You probably know that it’s hard to sleep with the lights on, but you may not be aware of the extent of your health that is affected by being exposed to light after dark. To the point that even a night light can have negative consequences.

            Firstly, light comes in many different forms (wavelengths). We see these differences in wavelengths as the different colors in the visible spectrum, ranging from red to violet. But, did you know that the different wavelengths of light have different effects on your brain? Some tell the brain to wake up and remain in an alert state, while others tell your brain to calm down and prepare for sleep. Why is this? Well, it turns out that sunlight, while being high in UV light (the wavelength of light beyond violet, that we can not see) it is also high in wavelengths of blue light. Special receptor cells in your eyes sense this blue light and pass it on to the part of your brain that regulates your sleep-wake cycle (or Circadian Rhythm) and tell your brain to stay alert. This is great when you’re trying to get work done during the day, but it can negatively affect your sleep schedule if you’re exposed to blue light around your bed time, or late into the night like so many of us are.

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            In fact, light is one of the most significant factors affecting your Circadian Rhythm. When there was no such thing as artificial light, or even up until we progressed beyond the incandescent bulb, the parts of the brain responsible for regulating the Circadian Rhythm were a lot healthier. Modern fluorescent, CFL, and LED bulbs emit light with a high percentage of blue wavelength light, constantly telling the brain that it needs to wake up. This is helpful for maintaining productivity at work or school, but can be dangerous around the times when the brain should be naturally producing more melatonin, and preparing for sleep (once the sun goes down). This is having lasting negative effects on cognition, short-term memory, metabolism, mood, and even immune function!

Sleep and Cognition/Memory

            Our sleep cycle is responsible for maintenance and recuperation of many different functions throughout the body. When we don’t sleep at the appropriate times, or have blue light exposure too close to our sleep, it can lead to our body resisting the natural flow through the sleep cycles of Slow Wave Sleep and Rapid Eye Movement Sleep. These are incredibly important, as they are how your brain stores memories, compiles newly learned tasks or abilities, and regulates multiple functions throughout the body. Also, lack of sleep makes it difficult for brain cells to communicate effectively, often leading to mental lapses that affect memory and visual perception. In fact, a study from Tel Aviv found that parts of the brain will actually exhibit behavior normally seen only when asleep, implying they were “dozing, causing mental lapses” during the day [3].

Sleep and Metabolism

            Another problem with this lack of proper sleep, is that it throws off your body’s hormone levels that are related to hunger and satiety. Being sleep deprived leads to too little leptin and too much ghrelin in your system. Leptin is the hormone that tells your brain when it’s full, and when to start burning more calories. Ghrelin, on the other hand is the hormone that tells your brain that you need to eat, when to stop consuming calories, and when to store calories as fat. Obviously, when these are out of sync, it can play havoc with your metabolism [5].

Sleep and Mood

            I think we’ve all come across a friend or loved one who exhibits behavior similar to a grumpy bear coming out of hibernation. Often, in our modern sleep deprived world, we can attribute this, not to a naturally grumpy disposition, but to a lack of proper sleep. It turns out that being a little out of sorts is the least of the issues related to mood and mental health. Lack of sleep can lead to much more severe issues such as anxiety, depression, or panic disorders.

Sleep and Immune Function

            Yes! Sleep even has an effect on your immune system. When you sleep, your immune system releases cells called cytokines. Certain cytokines are needed to increase when you have inflammation, an infection, or when you’re otherwise under stress [4]. Sleep deprivation decreases production of these cytokines, and can also reduce antibodies and immune cells in times when you’re under sleep deprivation [4].

Using Blue Light

It’s true, blue light does have it’s benefits. Utilizing it can be tricky though. Blue light increases alertness, cognition, and forces the brain to wake up. This makes it great for study, work, or staying awake when absolutely necessary (like in the case of shift workers). There is the downside to keep in mind though, that using blue light for long periods of time does decrease short-term memory. We' aren’t actually sure why this is, but a recent study out of PEC University of Technology showed that when exposed to blue light from LED screens, test subjects experienced a decrease in mood, attention-span, and memory performance [2].

How to Utilize the Power of Light

            Wow, light sure has a massive effect on the body. Let’s use what we know. How can we utilize our body’s close relationship with light to our advantage:

-Use bulbs that range on the side of the visible spectrum that is closer to red in the bedroom and bathroom.

-When working or studying, use LEDs and interact with your computer if possible.

-If you’ll be using a device with a screen for long periods of time over the course of the day, think of utilizing a blue light blocking device, such as computer glasses, or a blue light setting on your device.

-Avoid using devices or being exposed to blue light within 3 hours of bed time if at all possible (again utilize blue light blocking devices).

-Use devices with blue light for pleasure as little as possible (especially near bed time).

-Ensure that any lights used for night time visibility are close to the red end of the spectrum.


            Like everything in life, light utilization is a learning process. Pay attention to what works for you. Make conscious decisions in your light fixture usage, and where in your home they’re located. Do your own research on the fixtures or devices that you plan on using, as sometimes the device you’re using can be misleading. Do your best to stick to the 3 hours within bedtime rule, as it’s the most important to your overall health. I’m excited to implement these guidelines into my life and routine, and I hope you’ve found value in this as well.





1.       Health Impact of Light

2.       Light’s Effect on Cognition, Mood, and Circadian Rhythm

3.       What Happens if I Don’t Sleep Enough?

4.       Can Lack of Sleep Increase my Chances of Getting Sick?

5.       Sleep and Obesity

6.       Sleep and Mood Disorders