A recent study led by surgeon-scientists from the University of Pittsburgh School of Medicine and UPMC has found that exposure to long-wavelength red light is linked to a reduced incidence of blood clots in both humans and mice. This research is published today in the Journal of Thrombosis and Haemostasis.
If confirmed by further clinical trials, these results could contribute to a decrease in blood clots in veins and arteries, which are major contributors to preventable deaths globally.
“The type of light we encounter can affect our biological functions and overall health,” stated Elizabeth Andraska, M.D., the study’s lead author and assistant professor of surgery at Pitt’s Trauma and Transfusion Medicine Research Center, as well as a vascular surgery resident at UPMC. “Our discoveries could pave the way for an affordable therapy that might benefit millions.”
Researchers have long established a link between light exposure and health outcomes. The natural pattern of sunlight influences metabolism, hormone release, blood circulation, and the risk of heart attacks and strokes, which are more common during morning hours compared to night. Andraska and her team examined whether light exposure could impact the blood clotting associated with these health issues.
To explore this, the researchers subjected mice to 12 hours of red, blue, or white light, followed by 12 hours of darkness over a 72-hour period. They measured differences in blood clot formation among the groups. Mice exposed to red light formed nearly five times fewer clots than those exposed to blue or white light. There were no significant variations in activity levels, sleep patterns, eating habits, weight, or body temperature among the groups.
The researchers also reviewed data from more than 10,000 patients who underwent cataract surgery, receiving either traditional lenses that allow full spectrum light or blue light-filtering lenses, which let through about 50% less blue light. They found that cancer patients who used blue light-filtering lenses had a lower risk of developing blood clots compared to those with conventional lenses. This is particularly important given that cancer patients have a ninefold increased risk of blood clots compared to those without cancer.
“These findings unravel a captivating mystery about how the daily light exposure affects our body’s healing responses,” said senior author Matthew Neal, M.D., a professor of surgery at Pitt and co-director of the Trauma and Transfusion Medicine Research Center, who also practices as a trauma surgeon. “Our next goal is to understand the biological mechanisms behind these observations and to assess whether increasing red light exposure in individuals at high risk for blood clots might decrease their risk. Clarifying these findings could drastically reduce deaths and disabilities related to blood clots across the world.”
The study suggests that the optic nerve plays a crucial role—blind mice showed no changes in clotting, and shining light directly on blood did not affect clot formation.
The researchers noted that red light exposure correlates with reduced inflammation and immune activation. For instance, mice that were exposed to red light had lower levels of neutrophil extracellular traps (NETs), which are structures created by immune cells to ensnare harmful microorganisms, but they also ensnare platelets, contributing to clot formation.
Mice exposed to red light exhibited an increase in fatty acid production, which in turn reduces platelet activation. Because platelets play a crucial role in clotting, this naturally leads to a decrease in clot formation.
Discovering how red light induces changes that lessen clotting risk could help researchers develop more effective and user-friendly medications or therapies compared to ongoing red light exposure.
In preparation for clinical trials, the team is designing special goggles to regulate light exposure for participants and is investigating which individuals may benefit the most from red light treatment.
Additional contributors to this research include Frederik Denorme, Ph.D., Robert Campbell, Ph.D., and Matthew R. Rosengart, M.D., all from Washington University in St. Louis; as well as a number of researchers from Pitt, including Christof Kaltenmeier, M.D., Aishwarrya Arivudainabi, Emily P. Mihalko, Ph.D., and others; and Kimberly Thomas, Ph.D., of Vitalant Research Institute.
This study was made possible through funding from several National Institutes of Health grants, the University of Pittsburgh Center for Research Computing, and the American Heart Association, among others.
