Study design, materials and methods
Participants taking a diuretic were contacted via Researchmatch.org, a resource to help investigators find research volunteers. Participants were given a link to an anonymous REDCap survey. LUTS severity was measured with the Overactive Bladder Questionnaire-Short Form (OAB-q SF) . Adherence was assessed via three approaches. We used two validated adherence measures which produced continuous variable adherence scores (Adherence to Refills and Medications Scale and Self-Efficacy for Managing Medications and Treatments – Short Form) [2,3]. We then asked participants if they skip diuretic doses due to increased urinary frequency or worsening stress urinary incontinence (SUI), with categorical yes/no response options. Linear regression was used to assess the relationship of OAB-q SF score with continuous adherence variables and logistic regression was used calculate odds ratio (OR) and confidence intervals (CI) for categorical variables. Significant relationships were further evaluated with multivariate regression. Potential confounding variables included in the multivariate model were identified by using χ2 and t test to assess demographic differences between adherent and non-adherent groups.
4,029 participants were contacted, and 280 surveys were completed (6.9% response rate). Mean age was 61 years old, 70.4% were female, mean BMI was 32.5 kg/m2, and mean OAB-q SF score was 22.2%. The majority of participants were taking the diuretic for hypertension (57%). Twenty-four percent were taking a loop diuretic and 55.4% reported experiencing SUI (table 1). Of the entire cohort, 54 participants (19.3%) admitted skipping diuretic doses due to increased LUTS (33 due to increased urinary frequency, 3 due to worsening SUI, 18 due to both).
Linear regression of OAB-q SF versus the two validated adherence measures produced best fit lines with positive slopes, indicating direct relationship between LUTS severity and diuretic non-adherence. However, R-coefficients were low (0.012 and 0.002). Logistic regression showed increasing OAB-q SF score was significantly associated with skipping diuretic doses due to increased urinary frequency (OR 1.029; 95% CI, 1.014-1.044, P<0.001) and worsening SUI (OR, 1.069; 95% CI, 1.046-1.096; P<0.001; table 2). After controlling for BMI, smoking status, and education, OAB-q SF score remained significantly associated with skipping doses due to increased urinary frequency (OR, 1.028; 95% CI, 1.012-1.044; P<0.001) and worsening SUI in multivariate analysis (OR 1.069; 95% CI 1.045-1.099; P<0.001; table 2).
Interpretation of results
For every additional point in OAB-q SF score, we found a 2.8% increase in odds of participants skipping diuretic doses due to increased urinary frequency and a 6.9% increase in odds of skipping diuretic doses due to worsening stress urinary incontinence.