Study Links Colour Vision Deficiency to Lower Bladder Cancer Survival

A new study published in Nature Health suggests that patients with colour vision deficiency who develop bladder cancer have lower survival rates than those without the visual condition. The findings raise concerns that difficulties in detecting blood in urine, a key early symptom, may delay diagnosis and treatment.

Researchers analysed electronic medical records from 2004 to 2025, comparing 135 patients diagnosed with both bladder cancer and colour vision deficiency with a matched group of 135 bladder cancer patients without visual impairment. The analysis found higher long-term mortality among patients with colour vision deficiency.

Bladder cancer often begins with painless haematuria, or visible blood in the urine, which typically prompts patients to seek medical advice. The authors suggest that individuals who have difficulty perceiving red hues may not notice this warning sign, leading to later medical consultation and potentially more advanced disease at diagnosis.

Notably, the study did not observe the same effect in colorectal cancer patients with colour vision deficiency. Researchers attribute this difference to the availability of screening programmes and additional symptoms in colorectal cancer, such as abdominal pain or changes in bowel habits, which reduce reliance on visual detection alone.

The study is based on data from the TriNetX database, which contains anonymised records from millions of patients worldwide. While the authors consider the data robust, they caution that the retrospective design limits conclusions to associations rather than direct causation. Underdiagnosis of colour vision deficiency may also affect the results.

Clinically, the findings do not call for immediate changes to bladder cancer screening guidelines. However, experts say they highlight the need for greater awareness among healthcare providers and patients. For individuals at higher risk of bladder cancer, recognising sensory limitations could help support earlier detection and improved outcomes.