Research Highlights:
Embargoed until 1 p.m. CT/2 p.m. ET, Monday, March 25, 2024
DALLAS, March 25, 2024 — People continuously exposed to bright, artificial light at night may be at increased risk of developing conditions that affect blood flow to the brain and having a stroke , according to research published today in Stroke , the peer-reviewed scientific journal of the American Stroke Association, a division of the American Heart Association.
Bright, outdoor lights are used at night to enhance the visibility of the environment, improving human safety and comfort. However, the excessive use of artificial light has resulted in about 80% of the world's population living in light-polluted environments, according to the study’s authors.
While previous studies have linked increased exposure to bright, artificial light at night to the development of cardiovascular disease , this is one of the first studies to explore the relationship between exposure to light pollution at night and the potential risk to brain health and 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,” said one of the corresponding authors Jian-Bing Wang, Ph.D., a researcher in the department of public health and department of endocrinology of the Children's Hospital, Zhejiang University School of Medicine and the National Clinical Research Center for Children’s Health in Hangzhou, China.
In a review of 28,302 adults living in China, exposure to residential outdoor nighttime light was assessed by satellite images that mapped light pollution. Cases of stroke were confirmed by hospital medical records and death certificates.
The analysis of data including six years of follow-up with participants found:
Of note, an additional analysis that included both outdoor light at night and pollution found that the associations with increased risk of cerebrovascular disease persisted, except for ischemic stroke.
“Our study suggests that higher levels of exposure to outdoor artificial light at night may be a risk factor for cerebrovascular disease,” Wang said. “Therefore, we advise people, especially those living in urban areas, to consider reducing that exposure to protect themselves from its potential harmful impact.”
Artificial sources of light include fluorescent, incandescent and LED light sources. Continuous exposure to these light sources at night can suppress melatonin production, a hormone that promotes sleep. This can disrupt the 24-hour internal clock in people and impair sleep. People with poor sleep, compared to good sleepers, are more likely to experience worse cardiovascular health over time, according to the study. The American Heart Association’s Life’s Essential 8 includes healthy sleep as one of the eight healthy lifestyle behaviors and health measures that drive optimal cardiovascular health.
“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,” Wang said.
Study background and details:
There were several limitations to the study, including that it did not obtain data on indoor lighting products and shading measures such as blackout curtains used by participants during nighttime. Additionally, satellite-based products rarely capture blue light sources, which may lead to an underestimated association between outdoor light at night and cerebrovascular disease; and the population studied was from one city in China, therefore the findings may not apply to people in other communities with different exposure to outdoor light at night. Larger prospective studies are needed to confirm these findings.
Co-authors, disclosures and funding sources are listed in the manuscript.
Studies published in the American Heart Association’s scientific journals are peer-reviewed. The statements and conclusions in each manuscript are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers and the Association’s overall financial information are available here .
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About the American Stroke Association
The American Stroke Association is devoted to saving people from stroke — the No. 2 cause of death in the world and a leading cause of serious disability. We team with millions of volunteers to fund innovative research, fight for stronger public health policies and provide lifesaving tools and information to prevent and treat stroke. The Dallas-based association officially launched in 1998 as a division of the American Heart Association. To learn more or to get involved, call 1-888-4STROKE or visit stroke.org . Follow us on Facebook , Twitter .
Stroke
Outdoor Light at Night, Air Pollution, and Risk of Cerebrovascular Disease: A Cohort Study in China