PhD Student Western University London, Ontario, Canada
Rationale: Among many others, known triggers for seizures include stress, alcohol consumption, and sleep deprivation. However, not all seizures can be predicted or prevented, indicating the existence of seizure triggers that have not yet been identified. Published research examining outdoor air pollution as a potential seizure trigger has been accumulating in recent years. Our objective was to systematically review the available evidence examining the association between outdoor air pollution exposure and the risk of seizures. Methods: MEDLINE, EMBASE, SCOPUS, Web of Science, BIOSIS Previews, Proquest Theses and Dissertations, the grey literature, and select conference proceedings were searched in May and June 2020 using variations of the terms “air pollution” and “seizures,” without limits on date or language of publication. Observational or ecological studies were included if they studied the effect of exposure to at least one outdoor air pollutant, such as particulate matter (PM2.5 and PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ground-level ozone (O3), on the risk of non-febrile seizures or epilepsy. Risk of bias was assessed using the Tool to Assess Risk of Bias in Case-Control Studies by the CLARITY group at McMaster University, Canada. Results: The search retrieved 11,191 citations, 13 were selected for full-text screening, and six were included in the final synthesis. The risk of seizures was significantly associated with PM2.5 in one of five studies, with PM10 in two of six, SO2 in two of five, NO2 in three of five, N2O in one of one study, and O3 in two of four studies. All significant associations indicated an increased risk of seizures associated with higher pollutant concentration, except for one study that reported a protective effect of O3. The risk of bias was low on all items except for control of confounding, for which all six studies were graded a medium risk or higher. Conclusions: The effect of PM2.5, N2O, and O3 exposure on seizure risk remains unclear; however, there is evidence suggesting that PM10, SO2, and NO2 exposure may significantly increase risk. Confounding by weather, co-pollutants, and individual-level variables should be carefully controlled in future studies seeking to address this question. Funding: Please list any funding that was received in support of this abstract.: Lawson Health Research Institute, Western University and its Schulich School of Medicine and Dentistry, the Jack Cowin Endowed Chair in Epilepsy Research.