Lowering The Light Could Lower Your Risk of Diabetes, High Blood Pressure

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A small new study that will appear in the March issue of the Journal of Clinical Endocrinology & Metabolism found that exposure to electrical light at night before bed suppresses the sleep-inducing hormone melatonin, which also helps regulate blood pressure. Previous research discovered that true insomniacs often face high blood pressure problems.. “On a daily basis, millions of people choose to keep the lights on prior to bedtime and during the usual hours of sleep,” says Joshua Gooley, PhD, a lecturer from the sleep medicine division of Brigham and Women’s Hospital in Boston. “Our study shows that this exposure to indoor light has a strong suppressive effect on the hormone melatonin. This could, in turn, have effects on sleep quality and the body’s ability to regulate body temperature, blood pressure, and glucose levels.”

The details: Researchers evaluated 116 adults between the ages of 18 and 30 years old, exposing them to either a regular room light or dim lighting for the eight hours leading up to bedtime. They did this for five days in a row. To measure the concentration of melatonin in the participants, researchers inserted arm catheters into the adults and measured blood levels of the hormone every half hour to hour. Exposure to regular light pre-shut-eye cut into melatonin-making time by 90 minutes, compared to the group exposed to dimmer lighting. Participants who were exposed to room lighting during times when they usually were sleeping experienced a 50-percent reduction in melatonin production. “Given that chronic light suppression of melatonin has been hypothesized to increase relative risk for some types of cancer, and that melatonin receptor genes have been linked to type 2 diabetes, our findings could have important health implications for shift workers who are exposed to indoor light at night over the course of many years,” says Gooley, noting that more research on melatonin suppression and health risks is warranted.

What it means: While it’s unlikely that most people will totally cut themselves off from artificial lighting after dusk and before bedtime, there are a number of things that can help keep your body’s natural melatonin production in check. While more studies are needed to be sure of the effect of nighttime light exposure’s links to diabetes and high blood pressure, other studies have associated chronic nocturnal light exposure with cancer, so it’s best to make smart lighting choices for your individual situation.

Here’s how to bring better sleep into your bedroom:

1. Be conscious of color and Kelvins. Warmer lights like incandescents, or bulbs with a similar illumination, are better for your sleep than lights with a bluish tint; it’s the blue-tinted white light that suppresses melatonin the most. So favor redder or warmer lights in the evening. Incandescent lights may have a lesser effect on our body’s natural sleep hormone compared to CFLs or LED lights; however, they are major energy hogs. So if you’re in the market for environmentally friendly bulbs, choose ones that don’t put off as much blue light. It’s the blue light that messes most with melatonin production. For lighting in the bedroom, or other areas of the house where you frequently spend time afer the sun sets, check the package to see the bulbs’ Kelvins (k), a measure of color temperature. Lower temperatures represent warmer light. For instance, warm light, similar to an incandescent bulb’s, registers at about 2,700 k, while 3,500 k creates a cooler light. “CFLs have peaks in the blue, green, and red ranges, so they fall in the middle in terms of spectrum,” explains Lockley. LED bulbs are the most environmentally friendly lighting choice, but they tend to be bluer-looking. The good news is that companies are starting to manufacture warmer-looking LEDs, and they are becoming more affordable, too. Don’t stress too much if you can’t find the perfect bulb. “The major thing is to dim the lights as far as possible, regardless of the lamp type,” says Lockley. “The light level should be as low as possible, but still enough that you can read.”

2. Cut bright light close to bedtime. “In the one to two hours before bed, avoid bright light and make an effort to dim the lights,” suggests Steven Lockley, PhD, assistant professor of medicine in the division of sleep medicine at Harvard Medical School.

3. Make sure your kids make adequate melatonin. If you have children, set a technology curfew, and shut off TVs, computers, and cellphones at least an hour before bed. A half hour before bedtime, dim the lights, or turn off the main lights and turn on a lamp equipped with a dimmer bulb.

4. Don’t let your bedroom be TV land. “There should not be a TV in the bedroom, to avoid light from the TV before bed. And computers and other electronics should also not be in the bedroom,” says Lockley. Instead, he recommends making an effort to do something relaxing in dim light before bed, such as breathing exercises, meditation, reading, taking a hot bath, or indulging in a non-caffeinated drink. If you do watch TV at night, Lockley recommends sitting as far away from the screen as possible.

5. Snuff out other culprits. Ambient light from street lights, alarm clocks, and other electronics that glow throughout the night can mess with your sleep, especially blue-colored lights. “Blue light is more alerting and has more melatonin suppression effect than the same number of photons of red light, so avoiding blue light in the evening and night is advisable,” says Lockley. Turn your alarm clock toward the wall or cover it with a piece of fabric, wear an eye mask, or hang blackout shades and curtains to make sure you’re exposed to enough darkness throughout the night.


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