Arsenic in drinking water and stroke hospitalizations in Michigan.
OBJECTIVE
Mechanistic and human studies suggest a role for arsenic in ischemic stroke; however, risks from chronic, low-level exposures are uncertain and US studies are lacking. The objective was to investigate the association between low-level arsenic exposure in drinking water and ischemic stroke hospital admissions in Michigan.


METHODS
Ischemic stroke hospital admissions among those aged ≥ 45 years were identified (1994 to 2006). Population-weighted average arsenic concentrations were estimated for each Michigan county (n = 83) and for zip codes in Genesee County (n=27) where there is greater variation in arsenic concentrations. US Census data provided age- and sex-specific population counts and other county- and zip code-level variables (race, income), which were adjusted for in multilevel negative binomial regression models of arsenic and stroke admissions. Hospital admissions for duodenal ulcer and hernia, not hypothesized to be associated with arsenic, were also evaluated.


RESULTS
Adjusted county-level analyses suggested a relationship between arsenic and ischemic stroke hospital admissions, although similar associations were observed for duodenal ulcer and hernia. In zip code-level analysis, arsenic was associated with an increased risk of stroke admission (relative risk, 1.03; 95% CI, 1.01 to 1.05 per μg/L increase in arsenic) after adjustment for confounders, and null or negative associations were found between arsenic and nonvascular outcomes.


CONCLUSIONS
Findings from this study suggest that exposure to even low levels of arsenic in drinking water may be associated with a higher risk of incident stroke. Given the ecological nature of the analysis, further epidemiological study with individual-level data on arsenic exposure and incident stroke is warranted.
Lisabeth
Lynda D
LD
Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI 48109, USA. llisabet@umich.edu
Ahn
Hyeong Jun
HJ
Chen
John J
JJ
Sealy-Jefferson
Shawnita
S
Burke
James F
JF
Meliker
Jaymie R
JR
D000368:Aged; D000369:Aged, 80 and over; D001151:Arsenic / Q000009:adverse effects*; D004381:Duodenal Ulcer / Q000453:epidemiology; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006547:Hernia / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D008824:Michigan / Q000453:epidemiology; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D020521:Stroke / Q000139:chemically induced* / Q000453:epidemiology*; D014873:Water Pollutants / Q000009:adverse effects*
D014873:Water Pollutants; D001151:Arsenic