Journal Article

A Randomized, Controlled Trial of In-Home Drinking Water Intervention to Reduce Gastrointestinal Illness

John M. Colford, Timothy J. Wade, Sukhminder K. Sandhu, Catherine C. Wright, Sherline Lee, Susan Shaw, Kim Fox, Susan Burns, Anne Benker, M. Alan Brookhart, Mark van der Laan and Deborah A. Levy

in American Journal of Epidemiology

Published on behalf of Johns Hopkins Bloomberg School of Public Health

Volume 161, issue 5, pages 472-482
Published in print March 2005 | ISSN: 0002-9262
Published online March 2005 | e-ISSN: 1476-6256 | DOI:
A Randomized, Controlled Trial of In-Home Drinking Water Intervention to Reduce Gastrointestinal Illness

Show Summary Details


Trials have provided conflicting estimates of the risk of gastrointestinal illness attributable to tap water. To estimate this risk in an Iowa community with a well-run water utility with microbiologically challenged source water, the authors of this 2000–2002 study randomly assigned blinded volunteers to use externally identical devices (active device: 227 households with 646 persons; sham device: 229 households with 650 persons) for 6 months (cycle A). Each group then switched to the opposite device for 6 months (cycle B). The active device contained a 1-µm absolute ceramic filter and used ultraviolet light. Episodes of “highly credible gastrointestinal illness,” a published measure of diarrhea, nausea, vomiting, and abdominal cramps, were recorded. Water usage was recorded with personal diaries and an electronic totalizer. The numbers of episodes in cycle A among the active and sham device groups were 707 and 672, respectively; in cycle B, the numbers of episodes were 516 and 476, respectively. In a log-linear generalized estimating equations model using intention-to-treat analysis, the relative rate of highly credible gastrointestinal illness (sham vs. active) for the entire trial was 0.98 (95% confidence interval: 0.86, 1.10). No reduction in gastrointestinal illness was detected after in-home use of a device designed to be highly effective in removing microorganisms from water.

Keywords: drinking; epidemiologic studies; gastrointestinal diseases; intervention studies; randomized controlled trials; water; water supply; CDC, Centers for Disease Control and Prevention; CI, confidence interval; EPA, US Environmental Protection Agency; HCGI, highly credible gastrointestinal illness.

Journal Article.  6872 words.  Illustrated.

Subjects: Public Health and Epidemiology

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