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A high sensitivity of children to swimming associated gastrointestinal illness (response to letter by Linn)
Citation:
WADE, T. J., E. A. SAMS, K. P. BRENNER, R. A. HAUGLAND, L. J. WYMER, AND A. P. DUFOUR. A high sensitivity of children to swimming associated gastrointestinal illness (response to letter by Linn). EPIDEMIOLOGY. Lippincott Williams & Wilkins, Philadelphia, PA, 20(1):157, (2009).
Impact/Purpose:
research results
Description:
We disagree with Mr. Linn’s interpretation of our paper, “High Sensitivity of Children to Swimming-Associated Gastrointestinal Illness”.1 His comments are focused on hypothetical interpretation of our results as related to criteria development rather than the science presented. Mr. Linn notes our definitions for gastrointestinal (GI) illness and swimming differ from those used previously.2,3 We clearly justify our rationale for both definitions, and we reject the implication that it is misleading to revisit these definitions, previously used in studies done over 20 years ago. An independent peer review supported these changes, as well as additional changes described below. We make no attempt, as Mr. Linn implies, to establish an “illness rate threshold” for comparison with current criteria. We explicitly do not make any such comparison due to substantial differences in the current study compared to previous studies.2,3 These differences include several aspects of the basic study design including the follow-up period, statistical methodology, definitions of illness as well as the indicators and methods used. These differences make simplistic, direct comparisons problematic, and Mr. Linn’s attempts at such direct comparisons are not justified. The enhanced sensitivity among children is clearly presented. By highlighting a small range of data, Mr. Linn ignores the overall effect. As Mr. Linn points out, the difference between swimming and non-swimming children is less than that between all swimmers and non-swimmers in water of good microbial quality as measured by Enterococcus QPCR CE, reflecting baseline characteristics and differences between swimming and non-swimming children. This says nothing of the susceptibility of children to GI illness associated with swimming in water of poor microbial quality. With increasing exposure to Enterococcus QPCR CE, the risk of illness among swimming children increases at a greater rate compared to other age groups. The odds of illness among swimming children increased 69% with every log increase in Enterococcus QPCR CE exposure, whereas the odds of illness among those aged 11-54 years and those 55 years and over increased 13% and 21%, respectively (See Table 51). We do not suggest that “…the sensitivity of children warrants adjustment of recreational water quality criteria”. Our conclusion was limited to the study itself and was presented in the following discussion: “…children up to age 10 years were especially susceptible to GI illness following swimming exposure. ..this is the first study to demonstrate this sensitivity as a function of microbial water quality.” 1. Wade TJ, Calderon RL, Brenner KP, Sams E, Beach M, Haugland R, Wymer L, Dufour AP. High sensitivity of children to swimming-associated gastrointestinal illness: results using a rapid assay of recreational water quality. Epidemiology 2008;19(3):375-83. 2. Cabelli V. Health effects criteria for marine recreational waters. Cincinnati, OH: US Environmental Protection Agency, 1983. 3. Dufour A. Health effects criteria for fresh recreational waters. Cincinnati, OH: US Environmental Protection
