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Long term risk for hypertension, renal impairment, and cardiovascular disease after gastroenteritis from drinking water contaminated with Escherichia coli O157:H7: a prospective cohort study

BMJ 2010; 341 doi: (Published 18 November 2010) Cite this as: BMJ 2010;341:c6020
  1. William F Clark, professor of nephrology12,
  2. Jessica M Sontrop, assistant professor of epidemiology123,
  3. Jennifer J Macnab, assistant professor of epidemiology3,
  4. Marina Salvadori, associate professor of infectious disease4,
  5. Louise Moist, associate professor of nephrology and epidemiology123,
  6. Rita Suri, assistant professor of nephrology12,
  7. Amit X Garg, associate professor of nephrology and epidemiology123
  1. 1Division of Nephrology, Department of Medicine, London Health Sciences Centre, London, ON, Canada
  2. 2London Kidney Clinical Research Unit, London Health Sciences Centre, London, ON
  3. 3Department of Epidemiology and Biostatistics, University of Western Ontario, London, ON
  4. 4Department of Pediatric Infectious Diseases, Children’s Hospital, London Health Sciences Centre, London, ON
  1. Correspondence to: W F Clark, A2-343 Westminster Tower, Victoria Hospital, 800 Commissioner’s Road East, London, ON, Canada N6A 4G5 William.Clark{at}
  • Accepted 8 September 2010


Objectives To evaluate the risk for hypertension, renal impairment, and cardiovascular disease within eight years of gastroenteritis from drinking water contaminated with Escherichia coli O157:H7 and Campylobacter.

Design A prospective cohort study.

Setting Walkerton, Ontario, Canada.

Participants 1977 adult participants in the Walkerton Health Study recruited between 2002 and 2005 after an outbreak of gastroenteritis in May 2000, when a municipal water system was contaminated, with no pre-outbreak history of outcome measures.

Outcome measures Information was collected annually via survey, physical examination, and laboratory assessment. Primary measures were acute gastroenteritis (diarrhoeal illness lasting >3 days, bloody diarrhoea, or >3 loose stools/day), hypertension (blood pressure ≥140/90 mm Hg), and renal impairment (microalbuminuria or estimated glomerular filtration rate <60 ml/min/1.73 m2). Self reported physician diagnosis of cardiovascular disease (myocardial infarction, stroke, or congestive heart failure) was a secondary outcome.

Results Acute gastroenteritis at the time of the outbreak was reported by 1067 (54%) of participants. Incident hypertension was detected in 697 (35%) (294 (32%) of group not exposed to acute gastroenteritis v 403 (38%) of exposed group). While 572 (29%) had at least one indicator of renal impairment (266 (29%) of unexposed v 306 (29%) of exposed), only 30 (1.5%) had both (8 (0.9%) of unexposed v 22 (2.1%) of exposed). Cardiovascular disease was reported by 33/1749 (1.9%). The adjusted hazard ratios for hypertension and cardiovascular disease after acute gastroenteritis were 1.33 (95% confidence interval 1.14 to 1.54) and 2.13 (1.03 to 4.43) respectively. The adjusted hazard ratio for the presence of either indicator of renal impairment was 1.15 (0.97 to 1.35) and was 3.41 (1.51 to 7.71) for the presence of both.

Conclusion Gastroenteritis from drinking water contaminated with E coli O157:H7 and Campylobacter was associated with an increased risk for hypertension, renal impairment, and self reported cardiovascular disease. Annual monitoring of blood pressure and periodic monitoring of renal function may be warranted for individuals who experience E coli O157:H7 gastroenteritis.


  • We thank the participants of the Walkerton Health Study, who have freely given of themselves to participate over an extended period after tragic circumstances. We also thank Ms Arlene Richards and the staff of the Walkerton Health Study for their efforts in ensuring accurate and timely data collection.

  • Contributors: All authors participated in the conception and design of the study and in the critical revision of the manuscript for important intellectual content. WFC, MS, and AXG obtained funding for the study. WFC, JJM, MS, LM, RS, and AXG participated in data acquisition. JMS and JJM performed the data analysis. WFC, JMS, JJM, LM, and AXG interpreted the data. WFC, JMS, JJM produced the draft of the manuscript. All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. WFC is guarantor for the study.

  • Funding: This study was funded by the Ontario Ministry of Health and Long term Care, which had no role in design and conduct of the study; collection, analysis, and interpretation of the data; or preparation, review, or approval of the manuscript.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare that (1) no authors have received support from any companies for the submitted work; (2) no authors have any relationships with any companies that might have an interest in the submitted work in the previous 3 years; (3) their spouses, partners, or children have no financial relationships that may be relevant to the submitted work; and (4) no authors have non-financial interests that may be relevant to the submitted work.

  • Ethical approval: Participants provided written informed consent, and ethical approval was obtained from the University of Western Ontario’s Research Ethics Board for Health Sciences.

  • Data sharing: The technical appendix, statistical code, and dataset are available from the corresponding author,

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