Study Highlights

• The investigators derived data from patients enrolled in 7 Blue Cross and Blue Shield health plans in the United States.
• These plans included the states of Hawaii, Michigan, North Carolina, Tennessee, Iowa, South Dakota, and Pennsylvania.
• The dataset included 3.7 million insured lives during a 5-year period (2002-2006) with information on sex, age, enrollment dates, and claims for reimbursement for services.
• Included in this study were claims identified by diagnostic codes using the International Classification of Diseases, Ninth Revision, and diagnosis-related groups. Medical procedures were classified by the current procedural terminology coding system.
• A subset of 95,598 patients completed Health Risk Assessment documents that included their BMI.
• 30.6% of patients completed the assessments more than once during the 5-year period.
• Excluded were those who did not complete the Health Risk Assessments.
• Also excluded were women reporting pregnancy during the year and the year before and after the Health Risk Assessment.
• A UTI diagnosis included codes for both cystitis and UTI.
• A diagnosis of pyelonephritis included both acute and chronic pyelonephritis.
• The BMI reported closest to the diagnosis of UTI or pyelonephritis or the highest BMI reported was used for each patient.
• 6 BMI strata were used, from less than 30 kg/m² to 50 kg/m² or higher.
• The dependent variable was a diagnosis of UTI or pyelonephritis, and logistic regression was used to analyze by age, sex, and BMI.
• Among the 95,598 patients who were analyzed, 57.1% were women.
• 3.7% of men and 18.4% of women had a BMI of less than 30 kg/m², and 7.5% of men and 21.9% of women had BMI of more than 50 kg/m².
• In the overall cohort, UTI was diagnosed in 13.0% of participants and pyelonephritis in 0.84% at 5 years.
• Women were 4.2 times more likely to be diagnosed with a UTI than men (19.3% vs 4.6%).
• Women were also 3.6 times more likely than men to be diagnosed with pyelonephritis (1.22% vs 0.34%).
• At all strata of obesity, the diagnosis of UTI was more likely to occur in obese vs nonobese participants.
• For pyelonephritis, the risk associated with obesity varied for each stratum of obesity, and not all strata showed an increased risk.
• As a group, obese participants were 4.5 times more likely than nonobese participants to be diagnosed with UTIs, and men were at higher risk for obesity-associated UTIs overall.
• Obese patients were 5 times more likely than nonobese patients to be diagnosed with pyelonephritis, and women had a higher risk for obesity-associated pyelonephritis.
• In men, the odds ratio for UTI varied from 1.59 to 2.47 for different strata of obesity.
• In women, the odds ratio for UTI varied from 1.05 to 1.24 for different strata of obesity.
• The authors concluded that a BMI of 30 kg/m² or higher was associated with increased risks for UTI and pyelonephritis in both men and women but that men were at higher risk for obesity-associated UTIs overall, and women are at higher risk for obesity-associated pyelonephritis.
• They recommended that reduction in the risks for UTI and pyelonephritis may be another incentive for weight loss among patients with obesity.