In the summer of 2019, I worked as an undergraduate research assistant in the CU Sleep and Development Lab where we studied how light exposure at night shifts circadian rhythm in pre-school aged children. There is a lot of research on the effects of light exposure in adults, but there is limited research on the effects in children. In adults, one study found that light exposure during the biological night, as short as 15-seconds, created significant phase delays (Rahman, et al., 2017). A phase delay means that a person secretes melatonin later than normal as a response to an environmental cue (light).
So, who cares, and why study this in children? Well, it is also known that circadian timing plays a very important role in almost all physiological functions, and a disturbance in circadian timing may lead to cognitive impairment, mood disturbances, and cardiometabolic disorders (Zee, Attarian, Videnovic, 2013). Further, it also known that children have distinct physiological differences compared to adults such as wider pupils and a clearer lens of the eye. This led us to believe that children would be more sensitive to light exposure. Thus, the birth of our lab. There is still a year left on the grant, but preliminary data we collected during the summer of 2019 suggests that pre-school aged children are extremely sensitive to light exposure. We were seeing phase delays in children at light intensities as low as 1 lux. For reference, the brightness of 1 lux is defined as the brightness of 1 candle from 1 meter away, so this is very dim.
Now, the main application of this research is related to the large amount of screen time we see today in children. Whether it is television, cell phones, or video games, screen time is a huge part of American culture. As healthcare providers, it is important that we are up to date with the most recent literature to provide the best advice to our patients (beneficence: do the most good for our patients). Parents need to be aware that there are health risks to screen time after bed, and now it is up to them if they desire to find another way to coax their kids to bed besides the highly effective method of screen time (autonomy: make their own decision for their kids after they are given all the information).
References
Rahman, S. A., St Hilaire, M. A., Chang, A. M., Santhi, N., Duffy, J. F., Kronauer, R. E., Czeisler, C. A., Lockley, S. W., & Klerman, E. B. (2017). Circadian phase resetting by a single short-duration light exposure. JCI insight, 2(7), e89494. https://doi.org/10.1172/jci.insight.89494
Zee, P. C., Attarian, H., & Videnovic, A. (2013). Circadian rhythm abnormalities. Continuum (Minneapolis, Minn.), 19(1 Sleep Disorders), 132–147. https://doi.org/10.1212/01.CON.0000427209.21177.aa
This is a very interesting field of study, especially given the prevalence of electronics in most peoples lives and bedrooms. Most people have electronic clocks, TVs that give off light even when off, or other electronics that have some low level lighting that is a constant. While it may be more difficult to measure these exact levels as they vary, it would be interesting to see if they accounted for a singular lux, as this was the amount used as a threshold for circadian rhythm change. However, I must disagree with the idea that a single lux is not a lot of light, knowing full well this is an individual opinion. A fully lit candle from three feet away is enough to read by (depending on the size of said candle of course). Also, a full moon gives off 0.108 lux, which I know is often enough light to make it difficult for myself to sleep. Given this metric will be incredibly individualized, but I am not surprised that 1 lux is enough to cause sleeping issues.
ReplyDeleteWhile many of these sleep studies are done on adults as you said, it is interesting to me that as an adult there has not been more education as to keeping lower levels of light in bedrooms. Disrupting the circadian system of individuals can lead to chronodisruption, which has been associated with incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging, and some types of cancer (Bonmati-Carrion et al., 2014). This knowledge encourages me to never fall asleep with the TV on, as many people are prone to do.
Bonmati-Carrion, M. A., Arguelles-Prieto, R., Martinez-Madrid, M. J., Reiter, R., Hardeland, R., Rol, M. A., & Madrid, J. A. (2014). Protecting the melatonin rhythm through circadian healthy light exposure. International journal of molecular sciences, 15(12), 23448–23500. https://doi.org/10.3390/ijms151223448
Sleep in children is very important. Recommended sleep duration for children that are 3 to 5 years is at least 10 to 13 hours. Light suppresses melatonin in humans. The strongest response is light that has wavelengths between 446-477nm, which is blue light. A study exposed eight subjects to blue LED light, and showed increased melatonin suppression. (West, K., Jablonski, M., et al, 2009). Melatonin is the hormone of darkness and plays a strong role in circadian rhythms.
ReplyDeleteI think it would be best to educate parents about how blue light can keep their child up at night and to implement "no screen-time" hours before bed time. I think this would help children get those long hours of sleep, which will aid in their development!
References
West, K. E., Jablonski, M. R., Warfield, B., Cecil, K. S., James, M., Ayers, M. A., Maida, J., Bowen, C., Sliney, D. H., Rollag, M. D., Hanifin, J. P., & Brainard, G. C. (2011). Blue light from light-emitting diodes elicits a dose-dependent suppression of melatonin in humans. Journal of applied physiology (Bethesda, Md. : 1985), 110(3), 619–626. https://doi.org/10.1152/japplphysiol.01413.2009
This is a very interesting topic! In addition to screen time, so many children have night lights, clocks, even televisions in their rooms that give off light. I found a study (Akacem et. al 2018) examining light induced melatonin supression in preschool aged children that suggests that children are actually more suseptible to sleep disturbances caused by light, compared to adults.
ReplyDeleteI would also be interested to see more studies regarding light disturbances in children who are still napping, as they have a more abnormal circadian rhythm, and light sources can be significantly more difficult to control during the daytime.
Akacem, L. D., C. T. Simpkin, M. A. Carskadon, K. P. Jr Wright, O. G. Jenni, P. Achermann, et al. 2015. The timing of the circadian clock and sleep differ between napping and non‐napping toddlers. PLoS ONE 10:e0125181.