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Evaluation Video

Oral Presentation

Session: From Data to Diagnosis: Methods and Applications in Cancer Pharmacoepidemiology

Time to cystoscopy after low- or high-dose aspirin initiation: A Danish nationwide cohort study

Wednesday, August 28, 2024
9:45 AM – 10:00 AM CEST
Location: Conv Hall I D

Background: Bladder cancer ranks 10th among the most common cancers globally, and symptoms typically debut with macroscopic hematuria, prompting cystoscopic evaluation. The incidence of several cancers is reduced among aspirin users, but bladder cancer incidence seems unaffected. Aspirin is an antiplatelet agent and may cause hematuria, which may enhance the detection of early-stage bladder cancers. If so, estimates of the association between aspirin use and bladder cancer risk may be biased.


Objectives: Our objective was thus to evaluate time to cystoscopy among aspirin initiators compared to unexposed matches from the background population.


Methods: Based on the Danish health registries, we conducted a cohort study including all adult Danish first-time low-dose aspirin initiators ( < 150 mg/day), receiving more than one prescription within a four-month timeframe in 2005-2018. We chose a landmark, four months after the primary prescription, as our index date. We excluded individuals with any of the following events before the index date: high-dose aspirin-, NSAID- or other blood thinner prescriptions, cystoscopy, hospital diagnosis of hematuria, any cancers, bleeding disorders or certain predefined urological diseases usually requiring a cystoscopy. At the index date, we matched initiators 1:10 to unexposed individuals from the background population by age, sex, calendar year and municipality. We computed hazard ratios (HR) and 95% confidence intervals (CI) using cox regression analysis. Adjustment was for age, sex, calendar year and Charlson Comorbidity Index level. Assumptions were checked using log-minus-log plots.

Preliminary results: We included 51 958 low-dose aspirin initiators. Low-dose aspirin initiators were 47% female, with a median age 67 years. During the first year of follow-up, low-dose aspirin initiators underwent 9.07 cystoscopies per 1 000 person-years; 5.48 among comparisons. This corresponded to an adjusted HR of cystoscopy of 1.50 (95% CI, 1.35; 1.67).


Conclusion: Low-dose aspirin initiation was associated with a higher rate of cystoscopic procedures the subsequent year compared with unexposed individuals from the background population. The rate of cystoscopic procedures following low-dose aspirin initiation is important to account for when evaluating the association between low-dose aspirin use and bladder cancer risk.