VAGINAL oestrogen is considered the standard treatment for recurrent urinary tract infections (UTI) in females with hypoestrogenism. However, literature exploring its use is limited, with narrow generalisability. A research team at Kaiser Permanente, San Diego, California, USA, therefore sought to investigate the association between vaginal oestrogen prescription and UTI frequency. Further objectives included the exploration of predictors of post-prescription UTI infection and medication adherence.
The multicentre retrospective review included 5,638 females with a baseline UTI infection frequency of 3.9 (±standard deviation=1.3). All participants had been prescribed vaginal oestrogen between January 2009–December 2019, with recurrent UTI defined as ≥3 positive urine cultures (separated by at least 14 days) in the 12 months preceding the index vaginal oestrogen prescription.
Demographic, medical comorbidities, and surgical history data was collected along with adherence through refill data. A paired t-test compared pre- and post-prescription UTI infection rates with binomial regression used to evaluate predictors of post-prescription UTI.
The mean UTI frequency in the year following the index prescription decreased by 1.8 (p<0.001), a 51.9% reduction, with 55.3% and 31.4% of patients experiencing ≤1 or no UTIs, respectively. Significant predictors of UTI infection included age of 75–84 years (incident rate ratio: 1.24; 95% confidence interval: 1.05–1.46) and >85 years (1.41; 1.17–1.68), increased baseline UTI frequency (1.22; 1.19–1.24), diabetes (1.14; 1.07–1.21), urinary retention (1.21; 1.10–1.33), urinary incontinence (1.14; 1.07–1.21), and moderate (1.32; 1.23–1.42) or high medication adherence (1.33; 1.24–1.42). Finally, participants with high medication adherence demonstrated more frequent post-prescription UTI than those with low adherence (2.2 versus 1.6; p<0.0001).
In conclusion, the prescription of vaginal oestrogen was associated with a 50% decrease in the frequency of UTI. However, the paradoxical finding that females with moderate and high medication adherence demonstrated the lowest reduction in UTI frequency may represent unobserved selection or unmeasured cofounding. The team also noted that: “Although antibiotics are the mainstay of treatment, a focus on prevention is important to avert disruption of the urinary microbiome, prevent multidrug resistance of bacterial pathogens, avoid adverse side effects, and reduce costs.”