Common vision issue could lead to missed cancer warning, study finds

Colorblindness, a condition that mostly affects men, could be linked to a higher mortality risk in bladder cancer cases, a new study suggests.

About 8% of men are estimated to have a form of color vision deficiency (CVD), compared to 0.5% of women, according to global statistics.

The condition, in which patients see and identify color differently, could cause people to miss blood in their urine, which is a vital sign of bladder cancer.

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Blood in the urine is the most common first sign of the disease and is often the impetus that leads to diagnosis, according to researchers at Stanford Medicine.

Those with colorblindness usually have difficulty seeing the colors red and green, which can present "everyday challenges."

In the latest study, published in the journal Nature Health, researchers analyzed health records and found that bladder cancer patients who are also colorblind have a 52% higher mortality rate over 20 years than those patients with normal vision.

Since colorblind people fail to recognize blood in their urine, they may be delayed in seeking care, which can lead to worse outcomes, the findings suggest. Bladder cancer is about four times more common among men than women.

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Senior study author Ehsan Rahimy, M.D., adjunct clinical associate professor of ophthalmology at Stanford Medicine, commented in a press release that he's "hopeful this study raises some awareness, not only for patients with colorblindness, but for our colleagues who see these patients."

Dr. Douglas Lazzaro, a professor in NYU Langone's Department of Ophthalmology, said the inability to recognize the color red in this scenario is a "real risk."

"The patient, family and medical doctor should be made aware of this potential gap in diagnosis," Lazzaro, who was not involved in the study, told Fox News Digital. "It is important to raise awareness of potential issues in making the diagnosis of bladder or kidney cancer in colorblind individuals."

"My guess is that many doctors may not be looking closely enough at the medical record to pick up on this eye problem, leading to delays in diagnosis as the patient may not be able to see the issue," he added.

While the issue may not be completely avoidable, Lazzaro suggested that it could be prevented if colorblind patients are aware of the risk and inform their doctors of their vision limitation.

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Dr. Don Railsback, optometrist and CEO of Vision Care Direct in Kansas, agreed that people with known CVD and their clinicians should "pay close attention."

"This is the kind of small detail in a medical history that can change how we counsel patients on the symptoms they should never ignore," he told Fox News Digital.

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"The takeaway is simple: Don't rely on color alone to detect a problem. Bladder cancer can present as painless bleeding, and if you ever suspect blood in your urine, you should alert your doctor."

Railsback, who was not part of the research, added that if the color of urine looks "off" - for example, is tea-colored or unusually dark - the patient should be checked "promptly."

"This study is a strong reminder to tailor health guidance to real-world differences and variations, including color vision," he said.

For colorblind individuals, Railsback recommends asking their primary care physician for a urine test at annual visits. If something seems unusual, they should ask a spouse or partner.

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"Colorblindness doesn't cause bladder cancer, but it may make the earliest warning sign easier to miss," he said. "The fix is awareness and simple testing, not fear."

Fox News Digital reached out to the study authors for comment.