A new study released by the American Medical Association's JAMA Internal Medicine on the 10th shows that women who turn on their lights or sleep on TV may have an increased risk of weight gain.
Agence France-Presse reported that the study surveyed nearly 44,000 American women for a five-year follow-up survey and classified them according to their exposure to nighttime artificial light sources; the light source came from the night light, the radio clock, and the light from the street. TV and room lights are available.
One of the key findings is that women who sleep on television or room lights have a 17% increase in the likelihood of gaining 5 kilograms during the study period. This association is still high even if other factors such as sleep hours, diet and exercise are controlled.
Although the study authors warned that they were unable to affirm the causal relationship between the two, they said that their findings increased the evidence supporting sleep in dark rooms.
Dale Sandler and Nong-Moon Park, co-authors of the National Institute of Environmental Health (NIEHS) in North Carolina, wrote: "The public health strategy to reduce obesity may have to be considered to reduce nighttime artificial light sources during sleep. Interventions."
They believe that the light may inhibit melatonin secretion, which in turn disrupts the physiological clock and eating habits.
Other possible roles for light play are "chronic stressors," which disrupt stress hormone secretion, such as glucocorticoids, which regulate food intake, or may have another mechanism that directly affects metabolism.
The study authors also acknowledged some limitations, including that the data was reported by the respondents themselves and they did not know the strength of the various light sources.
High levels of exposure to light may also "reflect a range of factors, including socioeconomic disadvantages and unhealthy lifestyles, which can also lead to weight gain and obesity."