Have a headache and don't know why? It could be high levels of air pollution.

A study from the densely populated Santiago Province of Chile -- a region surrounded by the Coastal and Andes mountains and, therefore, geographically prone to air pollution - found increased hospital admissions for migraines and other headaches on days of elevated air pollution readings.

Further investigations are needed to confirm the consistency of these findings in different regions, Dr. Sabit Cakmak, with Health Canada in Ottawa, Ontario, and co-investigators say.

In the study, reported in the American Journal of Epidemiology, Cakmak's team assessed air pollution levels taken at 7 monitoring stations between 2001 and 2005. The stations measured for ozone and air pollutants such as nitrogen and sulfur dioxide, carbon monoxide, and tiny, floating particles known as particulate matter associated with the combustion of gasoline, natural gas, and other fossil fuels.

During the same period, the investigators collected information on the number of hospitalizations for migraine headache, as well as tension, cluster, or other types of headache.

When the investigators pooled the air pollution data from all regions they found, air pollution was a risk factor for all types of headache. This remained true in all pollutant-headache combinations analyzed.

These associations did not significantly change in analyses that accounted for the influence of age, gender, or season, Cakmak noted.

Based on their findings, Cakmak and colleagues say the estimates of the burden of illness and costs associated with poor air quality should include illness associated with headache.

SOURCE: American Journal of Epidemiology, October 15, 2009