NEW YORK (Reuters Health) - Rates of urinary tract infection (UTI) and asymptomatic bacteriuria (AB) are higher among postmenopausal women with diabetes than among those without diabetes, researchers report. The cause does not seem to be related to neuropathy and residual urine volume, they found.

"No prospective data exist on the risk of microbiologically confirmed UTI and AB in relation to diabetes and its characteristics," Dr. Edward J. Boyko, of the University of Washington, Seattle, and colleagues write in the March 15th issue of the American Journal of Epidemiology.

To investigate, the researchers followed 218 diabetic and 799 non-diabetic women between the ages of 55 and 75 years for UTI and AB from 1998 to 2002. Urine culture, measurement of hemoglobin A1c, and post-void residual bladder volume were assessed at baseline and two annual follow-up examinations. Self-reports of UTI were confirmed by microbiologic culture and medical record review.

A total of 71 non-diabetic and 26 diabetic women developed UTI during follow-up, for an incidence of 6.7 and 12.2 per 100 person-years, respectively (relative risk = 1.8).

Corresponding rates for asymptomatic bacteriuria were 3.0 and 6.7 per 100 person-years (RR = 2.3).

Multivariable analysis demonstrated that the increased risk for UTI occurred primarily in women taking insulin (RR = 3.7) and in those with a longer duration of diabetes (at least 10 years; RR = 2.6) compared with nondiabetic women.

"These characteristics were also good predictors of other diabetes complications such as retinopathy or kidney disease," Dr. Boyko said in an interview with Reuters Health.

"We did not find an association between recent glucose control as reflected by the hemoglobin A1c measurement and risk of urinary tract infection," Dr. Boyko said. "This finding suggests that urinary tract infection may be due to long-term effect of high glucose as opposed to a shorter-term exposure to high glucose."

The team also investigated whether urine volume in the bladder after voiding explained the difference in risk of UTI in diabetic women, "since the nerve damage that may occur in diabetes leads to impaired emptying of the bladder," Dr. Boyko explained. "Although diabetic women had a greater post-void residual bladder volume on average than the non-diabetic women, we found that this difference did not explain the higher risk of UTI associated with diabetes."

Am J Epidemiol 2005;161:557-564.

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