Weather changes in the fall and spring can trigger migraine headaches, according to the American Migraine Foundation, which estimates that about 40 million Americans and 1 billion people worldwide live with this type of debilitating headache. Sensitivity to light, also known as photophobia, is one of the most common migraine symptoms. Now, Mayo Clinic researchers and collaborators report that both the brightness and color spectrum of indoor white light may affect how uncomfortable light feels for people with migraine.

Journalists: Broadcast-quality video of Dr. Todd Schwedt is in the downloads at the end of this post. Please courtesy: "Mayo Clinic News Network.

"During a migraine, exposure to normal lighting causes visual discomfort," says Dr. Todd Schwedt, a neurologist at Mayo Clinic in Arizona. "It also worsens the intensity of the migraine headache, often resulting in the need to retreat to a dark room."

In a study published in Sage Journals, researchers from Mayo Clinic and Arizona State University analyzed adults ages 18 to 45 who experienced episodic migraine, reporting four to 14 headache days per month and light sensitivity. Each participant completed two laboratory sessions, one while headache-free and another during an untreated migraine attack.

Participants were exposed to four types of white light enriched with different portions of the visible spectrum: green, blue, cyan and red. The light still appeared white, an important distinction from earlier studies that investigated visibly green light. During testing, researchers gradually increased the brightness. Participants rated their visual discomfort and researchers measured pupil size as an objective indicator of light sensitivity.

As expected, visual discomfort was worse during a migraine attack and with higher intensity light. Investigators also found that green-enriched white light was the most comfortable.

Other key findings:

• Green-enriched white light was associated with a 20% to 30% or greater reduction in visual discomfort compared with blue-enriched white light, depending on whether participants were experiencing a migraine attack.
• Green-enriched white light was associated with larger pupils and less discomfort, while blue and cyan-enriched light were associated with greater discomfort and smaller pupils.
• A second published study demonstrated a 37% reduction in visual discomfort with green-enriched white light and showed that, unlike other lighting, green-enriched white light does not worsen migraine headache intensity.

Researchers were able to develop a special type of white light enriched with green wavelengths that not only reduces visual discomfort and headache intensity but also improves thinking and concentration.

"Optimized lighting can provide more migraine-friendly environments in the workplace, schools, healthcare settings and in homes," says Dr. Schwedt, a co-author of the study. "Because the light still appears white, spectrally tuned lighting can be incorporated into these settings, even when they are shared by people with migraine and light sensitivity and those without."

Researchers are currently investigating potential benefits with longer exposure in real-world settings and whether changes in lighting improve headache severity and frequency and reduce disability.   

Dr. Schwedt is a co-founder of Allevalux, a company focused on lighting technology. For a complete list of authors, funding and disclosures, see the study.

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