When to Use Blue Light Blocking Glasses? (How Early At Night?)

At this point, you’ve probably started learning about sleep hygiene, which includes limiting exposure to blue light at night as it can cause insomnia symptoms.

Once you have a good pair of blue light glasses, the question becomes how best to utilize them.

I’m going to summarize research and other information on this topic, but if you’re really in a rush, the short answer is that blue light glasses should be worn at least an hour before going to sleep.

How Soon to Wear Blue Light Blocking Glasses Before Sleeping?

The whole reason that blue light is a problem for sleep quality is that it suppresses melatonin production.

The degree of suppression depends on the duration and intensity of the blue light source. In other words, a blindingly bright huge TV screen will suppress melatonin more than a dim phone screen at night.

One study looked at the effect of 30 minute periods of looking at a “normal” computer monitor at night. They found (1):

A white light source with more short-wavelength content than an incandescent light source would result in nearly 20% suppression, which is close to the suppression levels obtained in this study

That’s honestly not that bad. But you do need to consider other LED light sources in your environment that may add to the suppression.

How Long Does it Take For Melatonin Levels to Rise?

Let’s say you’re simply using your laptop at a reasonable brightness at night.

Combined with any sources, your melatonin would be suppressed by 20% or maybe a bit more. We need to know how long it takes for melatonin levels to return to a “normal” level that’s high enough to get to sleep.

The good news is that melatonin levels rise very fast at night once you’re not exposed to significant amounts of blue light.

The graph below shows the period of “darkness” with a gray line under the curves (2). As soon as it is “dark”, melatonin levels more than triple within 2 hours.

We can be safe and say that melatonin levels will return to “normal” within an hour once blue light is minimized for most individuals.

A study looked at the effect of melatonin supplements during the day, which isn’t exactly what we’re concerned with, but still shows how fast melatonin levels can respond (3).

Within an hour, melatonin levels had risen significantly even at very low doses of melatonin (you really don’t need to take much melatonin if you ever want to try it).

SummaryAs long as blue light is minimized for at least an hour before trying to sleep, melatonin levels should be close to “normal.” Therefore, it’s typically best to wear blue light blocking glasses at least an hour before bedtime, but even right after sunset could be beneficial.

Is Blue Light Dangerous?

The obvious follow-up question is if there are benefits to wearing blue light blocking glasses for even longer periods.

Aside from staring into the sun or at welding arcs, the intensity of blue light from other sources like screens is too low to pose any danger (4).

One study found that blue light emitting diodes are safe to look at for long periods of time (5):

The hazard analysis found that the blue LED panel was safe for 8 h of continuous exposure, even for photosensitive individuals

So blue light is not an enemy that needs to be avoided all the time without a good reason.

Eye strain is the more serious concern from using screens, but that has more to do with brightness, extended periods of use, and other habits (6).

Should You Wear Blue Light Glasses During the Day?

There are blue light glasses with clear lenses that block about 25% of blue light frequencies.

While these can be worn during the day, it won’t have a significant effect on sleep either way.

Wearing stronger blue light glasses during the day could actually be a negative thing. Your circadian rhythm relies on exposure to light frequencies like blue light to regulate many complex processes in your body.

Blocking blue light during the day can affect energy levels, mood, and more.

SummaryUnless you have a good reason to, most people shouldn’t wear blue light glasses during the day time.

Should You Wear Blue Light Glasses While Driving?

You’re exposed to quite a bit of blue light from LED headlights and streetlights when driving at night.

So if you sleep right after driving home, the blue light can make it harder to get to sleep.

Unfortunately, orange tinted blue light glasses can be dangerous to drive with, because they block out too much light and can impair visibility. You also wouldn’t want to become too sleepy while driving.

A middle ground that many people go is to use yellow-tinted blue light glasses, which block around 50-60% of blue light.

As we saw before, the degree of melatonin suppression depends on the overall exposure to blue light, so even reducing it by this amount can improve sleep quality.

References

1. The impact of light from computer monitors on melatonin levels in college students
2. Melatonin the "light of night" in human biology and adolescent idiopathic scoliosis
3. Effect of inducing nocturnal serum melatonin concentrations in daytime on sleep, mood, body temperature, and performance.
4. Evaluation of blue-light hazards from various light sources
5. Blue light from light-emitting diodes elicits a dose-dependent suppression of melatonin in humans
6. Digital eye strain: prevalence, measurement and amelioration