Khaberni - A number of researchers from the College of Medicine at Stanford University, Columbia University, and Beaumont Hospitals in the United States have revealed striking results related to a connection between color blindness and bladder cancer.
The study, recently published in Nature Health, showed that mortality rates from bladder cancer are approximately 52% higher among those with color blindness compared to patients without this condition.
Bladder and Colon Cancer
The study relied on analyzing patient data from their medical records stored on the TriNetX platform over 20 years (2004–2025). After data refinement, the sample included 135 patients with bladder cancer and color blindness, and 187 patients with colon and rectal cancer and color blindness.
The study, which is a retrospective cohort study, aimed to assess the impact of color blindness on the health of these patients when diagnosed with these cancers, by comparing them with another group of patients affected by bladder or colon and rectal cancer but without color blindness.
The results showed an increase in mortality rates due to bladder cancer by 52% among patients with color blindness compared to those without. This is attributed to the difficulty of recognizing one of the most important early warning symptoms, which is the presence of blood in the urine in its red color without pain, leading to delayed attention to the condition.
As a result of this delay, the disease is often not discovered until it is in advanced stages after the cancer has developed and spread, especially since this symptom is not accompanied by pain prompting the patient to seek medical care early.
The color red and color blindness
Color blindness or color vision deficiency is a genetic visual issue that impairs the ability of individuals to distinguish certain visible spectrum colors at specific wavelengths, particularly one of the primary colors (red, blue, green), with red and green weakness being the most common, thus their ability to accurately perceive and distinguish these colors is somewhat weak.
Although color blindness is a genetically related problem from the mother's side specifically (carried on the X chromosome), it can also be acquired due to other diseases, taking certain medications, or possibly due to damage to the cornea or optic nerve among other possible causes, and it is more prevalent among males (8%) than females (0.5%), with a rate of one person out of every 12 men, and one woman out of every 200 women.
Color blindness and colon and rectal cancer
The study also revealed a nearly noticeable effect after tracking the impact of color blindness on patients with colon and rectal cancer when compared with those not affected by color blindness, as blood with stool is one of the early warning signs in cases of colon and rectal cancer, and although patients with color blindness have difficulty distinguishing the color of the red blood coming with the stool, the results did not show significant differences between the two groups.
Colon and rectal cancer is the second most cause of cancer-related deaths globally, and the third most prevalent. It has been noted in recent years an increase in incidence among younger age groups, to include people in their twenties, thirties, and forties, after it was more common among those over the age of fifty.
This shift is partially attributed to lifestyle changes, such as increased consumption of fast food rich in processed meats, lower intake of fibers found in vegetables and fruits, along with higher rates of obesity and lack of physical activity.
Similar symptoms and different impact
The higher mortality rates among bladder cancer patients with color blindness were not surprising, given their difficulty in recognizing the color of red blood in the urine, which is one of the most prominent early signs of the disease, leading to delayed diagnosis and discovery in stages difficult to treat.
However, what is noteworthy in the results is the lack of a similar effect of color blindness on patients with colon and rectal cancer, despite the appearance of blood with the stool also being an early common symptom, as is the case with bladder cancer.
After analyzing the results and evaluating them, the researchers suggested several reasons behind this difference in impact between bladder cancer and colon and rectal cancer in patients with color blindness with similar early symptoms, summarized in the points below:
- Blood in the urine without pain is classified as the only accompanying warning sign for bladder cancer, appearing in between 80% to 90% of patients, so the inability to detect it means delayed diagnosis due to the patient's weak ability to distinguish blood in the urine, especially since no pain indicates that, allowing cancer cells additional time to proliferate and spread before being discovered.
- Colon and rectal cancer differs from bladder cancer in the multiplicity of its early symptoms, as it is not limited to the appearance of blood with the stool only. According to a study published in the journal Surgery, 63% of patients suffered from abdominal pain, 54% complained of changes in the pattern of defecation, while rectal bleeding appeared for 53% of them, and weight loss was recorded for about 32%.
This variety of symptoms gives those with color blindness a greater opportunity to discover the disease early, by relying on indicators that do not require visual discrimination. Conversely, bladder cancer primarily relies on one symptom often unaccompanied by pain, making its discovery more challenging for this group.
Therefore, it is necessary to engage in early detection and regular screening programs for colon and rectal cancer, as such programs are widespread with intensive awareness campaigns, which may contribute to early detection of colon cancer in patients with color blindness who may not be aware of their visual problem. Conversely, this supports the hypothesis that links colon cancer with color blindness, as without regular screening they couldn’t recognize the symptoms and detect them.
Recommendation for patients with color blindness and doctors as well
The study concluded with a clear recommendation urging individuals with color blindness to undergo regular examinations to early recognize any signs that may be associated with bladder cancer, reducing the risk of the disease worsening and potentially saving the patient from a health problem poised to pounce on his cells and finish them off, making it difficult to treat when discovered.
It also advised doctors and specialists on the need to direct patients with color blindness to undergo tests and examinations that reveal their condition and verify that their urinary system is free from any hidden problems that arise without their knowledge and worsen to subsequently harm them.
