The population seems almost split in the middle when it comes to sleeping in absolute darkness or keeping a dim source of light on when going to bed. In some cases, night lamps or night lights may not just be beneficial, but almost necessary, like in the case of people with night blindness or the elderly to avoid the risk of falling or bumping into sharp corners.
However, preferring a night light goes beyond these medical obligations and into the realm of preference. If you are one of those, I have some bad news for you. According to a study published by The Lancet, keeping a light on when going to sleep can increase your risk of diabetes.
Understanding The Circadian Rhythm
Despite mankind’s advancement since our ancestors lifted their paws from the ground and started walking upright, there is a lot that we still share with our forefathers. One of these crucial inheritances is the circadian rhythm. You see, Thomas Edison invented the light bulb not even 200 years ago. For millions of years before that, we used to wake up with the light of the sun, and go to sleep once it got dark outside.
Our body’s processes also conditioned themselves to work in tune with this routine. For millions of years, our bodies’ physiological processes like hormone secretion or metabolism, have been conditioned to act this way. So when you keep the light on at night, when ideally your body has an evolutionary body clock that requires darkness while sleeping, your physiological processes get disturbed.
How Light Influences Our Biological Day and Night
The circadian rhythm is a fundamental timekeeper for our bodies. Here are some processes that are impacted by the internal body clock:
- When light reaches our retina, it sends action potentials through the optical nerves to the region of our brain that houses the master clock that coordinates both the peripheral and central nervous systems.
- When we wake up and are exposed to light, it can trigger a significant temporary increase in serum cortisol levels, known as the cortisol awakening response, which signals our body that the day has started.
- On the flip side, as daylight fades at sunset, the secretion of melatonin from the pineal gland increases, indicating the onset of the biological night.
How Does Night Light Cause Diabetes?
The Lancet study has found that artificial light during the evening and night can interfere with these natural processes. This disruption can suppress melatonin secretion and is associated with increased risks of conditions like obesity, type 2 diabetes, and hypertension, especially with prolonged exposure to light at night.
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The researchers analysed data from the UK Biobank cohort, examining approximately 13 million hours of light sensor data from 84,790 participants who wore light sensors for a week. The study found a positive correlation between nighttime light exposure and the risk of developing type 2 diabetes over an average follow-up period of 7.9 years.
People who were exposed to the most nighttime light (top 10%) had a higher risk of getting type 2 diabetes compared to those who were exposed to the least nighttime light (bottom 50%). This increased risk was still significant even when genetic factors were considered. Additionally, those whose light exposure was similar during the day and night, and those with irregular daily light patterns, also had a higher risk of developing type 2 diabetes.
Should You Switch The Light Off When Going To Bed?
The Lancet study suggest that reducing nighttime light exposure, increasing daylight exposure, and maintaining regular light exposure patterns could be effective strategies to lower the risk of type 2 diabetes. However, these findings can not be generalised. This is because each one of us is not equally sensitive to light. Plus, the study has yet to consider factors like the effect of blue-light-blocking glasses, sleep masks, or midnight snacking.
Moreover, despite its potential health risks, nighttime light does serve important functions, such as facilitating work in healthcare settings, improving indoor visibility, and providing a sense of safety.
So what’s the takeaway? Should you or should you not switch the lights off when going to bed? It might seem inconclusive, but the simple answer is that it is up to you. Research like this one by The Lancet serves to increase your understanding to help you make informed decisions. So you decide how you want to enhance your well-being and potentially reduce the risk of chronic conditions like type 2 diabetes. Promoting better light hygiene might just be an easy and effective step towards a healthier life. It is not too much to give up in the quest for better health!
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