Every day people are exposed to hours of artificial light from a variety of sources – computers, video games, office lights and, for some, 24-hour lighting in hospitals and nursing homes.
Now new research in animals shows that excessive exposure to “light pollution” may be worse for health than previously known, taking a toll on muscle and bone strength.
Researchers at Leiden University Medical Center in the Netherlands tracked the health of rats exposed to six months of continuous light compared to a control group of rats living under normal light-dark conditions — 12 hours of light, followed by 12 hours of dark.
During the study, the rats exposed to continuous light had less muscle strength and developed signs of early-stage osteoporosis. They also got fatter and had higher blood glucose levels. Several markers of immune system health also worsened, according to the report published in the medical journal Current Biology.
While earlier research has suggested excessive light exposure could affect cognition, the new research was surprising in that it showed a pronounced effect on muscles and bones. While it’s not clear why constant light exposure took a toll on the motor functions of the animals, it is known that light and dark cues influence a body’s circadian rhythms, which regulate many of the body’s physiological processes.
“The study is the first of its kind to show markers of negatively-affected muscle fibers, skeletal systems and motor performances due to the disruption of circadian clocks, remarkably in only a few months,” said Chris Colwell, a psychiatry professor and sleep specialist at the University of California, Los Angeles, who was not part of the study. “They found that not only did motor performance go down on tests, but the muscles themselves just atrophied, and mice physically became weaker under just two months under these conditions.”
The good news is the effects of artificial light exposure appear to be reversible. When the study rats returned to their natural light-dark cycle, their health issues returned to normal after two weeks.
While the findings of a rat study can’t be translated directly to human health, the data suggest more research is needed into the health effects of artificial light. One concern is the health of patients in hospital intensive care units, elderly people in nursing homes and babies in neonatal units — places where artificial lights often are kept on for 24 hours a day.
“We keep the sickest people in our society under constant light conditions,” said Dr. Colwell.
The research also may have implications for people exposed to hours of light emitted from video games and computers. Studies have shown the blue wavelength light from screens is more disruptive to the body’s circadian system than the red wavelength light that comes from traditional artificial lights.