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The Sonoma Water Evaluation Trial (SWET): A randomized drinking water intervention trial to reduce gastrointestinal illness in older adults
Citation:
Colford, J. M., J. F. Hilton, C. Wright, B. Arnold, S. Saha, T. J. WADE, J. W. Scott, AND J. N. Eisenberg. The Sonoma Water Evaluation Trial (SWET): A randomized drinking water intervention trial to reduce gastrointestinal illness in older adults. American Journal of Public Health. American Public Health Association, Washington, DC, 99(11):1988-1995, (2009).
Impact/Purpose:
research results
Description:
Objectives. We estimate the risk of highly credible gastrointestinal illness (HCGI) among adults 55 and older in a community drinking tap water meeting current U.S. standards. Methods. We conducted a randomized, triple-blinded, crossover trial in 714 households (988 individuals). Households were assigned randomly to active or sham water filtration devices for six months before switching to the opposite device for six months. We estimated the incidence rate ratio of HCGI episodes and the longitudinal prevalence ratio of HCGI days at the individual and population levels using generalized estimating equation (GEE) and generalized linear mixed models (GLMM), respectively, adjusted for covariates strongly associated with the outcome. Results. The adjusted incidence rate ratios of HCGI episodes per person-year (active vs. sham) were 0.88 (95% CI 0.77, 1.00) and 0.85 (95% CI 0.76, 0.94) in the GEE and GLMM models, respectively. The adjusted longitudinal prevalence ratios of days of HCGI (active vs. sham) per person-year were 0.88 (95% CI, 0.74, 1.05) and 0.84 (95% CI 0.78, 0.90) in the GEE and GLMM models, respectively. Conclusion There was a 12% -16% reduction in the incidence of highly credible gastrointestinal illness from use of the active device.
