Nighttime outdoor light, air pollution linked to elevated stroke risk
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Key takeaways:
- High levels of exposure to artificial outdoor light at night and air pollution were associated with elevated risk for stroke.
- The link was stronger for ischemic stroke than hemorrhagic stroke.
In a prospective cohort study, excessive exposure to outdoor artificial light at night and air pollution were associated with elevated risk for stroke, researchers reported in Stroke.
“Despite significant advances in reducing traditional cardiovascular risk factors such as smoking, obesity and type 2 diabetes, it is important to consider environmental factors in our efforts to decrease the global burden of cardiovascular disease,” Jian-Bing Wang, PhD, a researcher in the departments of public health and endocrinology at the Children's Hospital, Zhejiang University School of Medicine and the National Clinical Research Center for Children’s Health in Hangzhou, China, said in a press release.
Wang and colleagues analyzed data from 28,302 participants enrolled in the Yinzhou cohort, consisting of residents of Yinzhou district, Ningbo City, China (mean age, 62 years; 59% women).
The researchers assessed outdoor light at night and air pollution by satellite-derived images and land-use regression models. Cerebrovascular events were determined by medical records and death certificates. Participants were stratified into quartiles by exposure to outdoor light at night, particulate matter with aerodynamic diameter of 2.5 µm or less (PM2.5), particulate matter with aerodynamic diameter of 10 µm or less (PM10) and NO2.
During 127,877 person-years of follow-up, the researchers identified 1,278 cases of cerebrovascular disease, including 777 ischemic strokes and 133 hemorrhagic strokes.
In single-exposure models, the HR per interquartile range increase for cerebrovascular disease was 1.17 (95% CI, 1.06-1.29) for outdoor light at night, 1.25 (95% CI, 1.12-1.39) for PM2.5, 1.14 (95% CI, 1.06-1.22) for PM10 and 1.21 (95% CI, 1.06-1.38) for NO2, according to the researchers.
The results were similar for ischemic stroke, but there was no relationship between hemorrhagic stroke and exposure to outdoor light at night or air pollution.
In multiple-exposure models, the relationship between exposure to outdoor light at night or air pollution and cerebrovascular disease persisted, but the relationship between exposure to outdoor light at night or air pollution and ischemic stroke did not, the researchers wrote.
“Our study suggests that higher levels of exposure to outdoor artificial light at night may be a risk factor for cerebrovascular disease,” Wang said in the release. “Therefore, we advise people, especially those living in urban areas, to consider reducing that exposure to protect themselves from its potential harmful impact. We need to develop more effective policies and prevention strategies to reduce the burden of disease from environmental factors such as light as well as air pollution, particularly for people living in the most densely populated, polluted areas around the world.”
Reference:
- More exposure to artificial, bright, outdoor nighttime light linked to higher stroke risk. https://newsroom.heart.org/news/more-exposure-to-artificial-bright-outdoor-nighttime-light-linked-to-higher-stroke-risk. Published March 25, 2024. Accessed March 25, 2024.
Perspective
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Daniel T. Lackland, DrPH, FAHA, FACE
The air pollution findings are consistent with other studies. The artificial outdoor nighttime light findings with stroke I feel are very premature and require considerably more study and investigation.
The light-related results could be a chance finding. Given the relative large sample size, such findings could be detected but simply due to chance. Also, there could be something at play with the stroke cases — which were significantly more likely to be related to hypertension, diabetes and other known risk factors for stroke. Further, the proposed biological mechanisms for artificial outdoor nighttime light and stroke are only speculation and not evidence-based.
Before focusing on mitigation based on the results of this observational study, considerably more research and re-analyses should be completed. This should include detailed quality assessment of the definition and quantification of artificial outdoor nighttime light; research into the potential biological mechanisms of artificial outdoor nighttime light and stroke risks; and assessment in other populations to replicate the results.
While the results with artificial outdoor nighttime light are interesting and perhaps hypothesis-generating, it is critical to focus on the traditional known risk factors for stroke, including hypertension, that are evidence-based with proven interventions, and that were confirmed as risk factors for stroke in this study.
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