Delayed Cancer Detection and Higher Mortality in Daltonism
- Recognizing the sight of blood in urine, the most common first sign of bladder cancer, is often the impetus that leads people too a diagnosis.But for those with...
- A study by researchers and collaborators at Stanford Medicine revealed that missing this early sign can have serious health consequences.
- the findings suggest that people with colorblindness are more likely to delay seeking care for bladder cancer because they don't recognize blood in their urine, and catching the...
Recognizing the sight of blood in urine, the most common first sign of bladder cancer, is often the impetus that leads people too a diagnosis.But for those with colorblindness, who generally struggle to see red, this warning sign is more likely to go unnoticed in the toilet.
A study by researchers and collaborators at Stanford Medicine revealed that missing this early sign can have serious health consequences. In an analysis of health records, they found that people with bladder cancer who are also colorblind have a 52% higher 20-year mortality rate than people with bladder cancer and normal vision.
the findings suggest that people with colorblindness are more likely to delay seeking care for bladder cancer because they don’t recognize blood in their urine, and catching the cancer at later stages leads to worse outcomes.
“I hope this study will raise awareness, not only for colorblind patients, but also for our colleagues who see these patients,” said Ehsan Rahimy, MD, clinical assistant professor of ophthalmology and lead author of the study published Jan. 15 in Nature Health.
The lead author of the study is Mustafa Fattah, a medical student at Columbia University’s College of Physicians and Surgeons.
not seeing red
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Colorblindness – also known as color vision deficiency – is more common than people think, affecting about 1 in 12 men and 1 in 200 women. The most common forms make it tough to distinguish between red and green, presenting daily challenges such as deciphering traffic lights, matching outfits, and judging the doneness of meat.
Bladder cancer is also more common in men,affecting about four times as many men as women. In 2025, an estimated 85,000 Americans will be diagnosed with bladder cancer.
Previous case reports and small studies have hinted that colorblindness might delay diagnosis of diseases such as colorectal cancer and bladder cancer
Color Blindness Doesn’t Impact Melanoma Survival, Study Finds
People with color blindness do not experience a difference in melanoma survival rates compared to those with normal color vision, according to a study published January 25, 2026, in the journal JAMA Dermatology. Researchers at the University of Pennsylvania investigated whether difficulty distinguishing red shades - frequently enough associated with melanoma – would affect early detection and treatment outcomes.
Background on the Research
The study built upon previous research suggesting a link between color vision deficiency and delayed diagnosis of melanoma. “We wanted to see if this translated into a survival disadvantage,” said Dr. Iman Rahimy,lead author of the study and a dermatologist at the University of Pennsylvania.
No Impact on Colorectal Cancer
Researchers anticipated a similar effect in individuals with colorectal cancer, but found no statistically significant difference in survival rates between those with and without color blindness.
Colorectal cancer often presents with different early symptoms, according to Rahimy. ”Blood in the stool is not the primary or most common symptom these patients present with.”
A study on colorectal cancer revealed that nearly two-thirds of patients initially complain of abdominal pain, and over half notice a change in their bowel habits.