Urinary Tract Infection - Risk Factors

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• With estrogen loss, the walls of the urinary tract thin out, weakening the mucous membrane and reducing its ability to resist bacteria. The bladder may lose elasticity and fail to empty completely.
• Estrogen loss has also been associated with reduction in certain immune factors in the vagina that help block E. coli from adhering to vaginal cells.
• Levels of lactobacilli (protective bacteria) decline after menopause, perhaps also due to drops in estrogen.

Some women carry the blood group P1, which as they get older, is associated with high levels of specific cells in the vagina and urethra that bind to a specific strain of E. coli that is resistant to normal infection-fighting mechanisms.

Other Risk Factors in Women. Women who have skin allergies to ingredients in soaps, vaginal creams, bubble baths, or other chemicals that are used in the genital area are at high risk for UTIs. In such cases, the allergies may cause small injuries that can introduce bacteria.

Risk Factors of Recurring Infection in Women

Most women who have had one UTI have occasional recurrences. About 25 - 50% of these women can expect another infection within a year of the previous one.

Between 3 - 5% of women, however, have ongoing, recurrent urinary tract infections, which follow the resolution of a previous treated or untreated episode. The major groups of women who are at highest risk for recurrent infections are young highly sexually active women and postmenopausal women. It might be argued that nearly all women who have a urinary tract infection are at risk for another, particularly if they are not treated for the first one.

Lifestyle Factors Increasing the Risk for Recurrence. Why urinary tract infections become chronic and recurring in many women is not entirely clear, but researchers are identifying certain lifestyle factors that may increase the risk in specific women:

• Engaging in sexual intercourse more than four times a month
• Recent changes in sexual partners
• Having a mother with a history of UTIs
• Having a first UTI before age 15
• Use of spermicides
• Smoking and taking tub baths may also increase the risk for recurrent urinary tract infections, but they are less significant than other risk factors.