By now, most of us know that increased exposure to light at night can affect our sleep, memory, and concentration. [1] However, recent studies show that being exposed to light at night can raise the risk of having diabetes. According to a study by Daniel Windred and his team, exposure to personal light at night can increase the risk of type 2 diabetes.
A few previous studies have shown that exposure to night light increases the risk of diabetes, obesity, and hypertension. [2,3] These studies show a weaker association between exposure and effect. However, a more recent study was conducted in a larger population, focusing on personal indoor exposure to light at night. This study found that increased exposure to personal indoor lighting at night, where people spend 80% of their time, can make them prone to type 2 diabetes.
This is important to know now because this is a modifiable risk factor that is on the rise along with the diabetic surge today. So, we'll talk about the basic physiology of our bodies, how light at night affects them, what recent research has revealed, and some preventative measures.
Our body has a circadian system that regulates the timing of our bodily processes and behavior daily. This is called the circadian rhythm. A central pacemaker monitors this rhythm in an organ called the hypothalamus. The key role of this pacemaker is to align our internal systems and processes according to the external phases of our day and behavior. [4] This mainly involves hormonal shifts, like inducing a peak in insulin secretion during the day and a peak in glucose secretion at night.
It is also known that several environmental or genetic changes can influence this rhythm. The natural light/dark cycle (of the sun) is a primary signal for our circadian rhythm. This natural signal has changed with the advent of artificial light at night and shift work. Excessive light exposure at night delays or advances the internal 24-hour phase, confusing our body’s systems. [5] Constant disruption of this rhythm can affect your hormones, mood, and metabolism. [4]
Thus, a disrupted circadian rhythm can lead to inadequate sleep. This, in turn, sets fire to a circuit of health issues in your body. But here we will be discussing the risk of diabetes. Though sleep disruption in itself can raise diabetes risk, recent studies show an independent connection between night light and diabetes.
There are a few previous studies that have found this association between nighttime light and diabetes risk. [6] But the limitations of all these studies can be put together into the following points:
They mostly focus on night shift workers, including both outdoor and indoor exposure to light at night.
Personal light exposure was studied in a small number of people.
Studies were done on animal models.
The most recent study by Daniel Windred and his team surpassed these limitations. They focus their research on exposure to personal indoor light at night, which is where people spend 80% of their time. They collected a larger study population of 85,000 people. Their daytime light exposure from 7:30 AM to 8:30 PM and nighttime light exposure from 12:30 AM to 6:00 AM were collected using wrist-worn light sensors for one week. Using this, the variation in the phase and amplitude of their circadian rhythm was calculated.
All these patients were followed up for 8 years to determine the incidence of type 2 diabetes. After excluding other causative and genetic factors, an independent relationship between exposure to personal light at night and diabetes was found.
The rationale: The disrupted circadian rhythm causes melatonin and glucocorticoids, the two substances that maintain circadian rhythm, to elevate. When these substances increase in the body, they suppress insulin secretion and stimulate glucose production from the liver at times that coincide with food intake. This misalignment, when persistent, can cause inflammation, insulin resistance, and type 2 diabetes. [6]
Poor sleep
Cognitive disturbances, like poor memory and concentration, lead to accidents.
Mental health disorders like anxiety and depression due to sleep disruption.
Higher incidence of metabolic syndrome, and cardiovascular diseases.
Increased risk of breast cancer in women. This is linked to dysregulated melatonin secretion, which has anti-cancer properties. [7]
New findings from our group, published in The Lancet Regional Health – Europe. Light exposure at night is a robust predictor of incident type 2 diabetes. Modeling indicates that circadian disruption is a likely culprit. Reducing night light exposure might help to mitigate the risk of type 2 diabetes, even in people with high genetic susceptibility.
Daniel Windred, Sleep and Circadian Rhythm Researcher, Monash University
Steps to minimize the risks caused by exposure to light at night include reducing the exposure first, optimizing your habits, and maintaining good sleep hygiene.
Start your day bright: Exposure to bright light within the first two hours of waking up can set the tone for better sleep at night. This is because earlier exposure to daylight can advance your circadian rhythm. This means that you will get the cue to sleep at the right time for your body and will sleep better. Many blame their insomnia on screen addiction, while the latter can be the culprit that worsens their insomnia.
Set a no-screen time: Excessive use of the screen before bed has been the main cause of exposure to light at night. Set a time to switch off all the gadgets at least 2 hours before going to bed. 2 hours is the sweet spot because, this time, you are more prone to phase (sleep) delay.
Dim lights or pitch dark: We commonly use LED lights today. But they are major emitters of blue light, the type known to suppress melatonin production. Switch off any bright white lights and use dimmer lights if needed. It is always best to sleep in a pitch-dark room, as now your eyes have nothing to do except be shut for sleep.
Use screens wisely: Let's be honest. Today we need to sit in front of screens for work. Using screens has become mandatory, more than just for pleasure. So use it wisely to protect your rhythm. Put your gadgets in night mode, dim the brightness, or use blue light filters, as suggested by experts. There are even apps like Redshift and Darkreader that can adjust your screen's color temperature and light mode.
It is okay to nap: We know daytime naps can lead to obesity and cardiovascular diseases. But that is less likely if your nap is shorter than 30 minutes. [10] Having a short nap during the day is important to reduce sleep pressure. Sleep pressure builds up when you prolong your sleep time since waking up. This can lead to fatigue, further disrupting your circadian rhythm and night sleep. Hence, a short nap of not more than 30 minutes can prevent this.
Mind your dinner: What you eat and when you eat dinner matter. Eating heavy meals late at night can disrupt your circadian rhythm. Experts advise having your dinner 2 to 4 hours before bedtime. Avoid a heavy dinner close to bedtime. So that your sleep isn’t affected and you aren’t tempted to switch on the lights or pick up your phones. Also, this can stabilize your glucose levels before sleep. But if you are hungry, it is okay to take a light, healthy bedtime snack. [9]
Consistent bedtime routine: To help the body maintain its circadian rhythm, try to go to bed and wake up every day at the same time, even on holidays.
For the shift workers: Taking care of your natural rhythm is not easy for shift workers. Some actions that they can take are:
Prioritize sleep over other work post their shift. Sleep as long as possible.
Take advantage of the breaks they get during the shift to have a short nap.
Do not over-commit with unnecessary work, both at home and at work.
If you are on a night shift, try to avoid bright light exposure in the second half of the night so that it is easier to sleep as soon as you get home.
Always have a prepared environment with minimal light and distractions to sleep.
Employers and organizations also play a huge role in maintaining the work-life balance of night-shift workers.
Other lifestyle shifts: There are a few lifestyle recommendations that ensure that your circadian rhythm is regulated. They are:
Avoid caffeine 5 hours before the planned sleep time.
Exercise can regulate your system. But avoid doing it 3 hours before sleep.
Avoid alcohol.
Get your insomnia treated soon. Approach a healthcare provider to seek help.
Exposure to light at night disrupts circadian rhythms and can increase the risk of type 2 diabetes, as found in a study by Daniel Windred and his team. This study, involving 85,000 participants, showed that greater indoor light exposure at night correlates with a 67% higher risk of developing diabetes due to hormonal imbalances affecting insulin and glucose levels. To mitigate these risks, individuals should minimize night-time light exposure, maintain good sleep hygiene, and adopt consistent sleep routines, while shift workers need to prioritize sleep and manage their light exposure carefully.
References:
Mushfiqul Anwar Siraji et al., “Light exposure behaviors predict mood, memory,and sleep quality,” Scientific Reports 13, no. 1 (August 1, 2023), https://doi.org/10.1038/s41598-023-39636-y. (Cited on 26/07/2024)
Kim, Minjee, Thanh-Huyen Vu, Matthew B. Maas, Rosemary I. Braun, Michael S. Wolf, Till Roenneberg, Martha L. Daviglus, Kathryn J. Reid, and Phyllis C. Zee. "Light at night in older age is associated with obesity, diabetes, and hypertension." Sleep 46, no. 3 (2023): zsac130. (Cited on 26/07/2024)
Obayashi, Kenji, Yuki Yamagami, Norio Kurumatani, and Keigo Saeki. "Bedroom lighting environment and incident diabetes mellitus: a longitudinal study of the HEIJO-KYO cohort." Sleep medicine 65 (2020): 1-3. (Cited on 26/07/2024)
Vetter, Céline. "Circadian disruption: What do we actually mean?." European Journal of Neuroscience 51, no. 1 (2020): 531-550. (Cited on 26/07/2024)
National Toxicology Program. NTP Cancer Hazard Assessment Report on Night Shift Work and Light at Night. Research Triangle Park (NC): National Toxicology Program; 2021 Apr. 1, Circadian Regulation and Disruption, Night Shift, and Light at Night: Characterization and Exposure. Available from: https://www.ncbi.nlm.nih.gov/books/NBK571591/ (Cited on 26/07/2024)
Windred, Daniel P., Angus C. Burns, Martin K. Rutter, Chris Ho Ching Yeung, Jacqueline M. Lane, Qian Xiao, Richa Saxena, Sean W. Cain, and Andrew J.K. Phillips. “Personal light exposure patterns and incidence of type 2 diabetes: analysis of 13 million hours of light sensor data and 670,000 person-years of prospective observation.” the Lancet Regional Health. Europe, June 1, 2024, 100943. https://doi.org/10.1016/j.lanepe.2024.100943. (Cited on 26/07/2024)
Davis, L. K., Bumgarner, J. R., Nelson, R. J., & Fonken, L. K. (2023). Health Effects of Disrupted Circadian Rhythms by Artificial Light at Night. Policy Insights from the Behavioral and Brain Sciences, 10(2), 229-236. https://doi.org/10.1177/23727322231193967 (Cited on 26/07/2024)
Blume, Christine, Corrado Garbazza, and Manuel Spitschan. “Auswirkungen von Licht auf zirkadiane Rhythmen, Schlaf und die Stimmung bei Menschen.” Somnologie 23, no. 3 (August 20, 2019): 147–56. https://doi.org/10.1007/s11818-019-00215-x. (Cited on 26/07/2024)
https://www.sleepfoundation.org/nutrition/is-it-bad-to-eat-before-bed (Cited on 26/07/2024)
Vizmanos, Barbara, Ana Isabel Cascales, María Rodríguez‐Martín, Diego Salmerón, Eva Morales, Aurora Aragón‐Alonso, Frank a. J. L. Scheer, and Marta Garaulet. “Lifestyle mediators of associations among siestas, obesity, and metabolic health.” Obesity 31, no. 5 (April 26, 2023): 1227–39. https://doi.org/10.1002/oby.23765. (Cited on 26/07/2024)
https://www.cdc.gov/niosh/work-hour-training-for-nurses/part2.html (Cited on 26/07/2024)
