Risk Factors for Second Urinary Tract Infection among College Women
Am J Epidemiol
Risk Factors for Second Urinary Tract Infection among College Women
Betsy Foxman 0
Brenda Gillespie 0
James Koopman 0
Lixin Zhang 0
Karen Palin 0
Patricia Tallman 0
Jane V. Marsh 0
Scott Spear 0
Jack D. Sobel 0
M. Joan Marty 0
Carl F. Marrs 0
0 Reprint requests to Dr. Betsy Foxman, Department of Epidemiology , 109 Observatory Street Ann A/bor, Ml 48109-2029 (
To better understand the etiology of recurrent urinary tract infection (UTI), the authors followed a cohort of 285 female college students with first UTI for 6 months or until second UTI. A first UTI due to Escherichia coli was followed by a second UTI three times more often than was a non-E. coli first UTI (24 vs. 8%; p = 0.02). In a logistic regression analysis limited to the 224 women from the University of Michigan Health Service and the University of Texas at Austin Health Service from September 1992 to December 1994, with a first UTI due to E. coli, vaginal intercourse increased the risk of a second UTI with both a different (odds ratio (OR) = 1.60, 95% confidence interval (Cl): 1.19, 2.15) and the same (OR = 1.37, 95% Cl: 0.91, 2.07) uropathogen, as did using a diaphragm, cervical cap, and/or spermicide (same uropathogen: OR = 1.53, 95% Cl: 0.95, 2.47; different uropathogen: OR = 1.77, 95% Cl: 1.22, 2.58). Condom use decreased the risk of a second UTI caused by a different uropathogen (OR = 0.68, 95% Cl: 0.48, 0.99) but had no effect on a second UTI caused by the same E. coli (OR = 0.99; 95% Cl: 0.66, 1.50). Type or duration of treatment was not associated with a second UTI. Although the risk of second UTI is strongly influenced by sexual behavior, women with a first UTI caused by E. coli are more likely than are those with a non-E. coli first UTI to have a second UTI within 6 months. Am J Epidemiol 2000;151:1194-1205. Escherichia coir, recurrence; risk factors; sex behavior; urinary tract infections; women
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Each year, approximately 7.3 million women visit a
clinician for urinary tract infections (UTI) (National
Center for Health Statistics, unpublished data, 1995).
Half of all women will have at least one UTI by age 30
years (
1
), an estimated 20-30 percent of women with
a first UTI will have two or more episodes (
2
), and 5
percent will have chronic recurring infections (
3
). The
relative roles of host and bacterial factors on risk of
second or repeated UTI are not well understood.
Most studies of UTI pathogenesis include women
with culture-confirmed, symptomatic infections
regardless of the number of prior UTI. History of
prior UTI is a strong predictor of acquiring
subsequent infection (
4, 5
): the 6-month risk of second UTI
is an order of magnitude greater than the risk of UTI
Received for publication March 16, 1999, and accepted for
publication August 5, 1999.
Abbreviations: Cl, confidence interval; OR, odds ratio; RR, rate
ratio; UTI, urinary tract Infection.
1 Department of Epidemiology, University of Michigan School of
Public Hearth, Ann Arbor, Ml.
2 Center for Statistical Consultation and Research, University of
Michigan, Ann Arbor, Ml.
3 Department of Biology, Bates College, Lewiston, ME.
4 Department of Pediatrics, University of Wisconsin, Madison, Wl.
5 Division of Infectious Diseases, Wayne State University, Detroit,
Ml.
in the general population (
2
). One third (
5
) to one half
of recurring UTI are due to the previous infecting
organism (
6
), making it difficult to separate risk
factors for acquiring new uropathogens (that lead to
symptoms) from risk factors for developing
symptoms from an existing colonization. Although the
number of prior UTI can be adjusted for in the
analysis, statistical adjustment summarizes overall
categories of other variables, potentially obscuring
important effects. For example, a risk factor for
colonization with a uropathogen—a crucial first step that
might be subject to intervention—may have little or
no effect on risk of recurrent symptomatic infection.
The effects of this factor would remain undetected if
first UTI were not examined separately.
Combining first and subsequent UTI is especially
problematic when addressing bacterial virulence
factors. A bacterial virulence factor may be associated
with risk of first UTI but be associated with decreased
risk of second or multiple UTI (
6
). Virulence factors
leading to first UTI may protect against second UTI by
stimulating host response to those factors, or chronic,
recurring infection due to the same bacteria may signal
a failure in host response. One third of the women with
community-acquired Escherichia coli UTI have
subsequent UTI caused by the same strain (
5
). Among
women with recurring UTI, 68 percent may have a
recurrence caused by the same strain (
7
).
To understand better the pathogenesis of UTI, we
followed a cohort of 285 women with first UTI for 6
months or until the second UTI. This standardized
prior history of UTI and allowed us to determine
whether the behavioral factors for the (...truncated)