The disruptive effects of artificial light on sleep are well documented, and have received an increasing amount of attention in recent years -- with good reason. Nighttime exposure to artificial light -- which for the great majority of us happens without much thought or awareness -- disrupts the body's circadian rhythm, altering the 24-hour biological clock that controls our sleep-wake cycle. In addition to wreaking havoc with sleep, disruptions to circadian rhythms also have been associated with a number of serious diseases, including cancer, diabetes, depression and heart disease.
In particular, research in recent years has shown that blue wavelength light is especially harmful to circadian rhythm function. Studies have shown that blue wavelength light has uniquely harmful effects on humans and suppresses melatonin levels more vigorously than other light wavelengths. Unfortunately, many energy-efficient light sources produce high concentrations of blue light. Blue light is emitted by electronic devices, energy-efficient light bulbs, and other common light sources.
Research investigating blue-light blocking -- most often in the form of goggles that filter out this particular wavelength of light -- has shown promise. A new study of cataract patients indicates that artificial lens implants can help improve sleep. Scientists at China's Sichuan University studied the effects of blue-light blocking artificial lenses implanted during cataract surgery. The study involved 40 patients who required surgery for cataracts in both eyes. Cataract surgery commonly involves removal of the eye's damaged lens and insertion of an artificial lens. Cataracts are a common condition among older adults -- approximately 60 percent of people over the age of 60 experience cataracts. The study subjects -- 26 women and 14 men, with an average age of 74 -- were given artificial lenses with blue-light blocking capability. Researchers assessed patients sleep quality before surgery and again two months after surgery. They found patients' sleep had improved significantly across several measures:
- Patients were sleeping more during the night.
- Their sleep quality had improved.
- Their levels of daytime dysfunction due to sleepiness had diminished.
- The number of subjects who met the criteria for "poor sleepers" had decreased.
Lens replacement surgery is necessary for cataract patients. But there are other, less-invasive ways to filter out blue-light that are also being investigated by sleep scientists. Research has shown the benefits to sleep of manipulating and controlling exposure to blue light:
- A study of 20 adults who wore either blue-light blocking or ultraviolet-light blocking glasses for three hours before sleep found that both sleep quality and mood improved among those in the group who wore blue-light blocking glasses, compared to the ultraviolet-light blocking group.
- Shift workers are at especially high risk for circadian rhythm disruptions because of their non-traditional schedules. In a study by scientists at Quebec's Universite Laval, nightshift workers used blue-light blocking glasses at or near the end of their overnight shifts for four weeks. At the end of study period, their overall sleep amounts increased, as did their sleep efficiency.
- While nighttime exposure to blue wavelength light is damaging to circadian rhythms, exposure to blue light isn't always detrimental. Daytime exposure to blue light can stimulate alertness and help sleep later on. A study of 94 office workers found that daytime exposure to blue light during work hours resulted in improvements both to sleep and to daytime functioning, compared to exposure to white light. Subjects who were exposed to blue light experienced improvements to daytime alertness, mood, and concentration. These subjects also experienced decreases in daytime sleepiness and they slept better at night.
This area of research is critically important, and I expect we will see a great deal more investigation into the effects of blue wavelength light on sleep and health. But you don't need special goggles or eye lens implants to protect your circadian rhythms and your sleep from the negative effects of artificial light. Here are some low-tech suggestions that can help you:
- Limit exposure to artificial light in the hours before bed. The last 1-2 hours before bed should be a time of winding down and preparing for sleep. Decreasing your exposure to light is an important part of this process. You don't have to sit in a pitch-black room, but you should think about beginning to limit your exposure to bright lights, whether from your computer screen or your television. Reading under moderate lamplight is fine. If you're using a tablet to read, bring the screen's brightness level down. Make the last 60 minutes of your bedtime ritual electronics-free -- and keep electronic gadgets and devices out of the bedroom altogether.
- Get light exposure during the day. Daytime exposure to light -- both sunlight and artificial light -- can help strengthen circadian rhythms and boost daytime alertness, leaving you better prepared to sleep when the time comes.
- If you need access to light in the middle of the night, use small nightlights. Rather than switching on hallway or bathroom lights -- and flooding your system with melatonin-suppressing light -- use low-illumination night lights to guide you when you need to get up in the dark.
Being aware of the effects of nighttime exposure to light and making some basic changes to bedtime routines can go a long way toward getting you the darkness you need to sleep well, even in this ever-bright modern age.
Michael J. Breus, PhD
The Sleep Doctor®
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