Ambient Sulphur Dioxide and Emergency Department Visits for Migraine and Depression

Aims: Depression and migraine are linked especially among women. Little previous research has focused on the potential association between ambient sulphur dioxide (SO2) exposure and emergency department (ED) visits for migraine, headache, depression, and anxiety.

Study Design: Case-crossover design, in which case and control is the same person, was used as study design for daily recorded diagnosed ED visits. Ambient sulphur dioxide was considered as an exposure.

Place and Duration of Study: ED data from five hospitals in Edmonton, Canada. The data were considered for the period: April 1, 1992 – March 31, 2002 (10 years).

Methodology: ED visits from Edmonton for the four health conditions were analyzed separately using case-crossover methodology. A conditional logistic regression was applied to implement a time-stratified case-crossover technique. The models were constructed for a single (one) air pollutant. Weather factors (temperature and humidity) were adjusted using natural splines. Odds ratios (ORs) and their 95% confidence intervals (CI) were estimated for an increase in an interquartile range of SO2 (IQR = 2.3 ppb).

Results: For females, statistically significant positive associations were observed between SO2 exposure and ED visits for migraine and depression (OR = 1.02, 95% CI: 1.01-1.03; OR = 1.04, 95% CI: 1.01-1.07, respectively). A positive association was observed for female ED visits for headache and anxiety. For males, ED visits for migraine were associated with ambient sulphur dioxide exposure (OR = 1.04, 95% CI: 1.00-1.08, for patients of age 20 to 60 years).

Conclusion: A known link between migraine and depression has its mapping in responses to ambient air pollution. These results provide additional evidence to indicate that ED visits for depressive disorder and migraine may be associated with exposure to ambient sulphur dioxide.