matter is associated with a 56.3% increased risk of CKM syndrome.
Findings indicate a need for multi-factor assessments in future CKM syndrome research.
Simplified
BACKGROUND: Cardiovascular-kidney-metabolic () syndrome, characterized by interconnected cardiovascular, renal, and metabolic dysfunctions, poses a growing global health burden. While both light at night (LAN) and air pollutants have independently been linked to adverse health outcomes, their synergistic and joint effects on CKM syndrome risk remain poorly understood. This study aimed to assess the independent, interactive, and joint associations of LAN, air pollutants, and PMcomponents with CKM syndrome. 2.5
METHODS: Data from 4,361 participants aged ≥ 45 years in the China Health and Retirement Longitudinal Study (CHARLS, 2011-2015) were analyzed. Cox proportional hazards regression models were employed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for CKM syndrome risk. Multiplicative and additive interactions between LAN and air pollutants were assessed using likelihood ratio tests and relative excess risk due to interaction (RERI). Joint effects were evaluated by categorizing exposures into tertiles.
RESULTS: Over a median follow-up of 4.2 years, 792 incident CKM syndrome cases were identified. Adjusted models indicated that higher LAN exposure (highest vs. lowest quartile: HR = 1.46, 95% CI: 1.18-1.80) and increased levels of NO₂ (HR = 1.44, 95% CI: 1.18-1.75), PM(HR = 1.49, 95% CI: 1.19-1.87), PM(HR = 1.75, 95% CI: 1.40-2.18), NO₃⁻ (HR = 1.42, 95% CI: 1.15-1.75), and NH₄⁺ (HR = 1.42, 95% CI: 1.15-1.75) were independently associated with elevated CKM risk. Significant multiplicative interactions were observed between LAN and all pollutants except O₃, NO₃⁻, and NH₄⁺ (P for interaction < 0.05). In the additive interaction analysis, the RERI values ranged from 0.158 to 0.792, indicating a significant synergistic effect between LAN and air pollutants, which increases the risk of CKM syndrome. Joint exposure analysis showed that the combination of high LAN and high PM₁₀ increased CKM risk by 56.3% (HR = 1.563, 95% CI: 1.092-2.238), while moderate co-exposure to LAN and PMelevated risk by 33.4% (HR = 1.334, 95% CI: 0.872-2.041). 2.5 10 2.5
CONCLUSION: This study provided evidence that LAN, air pollutants, and PMcomponents were positively associated with CKM syndrome, and significant synergistic and joint effects existed, increasing the risk of CKM syndrome in older adults. These results highlighted the urgency of comprehensive environmental intervention measures and emphasized the necessity of incorporating multi-factor joint exposure assessment in future CKM syndrome research. 2.5
Key numbers
1.46
Increase in Syndrome Risk (LAN)
HR for highest vs. lowest quartile of LAN exposure
1.75
Increase in Syndrome Risk (PM)
HR for highest quartile of PM exposure
1.563
Increase in Syndrome Risk (Joint Exposure)
HR for high LAN and high PM₁₀ exposure
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Declarations. Ethics approval and consent to participate: CHARLS received ethical approval from Peking University (IRB00001052-11015). Participants provided informed consent, with data anonymized for confidentiality. This study used de-identified secondary data and adhered to the ethical principles outlined in the Declaration of Helsinki. The research protocol for this paper was reviewed and approved by the institutional review board of Xinxiang Medical University (No: XYLL-2019072). No further ethical approval was required for the analysis of this anonymized dataset. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.
