NEW YORK, Jan 25 (Reuters Health) -- Even where drinking water standards meet state and federal standards, the elderly may be at increased risk for waterborne gastrointestinal infections from tap water, results of a recent study suggest.
Since hospitalizations and mortality associated with gastrointestinal illness is particularly high among this group, the findings could have significant social and economic implications in the coming years, the authors write in the Journal of Epidemiology and Community Health.
"Given the slow aging of the entire US population and the disproportionate burden of gastrointestinal disease in the elderly population, these costs can be expected to rise," conclude Dr. Joel Schwartz of the Harvard School of Public Health in Boston, Massachusetts, and colleagues.
Their study looked at the association between water quality and hospitalizations due to gastrointestinal illness among Philadelphia residents aged 65 years and older in the period 1992 - 1993. According to the investigators, the city's water system met guidelines set by the US Environmental Protection Agency (EPA) throughout the study period.
Still, "elderly residents of Philadelphia remain at risk of waterborne gastrointestinal illness under current water treatment practices." The researchers note that other studies have found an association between gastrointestinal disease and drinking water elsewhere in the US and Canada.
"Disinfected drinking water in Western countries may still be a source of infectious gastrointestinal illness," Schwartz and colleagues write.
They examined Medicare records of Philadelphia residents between 1992 and 1993, as well as daily water exposure measures. Records suggested a correlation between water quality and gastrointestinal illness 9 to 11 days prior to the hospital admission.
In an area serviced by one particular treatment plant, the association occurred after 4 to 6 days. Associations in all areas were stronger among patients over age 75 years, the study found.
Water quality was assessed by turbidity -- or the level of cloudiness of the water -- as determined by the EPA. Turbidity is used to gauge risk of microbial contamination and assess the effectiveness of the treatment of public drinking water.
However, disease-causing microorganisms are only a small fraction of the particles that can cause water to turn cloudy. Therefore, turbidity can only indicate -- not measure -- the true quality of water.
In an accompanying editorial, researchers from Spain note that a more comprehensive public health surveillance strategy is needed to control water quality and reduce the risk of waterborne gastrointestinal disease.
Such a system could include greater surveillance for cases of diarrhea and vomiting, particularly among high-risk groups like the elderly; standardization of laboratory detection; designating particular disorders as reportable to federal bureaus; and investigating and controlling waterborne outbreaks.