Question
Why is colour blindness less common in women?
Answer
Colour blindness is less common in women primarily due to its genetic basis. The most common form, red-green colour blindness, is an X-linked recessive disorder. This means the gene responsible for this condition is located on the X chromosome. Since men have only one X chromosome, a single recessive gene on that chromosome will result in colour blindness. Women, however, have two X chromosomes, so a recessive gene on one can be compensated by a normal gene on the other, making them less likely to be affected and more likely to be carriers instead.
Genetic Basis
X-Linked Recessive Inheritance: Colour blindness is often inherited in an X-linked recessive pattern, which explains its higher prevalence in males (who have one X chromosome) compared to females (who have two X chromosomes) (Alkhalaf and Al-Khafaji, 2022; Singh and Sharma, 2021; Lawson et al., 2024; Henry et al., 2020).
Prevalence
Higher in Males: Studies consistently show a higher prevalence of colour blindness in males compared to females. For instance, prevalence rates are around 8% in males and 0.5% in females (Singh and Sharma, 2021; Lawson et al., 2024; Henry et al., 2020).
Specific Studies: In various studies, the prevalence of colour blindness in males ranged from 3.6% to 4.87%, while in females, it was significantly lower, ranging from 0.4% to 0.64% (Alkhalaf and Al-Khafaji, 2022; Saha et al., 2021; Singh and Sharma, 2021).
Types of Colour Blindness
Red-Green Deficiency: The most common type of colour blindness is red-green deficiency, which includes protanomaly and deuteranomaly. These are more prevalent in males due to the X-linked inheritance pattern (Alkhalaf and Al-Khafaji, 2022; Saha et al., 2021; Henry et al., 2020).
The lower incidence of colour blindness in women is primarily due to the X-linked recessive inheritance pattern of the condition. Women are less likely to be affected because they have two X chromosomes, allowing a normal gene on one to compensate for a defective gene on the other. This genetic mechanism results in a significantly higher prevalence of colour blindness in males compared to females.
References
Alkhalaf, A., & Al-Khafaji, R., 2022. Prevalence And Allele Frequency Of Colour Blindness In Al-Najaf Al Ashraf Province. Medical Science Journal for Advance Research. https://doi.org/10.46966/msjar.v3i2.43
Saha, R., Sarkar, I., Chatterjee, T., Samaddar, S., & Sen, S., 2021. A Hospital-Based Cross-Sectional Study to Estimate the Prevalence and Sex Distribution of Colour Vision Deficiency among School Going Children Attending a Tertiary Eye Care Centre in Kolkata City, West Bengal, India. Journal of Evidence Based Medicine and Healthcare. https://doi.org/10.18410/jebmh/2021/541
Singh, A., & Sharma, V., 2021. Commentary: Significance of early screening for colour vision in children. Indian Journal of Ophthalmology, 69, pp. 2026 – 2026. https://doi.org/10.4103/ijo.IJO_648_21
Lawson, E., Khan, A., Wessels, Q., & Taylor, A., 2024. Congenital colour vision deficiency in healthcare professionals: a scoping review protocol of the impact on clinical practice and patient safety. BMJ Open, 15. https://doi.org/10.37766/inplasy2024.11.0099
Henry, N., Stephenson, C., Clough, R., & Shea, S., 2020. Addressing and Overcoming Difficulties for Students with Colour Vision Differences or Deficits (Colour Blindness) in Educational Instruction and Assessment. The FASEB Journal, 34. https://doi.org/10.1096/fasebj.2020.34.s1.00350
