White light exposure may hinder recovery for heart patients

An animal study published in Experimental Neurology suggests recovery from cardiac arrest is inhibited by exposure to white light—the same kind that normally illuminates hospital rooms.

Researchers triggered cardiac arrest in mice and evaluated their progress based on whether they spent nights in the dark, under dim red light or under dim white light.

After seven nights, mice who were exposed to white light had greater mortality, more aggressive inflammation through pro-inflammatory cytokine expression and more extensive cell death in the hippocampus compared to the other two groups. Red light appeared to have no significant effect on recovery compared to darkness.

“Together, these data indicate that exposure to dim light at night after global cerebral ischemia increases neuroinflammation, in turn exacerbating neurological damage and potential for mortality,” the researchers wrote.

In a press release, the authors said long-wavelength white or blue light at night disrupts the circadian system, essentially throwing the body’s internal clock out of whack. But the fact that reddish light wasn’t as harmful in this study points toward a potential solution if the results are also proven in humans.

“Clearly light at night is required in patients’ rooms acutely after cardiac arrest and other major health events,” lead author Laura Fonken, PhD, an assistant professor at the University of Texas at Austin, said in the release. “Our data suggest that a relatively simple shift—changing the light color from broad-spectrum white to a red hue—benefits outcomes in an animal model of cardiac arrest. If this also occurs in clinical populations, then it would be important because it would not require complicated clinical trials to implement for patients and could improve recovery from various other health events that require hospital stays.”

The researchers said they’re conducting a study in which heart patients will wear a pair of clear or orange-tinted “gaming glasses” to test whether this physiological response also applies to humans. The clear lenses will let through the blue or white light, while the orange lenses are designed to filter it out and more closely approximate the warm tones that were deemed harmless in the mouse study.