An Investigation of the Relationship Between 2D:4D ratio and Respiratory Function Parameters.

Abstract

Background: Sex hormones play an important role in a high number of physiological functions including lung maturation. Studies have brought forward evidence of a direct link between prenatal sexual hormones exposure and lung physiology and capacity. The 2D:4D (second digit and forth digit) ratio is also believed to be influenced by prenatal androgens exposure, and more precisely to be negatively correlated to the prenatal testosterone exposure. Digit ratio is a sexually dysmorphic trait, men have lower digit ratio than women. Therefore it had been hypothesized that there could be an existing correlation between the digit ratio of an individual and his lung function. Objectives: To investigate if there is a significant correlation between digit ratio and lung function by measuring the digit ratio and lung function of a recruited population. Comparison between the total population predicted and measured performances were made as well as between men and women, and smokers and non-smokers. If a correlation is found, discuss any clinical application it might have. Methods: 42 healthy participants with no history of respiratory problems were recruited. First of all, their height was measured thanks to a stadiometer, then their 2nd and 4th digit were measured with digital callipers and from those measures their digit ratios were calculated. Then a Vitalograph Alpha Spirometer was used to carry out pulmonary function tests. The Pearson's Linear correlation, student's paired and independent t-test statistical tests were used for analysis. Results: There was no significant correlation between digit ratio and any of the four lung function tests from the total population (n=40), females alone (n=25), males alone (n=15), non-smokers alone (n=36) and smokers alone (n=4). There were no significant correlations observed between DR and the predicted measurements from the total population, females, males, non-smokers and smokers. Males performed significantly better than females in the lung function tests, and had lower digit ratios however they were not significantly different from females digit ratio (M: 0.99±0.04 vs. F: 1.00±0.03, P=0.289). Overall the total population significantly underperformed. Discussion: Our results did not support the theory of an existing correlation between digit ratio and lung function. However other studies carried out on a larger population presented different results. Our study had some limitations, first of all the results of the pulmonary function tests were collected after the participants' first try, hence most of them probably underperformed. Furthermore, our population was restricted. To further understand the true nature of digit ratio and possibly to find out clinical application, a large scale study with varying ages, health conditions and smoking status would need to be carried out. Other factors such as age, physical activity and smoking habits might have a more important influence on lung function than prenatal androgens exposure. Keywords: 2D:4D ratio, Lung Function, Sex Hormones.