A case-control study of medium-term exposure to ambient nitrogen dioxide pollution and hospitalization for stroke

Abstract

BackgroundThere are several plausible mechanisms whereby either short or long term exposure to pollution can increase the risk of stroke. Over the last decade, several studies have reported associations between short-term (day-to-day) increases in ambient air pollution and stroke. The findings from a smaller number of studies that have looked at long-term exposure to air pollution and stroke have been mixed. Most of these epidemiological studies have assigned exposure to air pollution based on place of residence, but these assignments are typically based on relatively coarse spatial resolutions. To date, few studies have evaluated medium-term exposures (i.e, exposures over the past season or year). To address this research gap, we evaluated associations between highly spatially resolved estimates of ambient nitrogen dioxide (NO2), a marker of traffic pollution, and emergency department visits for stroke in Edmonton, Canada.MethodsThis was a case-control study with cases defined as those who presented to an Edmonton area hospital emergency department between 2007 and 2009 with an acute ischemic stroke, hemorrhagic stroke, or transient ischemic attack. Controls were patients who presented to the same emergency departments for lacerations, sprains, or strains. A land-use regression model provided estimates of NO2 that were assigned to the place of residence. Logistic regression methods were used to estimate odds ratios for stroke in relation to an increase in the interquartile range of NO2 (5 ppb), adjusted for age, sex, meteorological variables, and neighborhood effects.ResultsThe study included 4,696 stroke (cases) and 37,723 injury patients (controls). For all strokes combined, there was no association with NO2. Namely, the odds ratio associated with an interquartile increase in NO2 was 1.01 (95% confidence interval {CI}: 0.94-1.08). No associations were evident for any of the stroke subtypes examined.ConclusionWhen combined with our earlier work in Edmonton, our findings suggest that day-to-day fluctuations in air pollution increase the risk of ischemic stroke during the summer season, while medium term exposures are unrelated to stroke risk. The findings for medium term exposure should be interpreted cautiously due to limited individual-level risk factor data.

Associations between exhaust and non-exhaust particulate matter and stroke incidence by stroke subtype in South London

“…The potential differential effect of particulate matter from exhaust and non-exhaust sources is an areas which warrants further investigation. The lack of association observed between long-term exposure and risk all ischaemic or haemorrhagic stroke is in line with findings from previous studies (Johnson et al, 2013;Johnson et al, 2010;Maheswaran et al, 2012). Only one study of the long-term effects found a significant increased risk of haemorrhagic stroke associated with long-term exposure to N0 2 in Japan (Yorifuji et al, 2013).…”

“…concentrations averaged over months or years, usually measured at place of residence. Some studies found no associations with stroke risk (Johnson et al, 2013;Maheswaran et al, 2014;Maheswaran et al, 2012;Yorifuji et al, 2013). The European ESCAPE cohort study found a 5-μg/ m3 increase in annual PM 2.5 exposure associated with 19% increased risk of incident stroke, with similar findings for PM 10 (Stafoggia et al, 2014).…”

“…In 2010 it is estimated 17 million first strokes occurred, an increase of 68% since 1990 (Feigin et al, 2014). The contribution of outdoor air pollution to stroke risk has been increasingly studied in recent years (Henrotin et al, 2007;Johnson et al, 2013;Johnson et al, 2010;Leiva et al, 2013;Lisabeth et al, 2008;Maheswaran et al, 2014;Maheswaran et al, 2012;Maheswaran et al, 2010;Qian et al, 2013;Wellenius et al, 2012;Yorifuji et al, 2013;Yorifuji et al, 2014;Yu et al, 2014).…”

Ambient Air Pollution and Stroke

“…Most commonly reported pollutants included long-term exposure to PM 10 6, 10, 14, 15 , PM 2.5 10, 11, 16 and NO x 6, 17, 18 or NO 2 8, 14, 15, 19, 20 . Many of the cohort studies reported positive associations 8, 10, 11, 14, 21 whereas ecological studies 6, 15, 19 and case-control studies 17, 18, 21 showed mixed results. In a random-effects meta-analysis of 11 European cohorts 16 , long-term PM 2.5 was associated more strongly associated with stroke in subjects older than 60 years old, never-smokers and among subjects with exposure levels less than 25 µg/m 3 (current annual mean air quality standard in Europe).…”

A Review on the Impacts of the Air Pollution on the public Health: A Case for Different Metropolises around the World

“…This reason suggests an environmental etiology for atherosclerosis [12]. At the same time, a Canadian study found a greater association between short-term exposure and the development of stroke [13].…”