(NEXSTAR) – The earliest symptoms of bladder cancer may go unnoticed by patients with colorblindness or similar color vision deficiencies, a study published in the peer-reviewed journal Nature suggests.
The study, authored by researchers and ophthalmologists at Stanford, Columbia and Beaumont University Hospital in Michigan, found that patients with colorblindness are more likely to miss a major warning sign of bladder cancer — blood in the urine — than those with normal vision.
“The findings suggest that people with colorblindness are more likely to delay seeking care for bladder cancer because they fail to recognize blood in their urine, and that catching the cancer at later stages leads to worse outcomes,” reads a press release from Stanford Medicine.
Previous studies on the link between colorblindness and bladder or colorectal cancer had suggested a link between vision deficiencies and the ability to recognize blood in saliva, urine or stool samples, researchers acknowledged. But using a tool known as TriNetX, which reportedly provided them with access to about 100 million anonymous health records from U.S. patients, the authors of the Nature study were able to narrow down a group of subjects who were diagnosed with both colorblindness and bladder or colorectal cancers, as well as their survival rates.
When comparing this subject group to patients who were diagnosed with bladder cancer, but not colorblindness, the researchers observed a stark connection, but not an entirely unexpected one, they said: Cancer patients “who were colorblind indeed had lower survival probability than those with normal vision,” the study found.
“Over 20 years, those who were colorblind had a 52% higher overall mortality risk” from any cause, the researchers added.
The same couldn’t be said for colorblind people diagnosed with colorectal cancer. As noted by the study’s authors, colorectal cancer presents several early warning (i.e., pain or changes in bowel movements) that have nothing to do with blood in the stool. Also, as noted by the Centers for Disease Control and Prevention (CDC), the U.S. Preventive Services Task Force recommends colorectal cancer screenings at “regular intervals” for adults over 45, meaning a doctor may be able to detect early signs that a patient might otherwise miss.
“Screening tests can find precancerous polyps, so that they can be removed before they turn into cancer,” the CDC writes.
Some form of colorblindness also affects roughly 8% of men and 0.5% of women, most of whom inherited the condition, according to the Colour Blindness Awareness nonprofit organization. But it can also develop as a person ages, sometimes as a side effect of medications or other conditions, like diabetes.
For these reasons and more, the authors of the study published in Nature urge patients with colorblindness to take proactive action, either by telling their doctors their concerns, or having a partner check their urine for blood. They also say some urologists are now considering asking their patients about any vision disorders during routine questionnaires.
“I’m hopeful that this study raises some awareness, not only for patients with colorblindness, but for our colleagues who see these patients,” Ehsan Rahimy, MD, the study’s senior author, said.
