2nd to 4th Digit Ratio (2D:4D) – Is It a Marker for Dyslexia ?

Abstract

Background: Specific learning disorder in general called as dyslexia is a neuro developmental disorder, which occurs more commonly in males (Male:Female ratio is 4:1), there are evidence to suggest role of prenatal gonadal hormone exposure in neurodevelopment. However, studies on association between 2nd to 4th digit ratio and dyslexia are mixed. Objective: To compare the 2nd and 4th digit ratio (2D:4D) of both hands between children with dyslexia and children without dyslexia. Methodology: A case control study, recruited 30 children with dyslexia and 30 age and education matched normal controls, after getting informed consent from their parents. Collected socio demographic details, applied CARS, Schonell's reading and spelling test, followed by detailed evaluation by psychiatrist and clinical psychologist, including psychological testing to confirm the diagnosis of dyslexia. The digit length of index and ring finger on both hands of all children were measured using Vernier Calliper by direct method. Results: In both the hands 2D:4D ratio was more in children with dyslexia than normal children, but the difference was not significant (p-0.146). Analysis of only male samples showed digit ratio is higher in dyslexic children than normal children; which were significant (p-0.03). Conclusion: Our study does not support an association between digit ratios and dyslexia; however, trend towards higher ratio in dyslexia especially in male children are interesting and needs further exploration. Need more studies in this area to form a definite conclusion.