Risk factors associated with acute pyelonephritis in healthy women

Background: Although most cases of acute pyelonephritis occur in otherwise healthy women, data on risk factors for this condition are lacking. Objective: To evaluate infection characteristics, incidence, and risk factors associated with acute pyelonephritis in a sample of women. Design: Population-based case-control study. Setting: Group Health Cooperative, a prepaid health plan in Washington. Participants: 788 nonpregnant women, 18 to 49 years of age. Case-patients (n = 242) were women with pyelonephritis who were identified from computerized databases. Controls were 546 similar-age women with no pyelonephritis diagnosis in the previous 5 years who were randomly selected from enrollment databases. Response rates for case-patients and controls were 73% and 64%, respectively. Measurements: Characteristics of infection and potential risk factors for pyelonephritis, ascertained through computer-assisted telephone interview and computerized databases. Results: 7% of case-patients were hospitalized. Escherichia coli was the infecting pathogen in 85% of cases. In multivariable models, factors associated with pyelonephritis risk were frequency of sexual intercourse in the previous 30 days (odds ratio, 5.6 [95% CI, 2.8 to 11.0] for >= 3 times per week), recent urinary tract infection (UTI) (odds ratio, 4.4 [CI, 2.8 to 7.1]), diabetes (odds ratio, 4.1 [CI, 1.6 to 10.9]), recent incontinence (odds ratio, 3.9 [CI. 2.6 to 5.9]), new sexual partner in the previous year (odds ratio, 2.2 [CI, 1.4 to 3.6]), recent spermicide use (odds ratio, 1.7 [CI, 1.1 to 2.8]), and UTI history in the participant's mother (odds ratio, 1.6 [CI, 1.1 to 2.5]). Risk factors for selected subgroups (patients <= 30 years of age, patients > 30 years of age, patients with no UTI history, and inpatients) were also evaluated. Limitations: Potential recall bias, reliance on automated case definition criteria, and limited data on diabetes and incontinence variables. Conclusions: Few nonpregnant, community-dwelling women younger than 50 years of age with pyelonephritis are hospitalized. As with cystitis in reproductive-age women, sexual behaviors and patient and family history of UTI are associated with increased pyelonephritis risk. Diabetes and incontinence also seem to independently increase the risk for pyelonephritis.