In the course of her long life, Katherine Closson traveled, taught school, rebuilt aircraft engines and helped start a stock brokerage firm, but until two years ago, Closson, then 98, had never participated in a scientific study.
That’s when researchers from the Lighting Research Center at Rensselaer Polytechnic Institute (RPI) came to her assisted living facility in Troy, N.Y., outfitted her lamps with bright, bluish-white bulbs and placed them on timers for daytime lighting. They wanted to see whether light of a particular intensity and color might help synchronize the residents’ circadian rhythms—the internal clock our bodies use to manage everything from our sleep-wake cycles to our digestive and cardiovascular systems.
“I loved the blue light,” says Closson, who wore a wrist monitor that measured how soundly she slept during the study. “All the bulbs in my room now are blue.”
The small study, conducted by Mariana Figueiro, an assistant professor at RPI and a program director with the center, was part of ongoing research into whether targeted light therapy can alleviate sleep problems in older people and Alzheimer’s patients without the use of drugs. The research has shown that subjects like Closson sleep more soundly for as much as 90 percent of the night, after receiving regular light stimulation.
“It was incredible,” Figueiro says of the study subjects. “They said, ‘For the first time in years I was able to sleep through the night.’ ”
Scientists have known for years that the body’s internal clock requires regular stimulation by natural light to help keep it in sync with the rising and setting sun. But in older people, changes in the eye prevent sufficient amounts of the optimal blue wavelengths of light from reaching the retina.
Here comes the sun
“They don’t get enough light to maintain the synchronization between the solar day and their internal clock,” Figueiro says. That may explain why between 40 and 70 percent of people over the age of 65 report chronic sleep problems, according to an earlier study.
The promise of a good night’s sleep is but one outgrowth of new research into the body’s circadian rhythms. Chronically disrupted circadian cycles are believed to contribute to obesity, diabetes, depression, heart disease and even cancer. Now, as scientists gain a deeper understanding of how the system functions on a molecular level, they hope to develop drugs to reset the body’s rhythms and optimize health.
Paolo Sassone-Corsi, a molecular biologist at the University of California, Irvine, recently published a groundbreaking study showing that a cellular protein called SIRT1, which is known to slow aging and improve metabolic efficiency, interacts with another protein called CLOCK, which regulates the body’s circadian rhythm.
How to set the body’s clocks
“We found the molecular link between the clock and the aging machinery in the cell,” says Sassone-Corsi. “Conceptually, it’s a completely novel thing.” His discovery opens the door to using new compounds that mimic the effects of resveratrol, a natural substance found in red wine that activates SIRT1, to help regulate the circadian system. It also implies that other factors that influence our metabolism—such as diet—may affect our daily rhythms.
Our internal timekeeping system really consists of multiple clocks—a master clock in the brain synchronizes clocks found in tissues throughout our body. The daily cycle of light and darkness registers with cells in our retina to stimulate the release of melatonin, which helps us sleep soundly, Sassone-Corsi says.
In young people melatonin spikes at much higher levels than in older people, which may help explain why we tend not to sleep as soundly as we age, he explains.