Millions of people around the world take aspirin every day. Some use it to relieve pain, while others take low-dose aspirin to reduce the risk of heart attacks and strokes.
Although aspirin has been used for more than a century, scientists are still discovering new ways it may influence health.
A new study from researchers in Denmark has found evidence that aspirin may help uncover hidden cases of bladder cancer by making existing bleeding easier to detect.
The findings, published in the Journal of Internal Medicine, suggest that doctors should pay close attention to urinary symptoms in people who have recently started aspirin treatment.
Bladder cancer develops in the tissues lining the inside of the bladder. It is among the most common cancers of the urinary tract. Smoking is one of the biggest risk factors, but age, exposure to certain chemicals, and chronic bladder irritation can also increase risk.
One reason bladder cancer can be dangerous is that it may remain unnoticed for long periods. Early tumors often cause few symptoms.
The most common warning sign is blood in the urine, but the amount may be so small that people do not notice it. Without symptoms, some cancers continue growing until they become more advanced and harder to treat.
Aspirin works by reducing the ability of platelets to stick together and form blood clots. This effect is helpful in preventing blocked blood vessels that can cause heart attacks and strokes. At the same time, it can increase the likelihood of minor bleeding becoming visible.
Researchers wondered whether this side effect might actually help reveal hidden bladder cancers. If a small tumor is already causing slight bleeding, aspirin could make that bleeding more noticeable, prompting medical evaluation.
To explore this possibility, investigators analyzed healthcare data from 50,771 adults who started taking aspirin between 2005 and 2023. They also examined data from 156,191 people who started taking non-aspirin NSAIDs. These medications are commonly used for pain and inflammation but generally have weaker antiplatelet effects than aspirin.
The researchers then compared both groups with individuals who had never used aspirin or NSAIDs.
A key focus of the study was cystoscopy. This procedure allows doctors to examine the bladder using a thin camera-equipped instrument. Cystoscopy is one of the most important tools for diagnosing bladder cancer because it enables physicians to directly view suspicious growths.
The study found that people who recently started aspirin were more likely to undergo cystoscopy than non-users. Importantly, these examinations often identified bladder cancers before they became invasive.
Although the overall prevalence of bladder cancer among aspirin users was similar to that of non-users, cancers detected in aspirin users were less likely to have reached invasive stages. This suggests that aspirin may help bring tumors to medical attention earlier in their development.
The findings for NSAID users were different. While these individuals also received more cystoscopies, they were actually less likely to have bladder cancer detected after testing. Their cancers, when present, showed a stage distribution similar to that of people who had never taken these drugs.
Researchers believe the results support the idea that aspirin may expose otherwise silent bladder tumors by making bleeding more apparent. This could encourage earlier diagnosis and potentially improve outcomes for some patients.
Lead researcher Dr. Malene Söth Hansen noted that the findings reinforce the importance of investigating suspicious urinary symptoms in people who begin aspirin therapy. The results may also have implications for studies examining whether aspirin influences bladder cancer risk.
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Source: Aarhus University.
