Early detection of bladder cancer is directly linked to survival, but a new study shows that for some people the path to diagnosis may be more complicated for reasons that have received little attention until now.

Scientists drew attention to the fact that one of the key early symptoms of this disease—blood in the urine—is not always easy to recognize, especially for people with color vision deficiencies.

The results of the study were published in the journal Nature Health.

Bladder cancer often develops without pain or pronounced discomfort. In its early stages, the disease may produce almost no sensations other than a change in urine color. That is why visual perception plays a crucial role. If a person has difficulty distinguishing shades of red or brown, they may simply fail to notice the warning sign or mistake it for something harmless. As a result, seeking medical care is delayed while the disease continues to progress.

The authors analyzed medical records of patients with bladder cancer and found a noticeable difference in outcomes. People with color blindness had lower survival rates than those with normal color vision.

Importantly, no such pattern was found for other types of cancer in which early symptoms depend less on visual changes. This strengthens the conclusion that difficulty recognizing blood in the urine may play a critical role.

The researchers believe these findings should influence diagnostic approaches. In their view, physicians should take individual patient characteristics into account and not rely solely on visual descriptions of symptoms. Even minor suspicions—such as changes in urine clarity, sensations of discomfort, or unexplained abnormalities in test results—may warrant further examination.