Khaberni - A number of researchers from the Medical Schools at Stanford University, Columbia University, and Beaumont Hospitals in the United States have revealed notable findings related to the existence of a connection between color blindness and bladder cancer.
The study, published recently in Nature Health, showed that mortality rates from bladder cancer increased by about 52% among those with color blindness compared to patients who do not suffer from this condition.
Bladder cancer and colon cancer
The study was based on analyzing patient data from their medical records stored on the TriNetX platform over 20 years (2004–2025). After refining the data, the sample included 135 patients with bladder cancer and color blindness, and 187 patients with colorectal cancer and color blindness.
The study, a retrospective cohort study, aimed to assess the impact of color blindness on the health status of these patients when diagnosed with these cancers, comparing them to another group of patients with bladder or colorectal cancer, but without color blindness.
The results showed an increase in the mortality rate due to bladder cancer by a percentage reaching 52% among patients with color blindness compared to those not affected. This is attributed to the difficulty in distinguishing 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 advanced stages after the cancer has developed and spread, especially since this symptom is not accompanied by pain that drives the patient to seek medical care early.
The color red and color blindness
The disorder of distinguishing colors, or what is known as color blindness, is one of the hereditary visual problems that impair the ability of individuals to distinguish certain visible spectrum colors within specific wavelengths, specifically one of the basic colors (red, blue, green), with red and green discrimination weakness being the most common, making their ability to perceive and distinguish these colors somewhat weak.
Although color blindness is a hereditary problem related to genes from the mother's side specifically (carried on the X chromosome), it can also be acquired due to other diseases or taking certain medications, or perhaps 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%), at a rate of one in every 12 men, and one in every 200 women.
Color blindness and colorectal cancer
The study also revealed an effect that was almost noticeable after tracking the impact of color blindness on patients with colorectal cancer compared to those not affected by color blindness. Blood appearing with feces is one of the early warning signs in the case of colorectal cancer, and despite the weak ability of color blindness patients to distinguish the red color of the blood that comes out with feces, the results did not show significant differences between the two groups.
Colorectal cancer is the second most deadly cancer worldwide, and the third most prevalent. It has been observed in recent years to acquire among younger age groups, including people in their twenties, thirties, and forties, after it was more common among those over fifty.
This shift is partly attributed to changes in lifestyle, such as an increased consumption of fast food high in processed meats, low intake of fiber found in vegetables and fruits, along with high rates of obesity and lack of physical activity.
Similar symptoms and different impact
The rise in mortality rates among patients with bladder cancer who have color blindness, due to the difficulty of identifying the red color of blood in urine, an early sign of the disease, leading to delayed diagnosis and its discovery in advanced stages that are difficult to treat, was not surprising.
However, what is significant in the results is the lack of a similar impact of color blindness on patients with colorectal cancer, although the appearance of blood with feces is also an early symptom common to both bladder cancer and colorectal cancer.
After analyzing the results and evaluating them, the researchers suggested a number of reasons behind this difference in impact between bladder cancer and colorectal cancer in patients with color blindness despite the similarity of early symptoms, summarized in the points below:
Blood in urine without pain is classified as the only warning sign accompanying bladder cancer, appearing in 80% to 90% of patients, with the inability to detect it meaning a delay in diagnosis due to the patient's poor ability to distinguish blood in the urine, especially since no pain indicates this, allowing cancer cells additional time to proliferate and spread before their detection.
Colorectal cancer differs from bladder cancer in having multiple early symptoms; it is not limited to the appearance of blood with feces only. According to a study published in the journal Surgery, 63% of patients experienced abdominal pain, 54% reported changes in bowel patterns, while rectal bleeding occurred in 53% of them, and about 32% recorded weight loss.
This variety in symptoms gives those with color blindness a greater opportunity to detect the disease early, relying on indicators that do not require visual discrimination. In contrast, bladder cancer primarily relies on a usually painless symptom, making it harder for this group to detect.
Therefore, it is essential to engage in early detection and regular programs for colorectal cancer, as such programs spread with intensive awareness campaigns, which may contribute to early detection of colorectal cancer in patients with color blindness who may not be aware of their visual impairment. Conversely, this supports the hypothesis that links colorectal cancer with color blindness, as without regular examinations, they would not have been able to recognize the symptoms and discover them.
Recommendation for patients with color blindness and doctors alike
The study concluded with a clear recommendation urging individuals who suffer from color blindness to undergo periodic examinations to detect early any signs that may be related to bladder cancer, reducing the risk of the disease worsening and potentially saving the patient from a health problem ready to prey on their cells and make treatment difficult when discovered.
Doctors and specialists are also advised to guide patients with color blindness to undergo analyses and examinations that would reveal their condition and ensure their urinary system is free from any issues that may arise unnoticed and worsen to lead them later in deterioration.
