Correlation between Second and Fourth Digit Length Ratio with Height, Body Mass Index and Axial Length of Eyeball in Adult Population of Burdwan, West Bengal, India
Flat No. Q/2, Lake Gardens Government Housing, 48/4, Sultan Alam Road,
Kolkata, West Bengal, India.
Introduction: Studies are being conducted to correlate second (2D) to fourth digit (4D) length ratio as an anthropometric marker of prenatal sex steroid exposure with human body. As 2nd digit: 4th digit (2D:4D) ratio is an anthropometric window into the interplay of sex hormones in-utero, this tool may be tested to note if there is any correlation between the sexual dimorphism of axial length and the Digit length ratio.
Aim: To find a correlation between digit length ratio (2D:4D) with physical parameters like height, Body Mass Index (BMI) and axial length of eyeball in the adult population of South Bengal presenting in a tertiary care hospital, in Burdwan, West Bengal, India.
Materials and Methods: A cross-sectional study with simple random sampling was conducted on 500 patients (age =20 years) from March 2016 to February 2017 in the Departments of Anatomy and Ophthalmology Out Patients Department (OPD) of a tertiary care Hospital and Medical College in West Bengal, India. Height, weight, axial length of eyeball were measured and the BMI was computed for the study population. Statistical analysis was done with Statistical Package for Social Sciences (SPSS) version 16.0. Unpaired t-test was used for determining possible group differences in 2D:4D length ratios. Pearsonâ€™s correlation coefficients were used to find a correlation between second and fourth digit length ratio (2D:4D) with height, BMI and axial length of eyeball in the study population. The p-value <0.05 was considered significant.
Results: The study included 280 males and 220 females with a minimum age above 20 years and most of the patients belonged to the age group of 50-69 years. A 2D:4D length ratio was significantly lower in males compared to females (for Right hand t=34.91, p<0.001, and for left hand t=14.30, p<0.001). Correlation analysis of 2D:4D length ratio of right and left hands with height of males revealed significant negative correlation (Right hand: r=-0.679, p<0.001; Left hand: r=-0.0463, p<0.001). In females, the result was positively significant for both hands (Right hand: r=0.313, p<0.05; left hand: r=0.21, p<0.05). A 2D:4D length ratio and BMI of males showed significant positive correlation for both Right hand (r=0.18, p<0.05) as well as for the left hand (r=0.137 p<0.05). In case of females, however 2D:4D ratio and BMI showed weakly negative correlation for both hands but the values were not significant. Correlation of 2D:4D length ratio of right and left hands on axial length of eyeball in males revealed significant negative correlation (right hand: r=-0.706, p<0.001; left hand: r=-0.25, p<0.05) but in females, there was significant positive correlation for the right hand (r=0.145, p<0.05) and positive but non-significant correlation for the left hand at 95% CI (r=0.087, p>0.05).
Conclusion: In this study, authors have tried to establish that 2D:4D ratio (which is significantly higher in females) can be used as a putative non-invasive anthropometric marker to differentiate between males and females, which presumably is prenatally determined by in-utero sex steroid hormone exposure. By correlation studies, authors have also tried to prove that this parameter correlates well with other anthropometric measurements like height, BMI and ocular axial length which are already known to be significantly different in males and females.