Temperatures are rising across parts of the United States, bringing a record-setting early heat wave with it. While staying cool is the immediate priority, a new study in the journal Neurology suggests another risk factor should be on your radar: a higher-than-usual likelihood of migraine headaches during the late spring and summer months. The research followed 7,032 people with migraines in Israel for a decade, tracking their daily exposure to air pollution and weather conditions to identify links between environmental factors and headache frequency.
During the study period, 2,215 participants—about 32%—visited a hospital or clinic for migraine at least once. Researchers compared these visits to pollution and weather levels on the day of the event and the seven days prior. They found a correlation between specific weather patterns and an increased number of clinic visits.
Higher levels of air pollution were associated with the most migraine-related hospital visits. People with short-term exposure to high levels of nitrogen dioxide, a common traffic exhaust pollutant, were 41% more likely to seek care for a migraine than those with lower exposure. The study also identified a link between UV ray exposure and healthcare visits, finding that people exposed to high levels of sunlight were 23% more likely to visit a provider for migraine symptoms. High temperatures combined with low humidity appeared to amplify the effect of nitrogen dioxide, increasing the risk of headaches.
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The study didn’t prove that pollution and heat cause migraines, only that they are linked. However, experts say the connection makes biological sense. Nitrogen dioxide and other particulates can spark neuroinflammation, an immune response in the brain that may release pain chemicals like calcitonin gene-related peptide (CGRP) and substance P. This inflammation can irritate nerve endings, particularly for people who also suffer from allergies, whose bodies may treat pollution as an allergen and mount a similar immune response.
Heat itself impacts blood vessels and nerves. When the body heats up, blood vessels and nerves in tight spaces can expand, causing irritation. This dilation can trigger pain signals. High humidity, which is common in spring and summer, presents a different problem. It causes sweating and fluid loss, which can decrease blood volume and constrict blood vessels. That sudden narrowing of vessels, combined with dehydration, can lead to headaches just as effectively as dilation.
Doctors often recommend keeping a headache diary to track triggers, but avoiding pollution and humidity can be difficult. If pollution levels are high, wearing an N95 mask outdoors and running an air purifier indoors may help. When heat and humidity strike, staying hydrated with water and electrolytes is critical to maintaining blood vessel function.
