Heart disease, depression and night lights

Sleep is proving more elusive than ever for Americans, even as evidence mounts that lost sleep puts us at greater risk for everything from depression to diabetes to heart disease.

According a recent Wall Street Journal piece, a National Sleep Foundation survey found that 51 percent of people aged 19 to 29 years, and 43 percent of 30-somethings, say they rarely or never get a good night’s sleep on weekdays.

In my case, quality sleep is often interrupted as massive Alabama thunderstorms or bad dreams chase my 5-year-old into our bed. In the case of nightmares, one thing we've tried is tucking our son back into bed in the gentle glow of his turtle-shaped night light.

Then I read this article in Science News by Janet Raloff (@jarsciencenews) that says exposing him to light when he’s sleeping could be bad for his mind and body.

I ran the idea of night light as health threat by Karen Gamble, Ph.D., assistant professor in the Behavioral Neurobiology Division of the Department of Psychiatry in the UAB School of Medicine. It turns out that the connections between nightly light exposure, circadian rhythm and disease risk are hot research areas, and that she is recruiting for a related study in shift-working nurses right now.

“When environmental and bodily rhythms are out of sync, circadian misalignment results, which can contribute to increased risk of cardiometabolic problems and cancer, as well as to mental disorders,” says Gamble.

Life on earth evolved for eons based on a rhythm: day and night, light and dark, wake and sleep, eat and fast. Researchers in recent years even have discovered a genetic feedback loop in our cells that operates in roughly 24-hour cycles, with links to hundreds of gene pathways, many of which regulate how our cells process energy. In other words, it looks like we are wired at the genetic level to sleep at night, and to wake up and eat during the day -- and that bucking those patterns may have consequences.

“Think about the airlines and other industries that rely on light for their nightly function,” says Gamble. “Lighting at night in most hospitals is very bright for patients, as well as the workers. It will be interesting to see the results of future studies that finally tell us whether or not hospitals brightly lit 24/7 slow patient recovery.”

And what about hospital workers? Gamble has begun a study looking at the health of shift-work nurses, who are “greatly exposed” to the effects of light at night and to chaotic sleeping patterns. Most hospitals employ a “standard” schedule of several consecutive 12-hour shifts followed by several days off.  Because 97 percent of nurses choose to go back to sleeping at night on their days off, her team is particularly interested in how these nurses choose to switch back and forth and how these strategies affect their health and mood.

Experiments will measure rhythms of activity, hormones and body function to determine how sleep patterns affect the nurses’ degree of circadian misalignment. The research team also will collect data on chronic light exposure over this period to assess how light at “night” affects adaptation to shift work.

Gamble says those interested in circadian genetic clocks, nightlights and sleep patterns should take a look at this Howard Hughes Medical Institute webcast series or the Circadian Rhythm Laboratory site by the University of South Carolina. Also, check out the science behind using special glasses to block out the blue light portion of your artificial lighting before bed, which may raise levels of the sleep hormone melatonin.


About the blogger

Greg Williams @gregscience @themixuab is research editor within Media Relations at the University of Alabama at Birmingham.