Outdoor air pollution and stroke in Sheffield, United Kingdom: a small-area level geographical study.
OBJECTIVE
Current evidence suggests that stroke mortality and hospital admissions should be higher in areas with elevated levels of outdoor air pollution because of the combined acute and chronic exposure effects of air pollution. We examined this hypothesis using a small-area level ecological correlation study.


METHODS
We used 1030 census enumeration districts as the unit of analysis and examined stroke deaths and hospital admissions from 1994 to 1998, with census denominator counts for people > or =45 years. Modeled air pollution data for particulate matter (PM10), nitrogen oxides (NO(x)), and carbon monoxide (CO) were interpolated to census enumeration districts. We adjusted for age, sex, socioeconomic deprivation, and smoking prevalence.


RESULTS
The analysis was based on 2979 deaths, 5122 admissions, and a population of 199 682. After adjustment for potential confounders, stroke mortality was 37% (95% CI, 19 to 57), 33% (95% CI, 14 to 56), and 26% (95% CI, 10 to 46) higher in the highest, relative to the lowest, NO(x), PM10, and CO quintile categories, respectively. Corresponding increases in risk for admissions were 13% (95% CI, 1 to 27), 13% (95% CI, -1 to 29), and 11% (95% CI, -1 to 25).


CONCLUSIONS
The results are consistent with an excess risk of stroke mortality and, to a lesser extent, hospital admissions in areas with high outdoor air pollution levels. If causality were assumed, 11% of stroke deaths would have been attributable to outdoor air pollution. Targeting policy interventions at high pollution areas may be a feasible option for stroke prevention.
Maheswaran
Ravi
R
Public Health GIS Unit, School of Health and Related Research, the University of Sheffield, Regent Court, 30 Regent Street, Sheffield S1 4DA, United Kingdom. r.maheswaran@sheffield.ac.uk
Haining
Robert P
RP
Brindley
Paul
P
Law
Jane
J
Pearson
Tim
T
Fryers
Peter R
PR
Wise
Stephen
S
Campbell
Michael J
MJ
D000367:Age Factors; D000368:Aged; D000393:Air Pollutants / Q000737:chemistry; D000397:Air Pollution; D002248:Carbon Monoxide / Q000032:analysis / Q000737:chemistry; D002561:Cerebrovascular Disorders / Q000453:epidemiology / Q000209:etiology*; D004463:Ecology; D004781:Environmental Exposure; D005260:Female; D005843:Geography; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009569:Nitric Oxide / Q000737:chemistry; D016017:Odds Ratio; D012306:Risk; D012307:Risk Factors; D012737:Sex Factors; D017062:Small-Area Analysis; D012907:Smoking; D020521:Stroke / Q000453:epidemiology / Q000209:etiology*; D013997:Time Factors; D006113:United Kingdom; D014504:Urban Health
D000393:Air Pollutants; D009569:Nitric Oxide; D002248:Carbon Monoxide