Independent and combined relationships between nighttime light exposure, air pollution, PM2.5 constituents, greenness and diabetes or high blood sugar: a national prospective cohort study

Aug 15, 2025BMC public health

How Nighttime Light, Air Pollution, and Green Spaces Are Linked to Diabetes and High Blood Sugar in a National Study

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Abstract

Among 11,865 participants, 371 developed (D/HBS) during a median follow-up of 4.0 years.

Nighttime light exposure is associated with a 15% increased risk of D/HBS for each interquartile range increase.
High exposure to particulate matter (PM) and nitrogen oxides (NO) significantly raises the risk of D/HBS, with hazard ratios of 1.46 and 1.44, respectively.
Higher (NDVI) is linked to a 48% reduction in the risk of D/HBS.
Synergistic effects between nighttime light and air pollutants amplify the risk of developing D/HBS.
Air pollutants partially diminish the protective effects of NDVI against D/HBS.

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BACKGROUND: (D/HBS) is a major global public health challenge, with a particularly high burden among middle-aged and older adults in China. While traditional risk factors (e.g., obesity, sedentary behavior) are well-studied, the impacts of environmental factors such as nighttime light (NL), air pollution, and the (NDVI) on D/HBS remain underexplored.

METHODS: Using data from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2015), we included 11,865 participants aged ≥ 45 years without baseline D/HBS. Cox proportional hazards models were employed to evaluate the independent effects of NL, air pollutants (PM, PM, NO, etc.), and NDVI on D/HBS risk, adjusting for confounders. Interaction effects, joint effects, and mediation effects were further analyzed. 1 2.5 2

RESULTS: The median follow-up duration was 4.0 years. Among the 11,865 baseline participants, 371 developed incident D/HBS. NL was significantly associated with increased D/HBS risk (per IQR increase: HR = 1.15, 95% CI: 1.06-1.26). High exposure to PM(Q4: HR = 1.46, 95% CI: 1.06-2.01) and NO(Q4: HR = 1.44, 95% CI: 1.07-1.92) elevated risk, while higher NDVI (Q3: HR = 0.52, 95% CI: 0.37-0.72) showed a protective effect. Synergistic effects were observed between NL and PM(RERI = 0.61, 95% CI: 0.13-1.09) or NO(RERI = 0.59, 95% CI: 0.11-1.08). Mediation analyses indicated that air pollutants, specifically NH(proportion = - 68.3%) and NO(proportion = - 64.1%), partially attenuated the protective role of NDVI. 2.5 2 2.5 3 4 3 -+ -

CONCLUSIONS: NL and air pollution are independent risk factors for D/HBS, with synergistic effects exacerbating disease risk. NDVI confers protection by reducing pollutant exposure. Comprehensive strategies targeting light pollution control, air quality improvement, and optimized green space planning are imperative. Future studies should integrate individualized exposure assessments and elucidate causal environmental-metabolic pathways.

Key numbers

1.15

Increase in D/HBS Risk

Hazard ratio per IQR increase in nighttime light exposure

1.46

High PM Exposure Risk

Hazard ratio for highest exposure quartile of PM

0.52

Protective Effect of Greenness

Hazard ratio for third quartile of

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Independent and combined relationships between nighttime light exposure, air pollution, PM2.5 constituents, greenness and diabetes or high blood sugar: a national prospective cohort study

Abstract

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