MedicalResearch.com Interview with:
Lead author: Yong-Moon (“Mark”) Park, MD, PhD
National Institute of Environmental Health Sciences
Senior author: Dale P. Sandler, PhD
Chief, Epidemiology Branch, National Institute of Environmental Health Sciences
National Institutes of Health
MedicalResearch.com: What is the background for this study?
Response: A few studies had suggested that exposure to artificial light while sleeping was associated with obesity. However, the previous studies were cross-sectional, so we really do not know which came first – exposure to artificial light while sleeping or obesity. Another problem was that previous studies did not fully account for other characteristics that could affect this association, such as sleep duration and quality, calorie intake and dietary patterns, and physical activity.
We studied nearly 44,000 women ages 35-74 from across the US who are enrolled in the Sister Study cohort. Women had body weight characteristics measured at baseline and provided self-reported information on weight at baseline and follow-up – on average 5.7 years later.
MedicalResearch.com: What are the main findings?
Response: We found that when the study started, women who had been exposed to artificial light at night while sleeping were more likely to be overweight or obese than women who were not exposed to light at night
Importantly we showed that women who were exposed to light at night while sleeping were also more likely to gain weight or become overweight or obese over time.
The results varied with the level of exposure to artificial light at night while sleeping. For example, using a small nightlight was not associated with weight gain, but women who slept with a light or television on were
- 17% more likely to gain 5 kilograms, approximately 11 pounds or more over the follow-up period.
- 22% more likely to become newly overweight (among those not overweight at baseline)
- 33% more likely to become newly obese (among those not obese at baseline)
MedicalResearch.com: What should readers take away from your report?
Response: Cutting off lights at bedtime could reduce women’s chances of becoming obese.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: The use of smartphones, tablets and laptops has increased dramatically as has use of these devices in the bedroom at night. We did not study the use of these devices. Evaluating their use – and the impact of sleeping with them on in the bedroom- is an important next step. Thus, the role of short wavelength light (e.g., blue light)-emitting electronic devices in relation to weight gain and risk of obesity should be explored in future research. Studies will need to account for changing patterns of exposure over time. Future studies should also include objective information on light intensity (e.g., light emitting diode, fluorescent, or incandescent), as well as wavelength (e.g., blue or red), and how long and when women have the lights on.
MedicalResearch.com: Is there anything else you would like to add?
Response: It is important to note that our results were from an observational study and our information on light exposure and weight gain are based on self-reported information. This limits us from saying that our results are definitive. But, our results do suggest that reducing exposure to artificial light at night while sleeping might be a useful strategy to prevent obesity. This recommendation is consistent with other recommendations related to getting a good night’s sleep.
Unhealthy high-calorie diet and sedentary behaviors have been the most commonly cited factors to explain the continuing rise in obesity. This study highlights the importance of exposure to artificial light while sleeping and gives women who sleep with lights or the television on a way to improve their health.
We have no conflicts of interest to disclose.
Park YM, White AJ, Jackson CL, Weinberg CR, Sandler DP. Association of Exposure to Artificial Light at Night While Sleeping With Risk of Obesity in Women. JAMA Intern Med. Published online June 10, 2019. doi:10.1001/jamainternmed.2019.0571
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