Does outdoor light contribute to ovarian cancer mortality? Insights from a case-control study

Unfavorable light environments, including artificial light at night (ALAN) and ultraviolet B (UVB) radiation, may be linked to ovarian cancer, but this association remains uncertain. A multicenter case-control study in Northeastern China was performed. Using propensity score matching, we matched individuals who died from other cancers with controls in a 1:1 ratio. Exposure levels were determined by monthly average outdoor ALAN exposure (0.5 ×0.5 km), UVB radiation (0.25°×0.25°), and PM_2.5 (1 ×1 km) based on each participant's residential address. Conditional logistic regression models were employed to analyze the association between light exposure (1-5 years prior to death) and ovarian cancer mortality. A total of 2159 ovarian cancer deaths and an equal number of controls were included in the study. The average exposure of ALAN and UVB over the 5 years prior to death ranged from 0.1 to 130.3 nw/cm²/sr and 29.1-53.4 W/m², respectively. ALAN exposure was positively associated with ovarian cancer mortality. For example, with 5-year exposure, compared to the lowest quintile (Q1), the hazard ratios (HR) for the second to fifth quintiles (Q₂-Q₅) were 1.51 (95 % CI: 1.13-2.02), 1.69 (95 % CI: 1.23-2.33), 1.79 (95 % CI: 1.29-2.49), and 1.67 (95 % CI: 1.20-2.33), respectively. However, UVB exposure showed only suggestive evidence of a protective effect. Additionally, PM_2.5 exposure emerged as a significant risk factor for ovarian cancer mortality in urban populations. ALAN exposure may serve as a risk factor for ovarian cancer mortality, while PM_2.5 exposure also appears to be a significant risk factor in urban areas.