Exposure to bright artificial light between dusk and bedtime can reduce the quality of your sleep and may increase the risk of high blood pressure and diabetes, new research has found.
Researchers followed 116 healthy participants, aged 18 to 30, who were exposed to either bright room light or dim light for eight hours before bedtime for five consecutive days. Blood plasma was collected every 30 to 60 minutes, to check the volunteers' levels of melatonin, a hormone produced at night by the pineal gland in the brain.
Melatonin regulates the sleep-wake cycle and has been shown to regulate blood pressure and body temperature.
The study found that exposure to bright room light before bedtime shortened the duration of melatonin production by about 90 minutes, compared with exposure to dim light. In addition, exposure to bright room light during the usual hours of sleep suppressed melatonin by more than 50%.
The study was published in Journal of Clinical Endocrinology & Metabolism.
"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," study author Joshua Gooley, PhD, of Brigham and Women's Hospital and Harvard Medical School in Boston, said in a news release from the Endocrine Society.
"Further research is still needed to both substantiate melatonin suppression as a significant risk factor for breast cancer and determine the mechanisms by which melatonin regulates glucose metabolism," Dr. Gooley added.
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