Sleeping with a Nighlight Could Lead to Weight Gain for Women

Sleeping with a light on has been linked with weight gain in women, according to a new study. 

The study, published in the Journal of the American Medical Association, analyzed 43,722 women and found that sleeping with an artificial light source at night was “significantly associated with increased risk of weight gain and obesity.” This is also especially true for women who had a light or a television on in the room while sleeping. 

The study found that any kind of artificial light on at night, even a small nightlight or light outside of the room, were associated with weight gain. Specifically, sleeping with a television or light in the room was associated with gaining five kilograms over a five year period. It was also found that sleeping with a night light could lead to 22% chance of becoming overweight and a 33% chance of being obese. 

The women who participated in the study self-reported their sleeping habits and were classified into four: (1) no light, (2) small nightlight, (3) light outside the room, (4) light or television in the room. Their BMI (Body Mass Index) was also measured at the beginning of the study. 

The researchers found that women who belong in category 4 or those sleeping with a light or television in the room was associated with gaining 5 kilograms or more and a 10% increase in BMI. However, the senior Dale Sandler from the National Institute of Environmental Health Science in North Carolina admitted that their data had limitations. “Our data are based on self-reports”, he said. According to Professor Malcolm von Schantz, chronobiology professor at the University of Surrey, the study would have been stronger if the subjects were wearing instruments that measured their activity and the amount of light they were exposed to rather than self-reports. 

Although further research is required to concretely link exposure to nightlight and weight gain, the study did reflect similar results from a separate research which was published in 2016 on the Journal of Clinical Endocrinology and Metabolism. Said research also linked light exposure at night with a 10% increase in BMI over a 10 year period.

“We know that light in the late evening will delay our body clocks. We know from experimental studies in people that light at night affects our metabolism” Professor von Schantz said. “These new findings won’t change the advice to maintain good sleep hygiene and avoid light and electronic distractions in the bedroom”, he added.