Are We Measuring the Right Light?
“It’s a good article and it’s got a good message, but I have some caveats to that,” said George C. Brainard, PhD, director, Light Research Program, Thomas Jefferson University in Philadelphia, Pennsylvania, and a pioneer in the study of how light affects biology including breast cancer in night-shift workers.
The biggest caveat, and one acknowledged by the authors, is that the study didn’t measure indoor light exposure and relied instead on satellite imaging.
“They’re very striking images, but they may not be particularly relevant. And here’s why: People don’t live outdoors all night,” Dr. Brainard said.
Instead, people spend much of their time at night indoors where they’re exposed to lighting in the home and from smartphones, laptops, and television screens.
“It doesn’t invalidate their work. It’s an important advancement, an important observation,” Dr. Brainard said. “But the important thing really is to find out what is the population exposed to that triggers this response, and it’s probably indoor lighting related to the amount and physical characteristics of indoor lighting. It doesn’t mean outdoor lighting can’t play a role. It certainly can.”
Reached for comment, Erik Musiek, MD, PhD, a professor of neurology whose lab at Washington University School of Medicine in St. Louis, Missouri, has extensively studied circadian clock disruption and Alzheimer’s disease pathology in the brain, said the study provides a 10,000-foot view of the issue.
For example, the study was not designed to detect whether people living in high light pollution areas are actually experiencing more outdoor light at night and if risk factors such as air pollution and low socioeconomic status may correlate with these areas.
“Most of what we worry about is do people have lights on in the house, do they have their TV on, their screens up to their face late at night? This can’t tell us about that,” Dr. Musiek said. “But on the other hand, this kind of light exposure is something that public policy can affect.”
“It’s hard to control people’s personal habits nor should we probably, but we can control what types of bulbs you put into streetlights, how bright they are, and where you put lighting in a public place,” he added. “So I do think there’s value there.”
At least 19 states, the District of Columbia, and Puerto Rico have laws in place to reduce light pollution, with the majority doing so to promote energy conservation, public safety, aesthetic interests, or astronomical research, according to the National Conference of State Legislatures.
To respond to some of the limitations in this study, Dr. Voigt-Zuwala is writing a grant application for a new project to look at both indoor and outdoor light exposure on an individual level.
“This is what I’ve been wanting to study for a long time, and this study is just sort of the stepping stone, the proof of concept that this is something we need to be investigating,” she said.
Dr. Voigt-Zuwala reported RO1 and R24 grants from the National Institutes of Health (NIH), one coauthor reported an NIH R24 grant; another reported having no conflicts of interest. Dr. Brainard reported having no relevant conflicts of interest. Dr. Musiek reported research funding from Eisai Pharmaceuticals.
A version of this article first appeared on Medscape.com.