Cohort study on circumcision of newborn boys and subsequent risk of urinary-tract infection

Abstract

Background: A decrease in risk of urinary-tract infection is one of the most commonly given reasons for circumcision of newborn boys. Previous studies have reported rates of UTI to be 10-20 times higher in uncircumcised than in circumcised boys. This population-based cohort study followed neonates in Ontario, Canada, prospectively to study the relation between circumcision and subsequent UTI risk.

Methods: Eligible boys were born to residents of Ontario between April 1, 1993, and March 31, 1994. We used hospital discharge data to follow up boys until March 31, 1996.

Findings: Of 69,100 eligible boys, 30,105 (43.6%) were circumcised and 38,995 (56.4%) uncircumcised. 888 boys circumcised after the first month of life were excluded. 29,217 uncircumcised boys were matched to the remaining circumcised boys by date of birth. The 1-year probabilities of hospital admission for UTI were 1.88 per 1000 person-years of observation (83 cases up to end of follow-up) in the circumcised cohort and 7.02 per 1000 person-years (247 cases up to end of follow-up) in the uncircumcised cohort (p<0.0001). The estimated relative risk of admission for UTI by first-year follow-up indicated a significantly higher risk for uncircumcised boys than for circumcised boys (3.7 [2.8-4.9]). 195 circumcisions would be needed to prevent one hospital admission for UTI in the first year of life.

Interpretation: Although our findings support the notion that circumcision may protect boys from UTI, the magnitude of this effect may be less than previously estimated.

PIP: A prospective population-based cohort study assessed the association between male circumcision and subsequent urinary tract infection (UTI) in children born in Ontario, Canada, in a 12-month period in 1993-94. Of the 69,100 eligible infants, 30,105 (43.6%) were circumcised in the first month of life. 29,217 uncircumcised boys were matched to circumcised boys by date of birth and followed for 24-36 months. Information on UTIs was extracted from the Canadian Institute for Health Information computerized database on hospital discharges. There were 83 UTI cases in the circumcised cohort (1.88/1000 person-years of observation) and 247 in the uncircumcised group (7.02/1000 person-years) (p 0.0001). The relative risk of UTI in uncircumcised compared to circumcised boys was 4.5 (95% CI, 2.4-8.4) in the first month of life and 3.7 (95% CI, 2.8-4.9) in the year after the procedure. Calculation of the attributable risk indicated 195 circumcisions would be necessary to prevent one admission for UTI in the first year of life. Previous studies have recorded UTI rates 10-20 times higher in uncircumcised than circumcised boys. These findings support the hypothesis that circumcision protects boys from UTI, but the magnitude of this effect may be less than previously estimated.