"Excess Water Damages Kidneys" (the Walkerton Health Study)

The news media is suddenly reporting that drinking water is bad for you. This report is apparently a misinterpretation of the soon-to-be-released results of the Walkerton Health Study, which showed high levels of chronic kidney disease in a town years after an outbreak of E. Coli 0157:H7 in patients who drank the water but did not have clinical evidence of hemolytic uremic syndrome. More to follow.

Update (11/19/05): Here's an earlier paper, "Risk of hypertension and reduced kidney function after acute gastroenteritis from bacteria-contaminated drinking water." Here's the abstract:

Background: The long-term health consequences of acute bacterial gastroenteritis remain uncertain. We studied the risk of hypertension and reduced kidney function after an outbreak of acute gastroenteritis due to contamination of a regional drinking water supply with Escherichia coli O157:H7 and Campylobacter species.

Methods: A total of 1958 adults with no known history of hypertension or kidney disease before the outbreak participated in a long-term follow-up study. Of the participants, 675 had been asymptomatic during the outbreak, 909 had had moderate symptoms of acute self-limited gastroenteritis, and 374 had had severe symptoms that necessitated medical attention. The outcomes of interest were a diagnosis of hypertension or the presence of reduced kidney function and albuminuria during the follow-up period.

Results: After a mean follow-up of 3.7 years after the outbreak, hypertension was diagnosed in 27.0% of participants who had been asymptomatic during the outbreak and in 32.3% and 35.9% of those who had had moderate and severe symptoms of acute gastroenteritis respectively (trend p = 0.009). Compared with the asymptomatic participants, those with moderate and severe symptoms of gastroenteritis had an adjusted relative risk of hypertension of 1.15 (95% confidence interval [CI] 0.97–1.35) and 1.28 (95% CI 1.04–1.56) respectively. A similar graded association was seen for reduced kidney function, defined as the presence of an estimated glomerular filtration rate below 60 mL/min per 1.73 m2 (trend p = 0.03). No association was observed between gastroenteritis and the subsequent risk of albuminuria.

Interpretation: Acute bacterial gastroenteritis necessitating medical attention was associated with an increased risk of hypertension and reduced kidney function 4 years after infection. Maintaining safe drinking water remains essential to human health, as transient bacterial contaminations may have implications well beyond a period of acute self-limited illness.

Technorati Tags: Walkerton, Hemolytic Uremic Syndrome, Kidney Disease, Walkerton Health Study, E. Coli