How light at night may harm outcomes in cardiac patients

Summary: Night time white lighting in hospital rooms has been linked to higher rates of inflammation, apoptosis and mortality risk for those who have recently experienced a cardiac event.

Source: West Virginia University

In a study funded by the National Institutes of Health, West Virginia University neuroscientists linked white light at night–the kind that typically illuminates hospital rooms–to inflammation, brain-cell death and higher mortality risk in cardiac patients.

Randy Nelson, who chairs the Department of Neuroscience in the WVU School of Medicine, and Courtney DeVries, the John T. and June R. Chambers Chair of Oncology Research at WVU, re-created cardiac arrest in animal models. Doing so temporarily interrupted the brain’s oxygen supply. Then the researchers and their colleagues divided the models into three groups that would spend their nights in–respectively–dim red light, dim white light, and the dark.

After seven nights of this regimen, the researchers evaluated the health of the models’ brain cells. Exposure to white light at night caused multiple poor outcomes. The researchers’ findings are published in Experimental Neurology.

Cardiac arrest was more likely to be lethal for models in the white-light-at-night group, whereas the mortality rate in the red-light-at-night group did not differ from the group that stayed in darkness.

Exposure to white light at night also correlated to greater cell death in the hippocampus–a part of the brain that’s key to memory formation–and more aggressive inflammation overall. In fact, just one dimly illuminated night was enough to cause pro-inflammatory cytokines–tiny proteins critical to immune responses–to surge. This was only the case, however, if the light was white. Red light had no effect.

“When you see long-wavelength, blue light first thing in the morning, those long wavelengths set your circadian clock to precisely 24 hours. The problem is, if you see blue light at night–from your phones, TVs, computers and compact fluorescent lights–they’re disrupting your circadian system all night long. Those lights look white to us, but frankly, they’re mostly blue,” explained Nelson, who–along with DeVries–receives support from the West Virginia Clinical and Translational Science Institute. His previous research has associated nocturnal blue light with higher rates of obesity, metabolic disorders, and depression.

“Clearly light at night is required in patients’ rooms acutely after cardiac arrest and other major health events,” said Laura Fonken, lead author on the study and an assistant professor at the University of Texas at Austin. “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.”

This image shows the orange tinged gaming glasses described in the news relesae
WVU neuroscientists are studying whether wearing glasses with orange lenses at night can improve outcomes in cardiac patients. The glasses filter out blue light, which the researchers tied to inflammation, brain-cell death and greater mortality in a recent study based on animal models. The image is credited to WVU.

To that end, the researchers are exploring whether white light at night provokes a similar physiological response in people. For four nights in a row, they outfit one group of hospitalized cardiac patients in special “gaming glasses” with orange lenses that filter out the troublesome blue light. Wearing the glasses seems to bathe everything in warm, sunset tones. Another group of patients wears identically shaped glasses that have clear lenses, allowing the full spectrum of white light–including blue tones–to pass through.

“The cool thing from our perspective is, we believe these longer-wavelength lights won’t have that detrimental effect, and people will recover faster,” Nelson said. If studies bear out the researchers’ hunch, gaming glasses may be an affordable, practical option for preserving brain function, reducing inflammation and lowering the risk of death in cardiac patients.

About this neuroscience research article

Source:
West Virginia University
Media Contacts:
Cassie Thomas – West Virginia University
Image Source:
The image is credited to WVU.

Original Research: Closed access
“Dim light at night impairs recovery from global cerebral ischemia”
Laura K.Fonken, Tracy A. Bedrosian, Ning Zhang, Zachary M. Weil, A. Courtney DeVries, Randy J. Nelson. Experimental Neurology
Volume 317, July 2019, Pages 100-109 doi:10.1016/j.expneurol.2019.02.008

Abstract

Dim light at night impairs recovery from global cerebral ischemia

Nighttime lighting is one of the great conveniences of modernization; however, there is mounting evidence that inopportune light exposure can disrupt physiological and behavioral functions. Hospital patients may be particularly vulnerable to the consequences of light at night due to their compromised physiological state. Cardiac arrest/cardiopulmonary resuscitation (CA) was used to test the hypothesis in mice that exposure to dim light at night impairs central nervous system (CNS) recovery from a major pathological insult. Mice exposed to dim light at night (5 lx) had higher mortality in the week following cardiac arrest compared to mice housed in dark nights (0 lx). Neuronal damage was significantly greater in surviving mice exposed to dim light at night after CA versus those housed in dark nights. Dim light at night may have elevated neuronal damage by amplifying pro-inflammatory pathways in the CNS; Iba1 immunoreactivity (an indication of microglia activation) and pro-inflammatory cytokine expression were elevated in mice exposed to dim light at night post-CA. Furthermore, selective inhibition of IL-1β or TNFα ameliorated damage in mice exposed to dim light at night. The effects of light at night on CA outcomes were also prevented by using a wavelength of nighttime light that has minimal impact on the endogenous circadian clock, suggesting that replacing broad-spectrum nighttime light with specific circadian-inert wavelengths could be protective. 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.

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