Ambient Sulphur Dioxide and Female ED Visits for Migraine

Migraine and air pollution: A systematic review

OBJECTIVE

To systematically synthesize evidence from a broad range of studies on the association between air pollution and migraine.

BACKGROUND

Air pollution is a ubiquitous exposure that may trigger migraine attacks. There has been no systematic review of this possible association.

METHODS

We searched for empirical studies assessing outdoor air pollution and any quantified migraine outcomes. We included short- and long-term studies with quantified air pollution exposures. We excluded studies of indoor air pollution, perfume, or tobacco smoke. We assessed the risk of bias with the World Health Organization's bias assessment instrument for air quality guidelines.

RESULTS

The final review included 12 studies with over 4,000,000 participants. Designs included case-crossover, case-control, time series, and non-randomized pre-post intervention. Outcomes included migraine-related diagnoses, diary records, medical visits, and prescriptions. Rather than pooling the wide variety of exposures and outcomes into a meta-analysis, we tabulated the results. Point estimates above 1.00 reflected associations of increased risk. In single-pollutant models, the percent of point estimates above 1.00 were carbon monoxide 5/5 (100%), nitrogen dioxide 10/13 (78%), ozone 7/8 (88%), PM2.5 13/15 (87%), PM10 2/2 (100%), black carbon 0/1 (0%), methane 4/6 (75%), sulfur dioxide 3/5 (60%), industrial toxic waste 1/1 (100%), and proximity to oil and gas wells 6/13 (46%). In two-pollutant models, 16/17 (94%) of associations with nitrogen dioxide were above 1.00; however, more than 75% of the confidence intervals included the null value. Most studies had low to moderate risks of bias. Where differences were observed, stronger quality articles generally reported weaker associations.

CONCLUSIONS

Balancing the generally strong methodologies with the small number of studies, point estimates were mainly above 1.00 for associations of carbon monoxide, nitrogen dioxide, ozone, and particulate matter with migraine. These results were most consistent for nitrogen dioxide.

Epidemiology and treatment utilization for Canadian patients with migraine: a literature review

The objective of this narrative review was to identify real-world evidence regarding the burden of migraine in Canada. We conducted a literature search in MEDLINE, Embase, and the Cochrane Database of Systematic Reviews for studies published between August 2010 and August 2020. Of the 3269 publications identified, 29 studies were included. Prevalence estimates varied widely across Canada, and mental health comorbidities were common. Individuals with migraine have a lower quality of life, detrimental impact on workforce productivity, and higher rates of health care resource utilization (HCRU), with HCRU and costs highest among those with chronic migraine. We found inconsistencies in care, including underutilization of medications such as triptans, and varied utilization of over-the-counter and prescription medications. Increased medication use was identified among those with chronic migraine, and only a small number of patients used migraine preventive medications. The burden of migraine in Canada is substantial. Reduced quality of life and workforce productivity, increased HCRU and costs, and underutilization of triptans and migraine preventive medications highlight an important need for more effective management of individuals with migraine.

Weather, ambient air pollution, and risk of migraine headache onset among patients with migraine

OBJECTIVE

Migraine is a common recurrent headache disorder affecting 14% American adults. Although weather and air pollution are often reported by patients with migraine as precipitating factors, previous studies have had mixed results.

METHODS

We prospectively collected migraine headache onset data using electronic questionnaires from 98 adults with episodic migraine in the Greater Boston area (2016-2017). Each participant was followed for an average of 45 days for a total of 4406 days of observation. Temperature, relative humidity, and barometric pressure data were obtained from local weather station. Daily average fine particulate matter, daily maximum 1-hour sulfur dioxide, daily maximum 1-hour nitrogen dioxide, daily maximum 8-hour ozone, and daily maximum 8-hour carbon monoxide from local air pollution monitors. We conducted a repeated measures analysis using fixed effects logistic regression models. In the models we adjusted for day of week, a natural cubic spline term of day of the year with 4 degrees of freedom, and a participant identifier. We additionally adjusted for linear terms of temperature and relative humidity in the air pollution analyses. We also applied logistic regression models with generalized estimating equation (GEE) and autoregressive correlation structure in the sensitivity analysis.

RESULTS

The mean age was 35 years and 88% were women. Mean temperature was 56.9 °F, relative humidity 67.3%, and fine particulate matter 7.3 μg/m³. Higher relative humidity was associated with higher odds of migraine headache, but the association was only observed in warm season (April-September). Higher levels of daily maximum 8-hour ozone and daily maximum 8-hour carbon monoxide appeared to be associated with higher odds of migraine headache onset in cold season (October-March). Although the associations for ozone and relative humidity were attenuated and no longer statistically significant in the overall GEE analysis, the differing associations by season remained.

CONCLUSIONS

We found that higher relative humidity was associated with higher odds of migraine headache onset in warm season, and traffic-related gaseous pollutants may be associated with higher odds of migraine headache onset in cold season.