Many people feel a sense of fear when night falls, and some even leave a light on to fall asleep, but is this really good for sleep?
Regardless of whether leaving the lights on helps with sleep, a recent study by scientists at the National Institutes of Health (NIH) suggests that leaving the television or lights on before bed may lead to weight gain or obesity. This study, published online in JAMA Internal Medicine on June 10, is the first to find a link between nighttime light during sleep and weight gain in women. The results indicate that turning off the lights before bed can reduce the chances of obesity in women.
This is a cohort study investigating risk factors for breast cancer and other diseases. Researchers surveyed 43,222 women aged 35-74 who had no history of cancer or cardiovascular disease, were not pregnant, and did not work shifts, as these factors can lead to irregular sleep patterns.
The questionnaire primarily inquired about the lighting conditions in the rooms where these women slept, such as whether there were lights present, whether they were indoor or outdoor lights, the intensity of the light, and whether they slept with the television on. In addition, researchers assessed basic information about the respondents before and after the study, including their weight, height, waist circumference, and hip circumference, as well as their body mass index (BMI) and various physiological conditions. Hopefully, this will reveal some insights.
After several years of follow-up research, some findings have finally emerged. The results are quite interesting; researchers discovered that the weight levels of female respondents varied with the intensity of nighttime light. For example, when using a nightlight, the indoor light was dim, so there was no effect on weight. However, if the indoor light was bright, such as with the lights on or the television on while sleeping, weight would increase. The women surveyed generally gained about 5 kilograms during the follow-up period. Outdoor light also had some effect, but not as much as indoor light.
"While poor sleep is itself associated with obesity and weight gain, the effects of light on the body during sleep have not been studied," said Dr. Dale Sandler, director of the National Epidemiology Division at the National Institute of Environmental Health Sciences (NIEHS), who led the study.
One of the paper's co-authors, Dr. Chandra Jackson, also from NIEHS, pointed out that for many people living in urban environments, there is more light at night, so people are exposed to light more often than people living in rural areas. Streetlights, neon signs on shop signs, and various other nighttime light sources all affect the circadian rhythm of melatonin secretion.
Jackson said, "From a genetic perspective, humans are better adapted to sunlight during the day and darkness at night. Exposure to light at night may affect hormone secretion and other physiological processes, thereby increasing the risk of obesity."
Many people know that melatonin is a hormone that can improve sleep quality. It is secreted by the pineal gland in the brain. Melatonin secretion activity increases immediately when a person is in the dark, and stops when in a bright environment. Therefore, nighttime light can also affect melatonin secretion.
Inspired by this study, Dr. Yong-Moon Park, one of the lead researchers, noted that it proposes a highly feasible public health strategy: controlling and reducing nighttime light exposure to lower obesity rates in women. He said, "Previously, unhealthy high-calorie diets and sedentary lifestyles were considered the main causes of obesity, but this study highlights the importance of nighttime light exposure and serves as a reminder to women who like to sleep under lights or television."
Therefore, for those ladies who are on a weight loss journey, sleeping with the lights on might slow you down. Maintaining a good sleep environment, free from the stimulation of light, might actually help you lose weight faster.
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