Colorblindness Linked to Higher Bladder Cancer Mortality Risk

For many, the first sign of bladder cancer is a visible one: blood in the urine. But a recent study from Stanford Medicine suggests that this crucial early warning may be obscured for the roughly 8% of men and 0.5% of women who experience colorblindness, also known as color vision deficiency. Researchers have found a concerning link between this common condition and a significantly higher mortality rate among those diagnosed with bladder cancer. The study, published in Nature Health, reveals that bladder cancer patients with colorblindness faced a 52% higher risk of death over a 20-year period compared to patients with normal vision. The findings underscore the importance of awareness, not only for individuals with colorblindness but also for healthcare providers.

The Challenge of Detecting a Silent Signal

The difficulty lies in the way colorblindness affects perception. Most common forms of the condition build it hard to distinguish between red and green hues. Since blood in urine often presents as a reddish tint, individuals with colorblindness may simply not notice it. This delay in recognizing a key symptom can lead to a later diagnosis, when the cancer has potentially spread and becomes more difficult to treat. Researchers believe this delayed detection is the primary driver behind the increased mortality risk.

“If you don’t trust yourself to know that there’s a change in the color of your urine, it could be worth having a partner or somebody you live with periodically checking it for blood, just to make sure,” said Ehsan Rahimy, MD, adjunct clinical associate professor of ophthalmology and senior author of the study.

Digging Deeper: The Study and Its Scope

The Stanford team, led by Mustafa Fattah, a medical student at Columbia University, analyzed data from the TriNetX platform, a global network of electronic health records containing information on approximately 275 million patients. The analysis focused on roughly 100 million U.S. Patient records, identifying 135 individuals diagnosed with both colorblindness and bladder cancer, and 187 with both colorblindness and colorectal cancer. Each group was matched with a control group of patients with the same cancer but with normal vision.

While the link between colorblindness and increased mortality was clear for bladder cancer, the study revealed a different pattern for colorectal cancer. No statistically significant difference in survival rates was observed between patients with and without colorblindness in the colorectal cancer group. Researchers hypothesize this difference may be due to the broader range of symptoms typically associated with colorectal cancer, where blood in stool isn’t always the primary or most noticeable sign.

Beyond Blood: Why Early Detection Matters

Bladder cancer is more prevalent in men, affecting them roughly four times more often than women. In 2025, an estimated 85,000 Americans received a diagnosis. Early detection is critical for improving outcomes. The five-year survival rate for bladder cancer diagnosed at a localized stage is approximately 92%, but this drops significantly to 35% when the cancer has metastasized (spread to distant parts of the body).

This isn’t the first time researchers have explored the potential impact of colorblindness on disease detection. Earlier studies, including a 2001 experiment, demonstrated that individuals with color vision deficiency were less accurate than those with normal vision in identifying blood in samples of bodily fluids. A 2009 study also found that bladder cancer patients with colorblindness were often diagnosed at more advanced stages.

Understanding the Limitations and What the Study Doesn’t Show

It’s important to note that this study demonstrates a correlation, not causation. While the findings strongly suggest that colorblindness may contribute to delayed diagnosis and poorer outcomes in bladder cancer, it doesn’t definitively prove that colorblindness *causes* the increased mortality risk. Other factors, such as socioeconomic status, access to healthcare, and lifestyle choices, could also play a role.

the study relied on diagnostic codes recorded in electronic health records. Many individuals with colorblindness may be undiagnosed, meaning they would be incorrectly classified as having normal vision in the database. This could underestimate the true impact of colorblindness on bladder cancer mortality.

What This Means for Public Health and Clinical Practice

The findings highlight the need for increased awareness among both patients and healthcare providers. The researchers hope this study will prompt conversations about incorporating questions about colorblindness into routine screening questionnaires. Urologists and gastroenterologists, in particular, may want to consider this factor when evaluating patients presenting with potential cancer symptoms.

The study also underscores the importance of routine health checks, including urine tests during annual physicals. For individuals with colorblindness, enlisting the help of a partner or family member to monitor for changes in urine color could be a valuable precaution.

Looking Ahead: Further Research and Surveillance

The Stanford team plans to continue investigating the relationship between colorblindness and cancer outcomes. Future research could focus on developing more sensitive diagnostic tools for individuals with color vision deficiency and exploring strategies to improve early detection rates.

This study also emphasizes the power of large-scale data analysis in identifying previously unrecognized health risks. The use of platforms like TriNetX allows researchers to uncover patterns and associations that might not be apparent in smaller, more traditional studies. Continued investment in these types of research initiatives will be crucial for advancing our understanding of complex diseases and improving patient care.