Why Do We Hate Light? Perhaps the Answer is More Complicated Than We Thought

One of my earliest memories was sitting in a swing at preschool. I would not know for years that migraine was the cause, but my head hurt so bad I could barely see. There was no shade to be found, and I could not escape the summer sun. It was pounding down on my head and I had nothing to shield my eyes except my small hands.

A funny fact about my preschool was that it was practically infested with grasshoppers. I was afraid that all the little grasshoppers surrounding me had headaches and felt as sick as I did. I began to pick up each grasshopper one by one and hide them in the shade under the preschool porch where they would be protected from the sunlight. Forty years later I still remember this misery as clear as day.

“At least 40% of us have photophobia to some extent…”

Why are we as a community of people with migraine so averse to light? At least 40% of us have photophobia to some extent, but none of us really understand it. A few pioneering scientists have set out to determine what it is about light that bothers us so much. Are there certain types of light or wavelengths of light that are worse than others?

The historical consensus seems to have been that blocking blue light is what is best for us. There are all sorts of gadgets available out there to protect us from “blue light”.  We can find glasses, screen covers, and filter apps to protect us from the evils of blue light. There has also been some indication that green light might be soothing or help protect us from our pain. For the most part, we learned this information through experimental studies, carried out either in animals or in a rather controlled setting very unlike the circumstances of our every day lives.

One of the interesting things about science is that we need to replicate data in different settings using different methods in order to discover the truth. Recently, Dr. Suzanne Bertisch, MD, MPH from the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital probed the issue of light and migraine from a slightly different angle. The hypotheses of this study were similar to the findings of previous studies: that migraines would be more likely to occur following exposure to higher than average brightness and high exposure to ratio of blue to green light would also be associated with migraine. Her data shows us that perhaps the answers are not as simple as we may have thought.

Don’t worry, this is not unusual in science. Science often progresses from animal models to human data that is in the experimental setting or is retrospective (meaning looking back or recalling past events). Then it progresses to studies that look at the problem in a prospective manner where people are followed over time, or possibly utilizing methodology that may be able to mimic more real-life conditions.

Dr. Bertisch studied 79 individuals with episodic migraine over a six week time period. The study utilized a method call actigraphy to measure each person’s light exposure from a device on their wrist. Actigraphy is a method that is traditionally used to monitor rest and activity cycles, but can also be used to monitor light exposure. Headache data including timing, duration, intensity, and associated symptoms were recorded in a headache diary. Other important information like menstrual status, dietary, and exercise factors were also tracked.

“It also makes us question whether we are optimally blocking light with some of our blue light blocking devices.

It is no surprise that the data from this study indicated that higher than average intensity of white light is associated with the onset of migraine. This is after taking into consideration other important factors like age, sex, genetics, diet, exercise, stress, etc. What was surprising was that utilizing this method that studied light in a more naturalistic setting, exposure to a higher ratio of blue light relative to green light was associated with lower maximal pain intensity. This finding was not only opposite to what the authors were expecting to find, but it contrasts previous findings carried out in experimental settings that suggest that green light may lower pain intensity. It also makes us question whether we are optimally blocking light with some of our blue light blocking devices. Is there room for improvement?

I contacted Dr. Bertisch to comment on her findings and her thoughts were that her research did not necessarily contradict previous work because her recent work was the first to look at light in the “naturalistic setting”.  The manner in which her study “captured light was very different than most experimental studies”. Previous work looked at very specific wavelengths, and the broad spectrum studied in the most recent work was key. She will be publishing the latest study soon so that other labs may try to replicate it and we can get to the bottom of why light triggers our migraine attacks.

What I like about this data is that it indicates there may be more to learn about the light that triggers our migraine attacks, and possibly our glasses and devices that we use to protect our eyes. We could have another opportunity ahead of us to improve the tools we use in our battle against migraine. This makes this topic exciting to me and should give us all hope for a brighter (or more appropriately, less bright) future.

Bertisch S., Shedding Light on Migraine: Exploring Novel Light Metrics as a Trigger of Migraine https://migraineresearchfoundation.org/researchers/suzanne-bertisch/

Noseda R, Berein CA, Nir RR et al. Migraine photophobia originating in cone-driven retinal pathways. Brain 2016 Jul; 139(Pt 7):1971-86.

Bernstein CA, Nir RR, Noseda R et al. The migraine eye: distinct rod-driven retinal pathways’ response to dim light challenges the visual cortex hyperexcitability theory. Pain. 2019 Mar; 160(3):569-578.

Originally Published on February 28, 2020 at the Association of Migraine Disorders: https://www.migrainedisorders.org/migraine-light-sensitivity/