Ever wonder why you feel a little amped up after a nightime outing to a Red Sox game or the glaring lights of New York's Times Square?
Exposure to bright lights at night appears to delay the release of the sleep-inducing hormone melatonin, according to a study of 116 healthy volunteers published last week in the Journal of Clinical Endocrinology & Metabolism. In the study, volunteers who spent 24 hours straight in a room with constant light exposure at night reduced the time their body's released melatonin by 90 minutes a day compared with when they were in rooms with very dim light during the evening and nighttime hours.
Did those bright lights inhibit their sleep? "We're looking at the data on this now," says study co-author Steven W. Lockley, a neuroscientist at Brigham and Women's Hospital. But a disruption in melatonin -- normally released from after sunset until sunrise by the brain's pineal gland, which contains light sensitive cells -- is known to be involved in jet lag and seasonal affective disorder.
It's also thought to play a role in the increased cancer rates among nighttime shift workers, according to the International Agency for Research on Cancer. Melatonin acts like an antioxidant to neutralize cancer-causing free radicals and appears to affect the immune system, possibly by turning on cancer-suppressing genes.
"Those nighttime lights place our bodies in continual summer with long days and short nights," points out Lockley. And, he says, researchers don't yet know what health consequences are resulting from this. "It could be that we need more sleep in the winter than we're getting," he says, "and we're eating more than we need to give ourselves extra energy to make up for the lack of sleep."
Thomas Edison never would have dreamed when he invented the light bulb that he'd be held responsible for the current obesity epidemic!
Still, no one wants to go back to the dark ages, so what's a practical solution? Lockley recommends the following:
1. Take electronic screens out of your bedroom. Ban the TV, iPad, laptop, or Blackberry from your bed at night. The amount of light emanating from screens in close proximity to your face is enough to suppress melatonin production, Lockley says. E-readers like Kindle and back-lit clocks are probably fine since they don't give off much glare.
2. Use dimmer lights closer to bedtime. Turn off the recessed lights with the high-wattage LED bulbs and switch on the desk lamp with a 60-watt bulb. Also sit at least 10 feet away from your TV.
3. Avoid the bathroom light in the middle of the night. Just a minute or two of bright lights when you're half asleep, says Lockley, can be enough to make your brain think it's morning -- at 2 a.m -- leading to a suppression of melatonin production. "You should have enough light glare streaming in through the window to find your way around the bathroom," says Lockley. If your bathroom doesn't have a window, install a nightlight with a red-orange bulb, he suggests. "That color on the light spectrum won't suppress melatonin."
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