Light exposure during sleep can have a negative impact on health

New research has revealed that even a moderate amount of ambient light during nighttime sleep can harm cardiovascular function and increase insulin resistance the following morning. This can increase risk for heart disease, diabetes, and metabolic syndrome.

The study, published in the journal, Proceedings of the National Academy of Sciences, was conducted by researchers at Northwestern University in Evanston, Illinois.

Researchers evaluated 20 young adults and found one night of moderate (100 lx) light exposure during sleep increases nighttime heart rate, decreases heart rate variability, and increases next morning insulin resistance when compared to a simply lit (less than 3 lx) environment. In addition, they found a positive relationship between higher sympathovagal balance and insulin levels, suggesting that sympathetic activation may play a role in the observed light-induced changes in insulin sensitivity.

The study also found that obesity was highest in participants who reported sleeping with a television or light on in the bedroom, suggesting that light in the bedroom during nighttime sleep may negatively influence metabolic regulation.

“In addition to sleep, nutrition and exercise, light exposure during the daytime is an important factor for health, but during the night we show that even modest intensity of light can impair measures of heart and endocrine health,” said co-first author Ivy Mason, PhD, a former post-doctoral fellow at Northwestern.

Integrative practitioners can keep this in mind when talking with their patients about sleep hygiene routines.