The association between ambient air pollution and migraine: a systematic review

Some studies have shown the effect of air pollution on migraine. However, it needs to be confirmed in larger-scale studies, as scientific evidence is scarce regarding the association between air pollution and migraine. Therefore, this systematic review aims to determine whether there are associations between outdoor air pollution and migraine. A literature search was performed in Scopus, Medline (via PubMed), EMBASE, and Web of Science. A manual search for resources and related references was also conducted to complete the search. All observational studies investigating the association between ambient air pollution and migraine, with inclusion criteria, were entered into the review. Fourteen out of 1417 identified articles met the inclusion criteria and entered the study. Among the gaseous air pollutants, there was a correlation between exposure to nitrogen dioxide (NO₂) (78.3% of detrimental relationships) and carbon monoxide (CO) (68.0% of detrimental relationships) and migraine, but no apparent correlation has been found for sulfur dioxide (SO₂) (21.2% of detrimental relationships) and ozone (O₃) (55.2% of detrimental relationships). In the case of particulate air pollutants, particulate matter with a diameter of 10 μm or less (PM₁₀) (76.0% of detrimental relationships) and particulate matter with a diameter of 2.5 μm or less (PM_2.5) (61.3% of detrimental relationships) had relationships with migraine. In conclusion, exposure to NO₂, CO, PM₁₀, and PM_2.5 is associated with migraine headaches, while no conclusive evidence was found to confirm the correlation between O₃ and SO₂ with migraine. Further studies with precise methodology are recommended in different cities around the world for all pollutants with an emphasis on O₃ and SO₂.