Artificial light at night may affect your heart health. According to a recent study, artificial light at night is associated with a higher prevalence of obesity, diabetes, and hypertension. The study sampled older adults (aged 63-84). Participants were exposed to artificial light at night and provided an activity wrist monitor to collect data on exposure to light over a seven-day period. Participants who were exposed to light at night had shorter sleep times and time in bed, lower sleep efficiency, and later sleep onset compared to those with no exposure to light at night. Another study measured insulin resistance in the morning following two nights of exposure to either dim or overhead lighting during sleep. Participants were placed into two groups. One group was exposed to dim light during the first night of sleep and then room light on the second night of sleep. The other group was exposed to dim light during sleep for two nights in a row. The study included 20 young adults and found that insulin resistance was higher among those exposed to room light than dim light. Participants from the overhead light group also had higher heart rates and lower heart rate variability.
Circadian rhythms are the changes in your body occurring during a 24-hour cycle as a result of day and night cycles in our environment. Circadian rhythms impact the release of hormones, digestion, cell regrowth, body temperature, blood pressure, and heart rate. If someone has ever flown cross country, they've probably noticed it’s difficult to wake and sleep in a time zone several hours different from their home environment; this is because their body has adapted to waking up and falling asleep during a set time. It can take several days for the body to adjust to the time change. Artificial light can adjust this rhythm. It's also used around the home for other purposes: to cook, clean, shower, watch TV, read a book, or prevent one from tripping and falling over floor items which are seen better during the day. However, the studies mentioned above show that there may be some health risks to exposure to artificial light at night.
Sunlight
Not all light is bad. Sunlight helps the body produce vitamin D, which is good for maintaining healthy bones and helps the body absorb calcium. Additionally, scientists believe that time in the sun may shrink fat cells below the skin, and aid in eye health. If you’re an early riser, early morning sunlight may help you get to sleep faster at night.
Alternatives to night lights
Artificial night lights may increase productivity for some; still, your sleep and heart health are important. Consider reducing your exposure to artificial light at night as much as possible. Researchers recommend avoiding using electronic devices while in bed at night, as some devices expose the body to blue light, tricking the body into thinking this blue light represents daylight, potentially causing an interruption in sleep. If you have to use your electronics in bed at night, consider a blue light filter for the device. For older adults worried about tripping over objects at night, researchers recommend warm-colored night lights, like red or amber-colored lights.
References
Crnko, S., Du Pré, B. C., Sluijter, J. P., & Van Laake, L. W. (2019). Circadian rhythms and the molecular clock in cardiovascular biology and disease. Nature Reviews Cardiology, 16(7), 437-447.
Kim, M., Vu, T. H., Maas, M. B., Braun, R. I., Wolf, M. S., Roenneberg, T., ... & Zee, P. C. (2022). Light at night in older age is associated with obesity, diabetes, and hypertension. Sleep.
Mason, I. C., Grimaldi, D., Reid, K. J., Warlick, C. D., Malkani, R. G., Abbott, S. M., & Zee, P. C. (2022). Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences, 119(12), e2113290119.
National Heart, Lung, and Blood Institute. (2022). Turn off all the lights at night: Your heart will thank you. Retrieved from: https://www.nhlbi.nih.gov/news/2022/turn-off-lights-at-night-your-heart-will-thank-you
National Institute f General Medical Sciences. (2022). Circadian rhythms. Retrieved from: https://www.nigms.nih.gov/education/fact-sheets/Pages/Circadian-Rhythms.aspx
Rumanova, V. S., Okuliarova, M., & Zeman, M. (2020). Differential effects of constant light and dim light at night on the circadian control of metabolism and behavior. International Journal of Molecular Sciences, 21(15), 5478.
WebMD. (2022). Sunlight and your health. Retrieved from: https://www.webmd.com/a-to-z-guides/ss/slideshow-sunlight-health-effects
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