Color Blindness Linked to Increased Bladder Cancer Mortality Risk: Study
USA: A retrospective cohort study found that people with color vision deficiency may have a higher risk of mortality from bladder cancer, possibly due to difficulty detecting blood in urine and delayed diagnosis. No survival difference was observed for colorectal cancer, suggesting the risk is specific to cancers where visual detection of blood is crucial for early identification.
These findings were reported in Nature Health by Mustafa Fattah from Columbia University Vagelos College of Physicians & Surgeons, New York City, and colleagues. The study examined whether color vision deficiency (CVD), a common but often underdiagnosed condition, affects survival outcomes in cancers where early warning signs depend on recognizing blood in bodily waste.
Using the TriNetX electronic health records research network, the investigators conducted a retrospective analysis comparing patients with bladder or colorectal cancer who had CVD with matched patients without CVD.
Key Findings:
- Patients with bladder cancer and color vision deficiency had significantly shorter overall survival compared with matched patients without color vision deficiency.
- The analysis showed a higher long-term mortality risk among bladder cancer patients with color vision deficiency.
- These findings suggest that impaired color vision may negatively influence outcomes in bladder cancer.
- No significant survival difference was observed between patients with colorectal cancer and color vision deficiency and matched controls without color vision deficiency.
- Survival outcomes in colorectal cancer were similar regardless of color vision status.
- The contrasting results indicate that the impact of color vision deficiency on cancer survival may be specific to certain cancers rather than broadly applicable.
The authors suggest that differences in symptom presentation may explain the findings. Bladder cancer typically presents with painless visible blood in the urine, making early detection highly dependent on the patient recognizing a color change. In contrast, colorectal cancer often causes additional symptoms such as abdominal pain, altered bowel habits, weight loss, or anemia, which can prompt evaluation even if blood in the stool is not noticed. Routine colorectal cancer screening may further limit diagnostic delays, while no similar screening exists for asymptomatic bladder cancer.
Earlier case reports and observational studies support this explanation, showing that people with color vision deficiency may delay seeking care until blood is noticed by others, often presenting with more advanced disease. The current study adds population-level evidence that such delays may contribute to poorer survival in bladder cancer.
The authors noted several limitations, including reliance on diagnostic coding, possible underdiagnosis of color vision deficiency, small sample sizes, and limited cancer staging data, which may have reduced statistical power and underestimated effect sizes.
Despite these constraints, the study highlights color vision deficiency as a potential overlooked risk factor in cancer detection. The authors recommend heightened clinical vigilance for bladder cancer in patients with known or suspected color vision deficiency and call for prospective studies to determine whether targeted screening or earlier evaluation could improve outcomes in this high-risk group.
Reference:
Fattah, M., Alsoudi, A. F., Mruthyunjaya, P., & Rahimy, E. (2025). Impact of colour vision deficiency on bladder and colorectal cancer survival. Nature Health, 1(1), 113-119. https://doi.org/10.1038/s44360-025-00032-7
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