A number of researchers from Stanford University School of Medicine, Columbia University, and Beaumont Hospitals in the United States have revealed remarkable results regarding an association between color blindness and bladder cancer.
The study, recently published in the journal Nature Health, showed that death rates from bladder cancer are approximately 52% higher in people with color blindness compared to patients who do not suffer from this condition.
Bladder and colon cancer
The study relied on analyzing patients’ data from their medical records stored via the TriNetX platform over a period of 20 years (2004–2025). After data refinement, 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 evaluate the impact of color blindness on the health status of these patients when they are diagnosed with these cancers, by comparing them to another group of patients with bladder or colorectal cancer, but without color blindness.
The results showed a 52% higher mortality rate from bladder cancer in patients with color blindness compared to those without. This is due to the difficulty in distinguishing one of the most important early warning symptoms, which is the presence of red blood in the urine without pain, which leads 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 that prompts the patient to seek medical care early.
Red color blindness
Color blindness, or what is known as color blindness, is one of the genetic visual problems that impairs people’s ability to distinguish some colors of the visible spectrum within certain wavelengths, specifically one of the basic colors (red, blue, green). The most common of them is poor discrimination of red and green, so their ability to perceive and distinguish these colors with somewhat weak accuracy.
Although color blindness is a genetic problem related to genes on the mother’s side specifically (carried on the
Color blindness and colorectal cancer
The study also revealed an almost noticeable effect after tracking the effect of color blindness on colorectal cancer patients when compared to those who do not suffer from color blindness, as blood in the stool appears as one of the early warning signs in the case of colorectal cancer, and despite the weak ability of color blind patients to distinguish the color of red blood coming out with the stool, the results did not show noticeable differences between the two groups.
Colorectal cancer is the second most common type of cancer that causes death globally, and the third most common. In recent years, it has been observed that its infection has increased 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 partly due to lifestyle changes, such as the increasing demand for fast food rich in processed meats, and the decreased intake of fiber found in vegetables and fruits, in addition to rising rates of obesity and lack of physical activity.
Similar symptoms and different effect
The high death rates among bladder cancer patients with color blindness was not surprising, given their difficulty distinguishing the color of red blood in the urine, which is one of the most prominent early signs of the disease, which leads to delayed diagnosis and its detection in advanced stages that are difficult to treat.
But what is striking about the results is that there is no similar effect of color blindness on colorectal cancer patients, although the appearance of blood in the stool is also a common early symptom, as is the case in bladder cancer.
After analyzing and evaluating the results, the researchers proposed a set of reasons behind this difference in impact between bladder cancer and colorectal cancer in color blind patients with similar early symptoms, summarized in the points below:
- Blood in the urine without pain is classified as the only warning sign accompanying bladder cancer, as it appears in between 80% and 90% of patients. The inability to detect it means a delay in diagnosis due to the patient’s weak ability to distinguish blood in the urine, especially since there is no pain indicative of this, so the cancer cells gain additional time, giving them the opportunity to multiply and spread before they are discovered.
- Colorectal cancer differs from bladder cancer in the number of early symptoms it has, as it is not limited to the appearance of blood in 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 in 53% of them, and weight loss was recorded in about 32%.
This diversity of symptoms gives people with color blindness a greater chance of detecting the disease early, relying on indicators that do not require visual discrimination. On the contrary, bladder cancer depends mainly on a single symptom that is often not accompanied by pain, which makes its detection more difficult in this group.
Therefore, it is necessary to participate in early and periodic detection programs for colorectal cancer, as such programs are widespread with their own intensive awareness campaigns, which may contribute to the early detection of colon cancer in color blind patients who may not know that they have this visual problem. On the other hand, this supports the hypothesis that colon cancer is linked to color blindness, as without regular examination they would not have been able to distinguish and discover the symptoms.
Recommendation for color blindness patients and doctors as well
The study came out with a clear recommendation urging people who suffer from color blindness to conduct periodic examinations to identify early any signs that may be linked to bladder cancer, which reduces the risk of worsening the disease and may save the patient from a health problem that is preparing to attack his cells and destroy them, making it difficult to treat when discovered.
It also recommended that doctors and specialists should direct color-blind patients to undergo analyzes and examinations that would reveal their condition and verify that their urinary system is free of any hidden problems that may arise without their knowledge and worsen, leading to their deterioration later.