A recent study published in Nature Health indicates that individuals with color vision deficiency (colorblindness) who are diagnosed with bladder cancer face a higher mortality rate over two decades compared to bladder cancer patients with normal vision. Researchers suggest this increased risk is associated with delayed diagnosis, primarily due to difficulty in recognizing blood in urine, a common early symptom.
Research Findings
The study revealed that bladder cancer patients with color vision deficiency experienced a 52% higher mortality rate over 20 years compared to those without the condition, correlating to a risk ratio of 1.52.
This increased risk is hypothesized to stem from delayed diagnosis. For 80% to 90% of bladder cancer cases, painless hematuria (blood in urine) is the sole initial symptom. Individuals with color vision deficiency may have difficulty discerning red hues, thereby missing this crucial early indicator and potentially postponing medical evaluation. A 2001 study supports this, showing colorblind participants correctly identified bloody substances only 70% of the time, compared to 99% for those with normal vision.
In contrast, the study found no statistically significant difference in survival rates for colorectal cancer patients with or without color vision deficiency. This may be attributed to several factors:
- Colorectal cancer often presents with a wider range of symptoms beyond blood in stool, including abdominal pain, changes in stool habits, or weight loss.
- Routine colorectal cancer screening is recommended for adults aged 45 and above in the United States, which can lead to earlier detection.
Methodology
Researchers from institutions including Stanford University School of Medicine, Columbia University, and Beaumont Health conducted the analysis. They utilized TriNetX, a platform that aggregates de-identified electronic health records from approximately 275 million individuals globally.
From about 100 million U.S. records, the study identified:
- 135 bladder cancer patients with color vision deficiency, who were then compared to a matched control group of patients with normal vision.
- 187 colorectal cancer patients with color vision deficiency, also compared to a matched control group.
The study acknowledged limitations, including sparse cancer staging data in the underlying records, which restricted the direct assessment of disease stage at diagnosis.
Context and Prevalence
Color vision deficiency affects approximately 1 in 12 men and 1 in 200 women. Bladder cancer is also more prevalent in men, with an estimated 85,000 Americans projected to be diagnosed in 2025. Routine color vision screening is not widespread in the U.S., meaning many adults may be unaware of their condition.
Implications and Recommendations
The findings suggest that color vision deficiency may be an under-recognized risk factor for reduced survival in bladder cancer patients. Ehsan Rahimy, MD, an adjunct clinical associate professor of ophthalmology and a senior author of the study, highlighted that some medical professionals, including urologists and gastroenterologists, have been unaware of colorblindness as a potential factor in cancer diagnosis.
The study's authors recommend increased awareness among both patients and healthcare providers regarding the potential impact of color vision deficiency on symptom recognition. For individuals with color vision deficiency, the importance of annual urine tests and potentially seeking assistance from a trusted person to periodically check for blood in urine is underscored. The research also provides a basis for future investigation into whether targeted bladder cancer screening could be beneficial for high-risk individuals with color vision deficiency.