The Relationship between 2D:4D Digit Ratio and Lung Function

Abstract

Background: Sex hormones have an important role in many physiological processes, including lung maturation. It has been suggested there is a direct link between prenatal sex hormone exposure and lung physiology and function. The 2D:4D digit ratio (DR) is a proxy marker for determining an individual's hormone exposure prenatally. The DR is a sexually dimorphic trait, with males tending to have a lower DR than females. Therefore, it has been hypothesized that DR may be related to lung function. Objectives: To investigate if there is a relationship between DR and lung function by measuring the pulmonary function and digit ratio of each participant. Comparisons between the total population's actual pulmonary function measurements and predicted results were made along with male versus female and non-smoker versus smoker comparisons. Methods: 65 healthy participants with no report of cardiovascular or respiratory problems were enrolled in the study. Prior to the lung function tests, the lengths of the 2nd and 4th digits of the right hand were measured using a digital caliper. The pulmonary lung function tests were carried out on a Vitalograph Alpha Spirometer. 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 DR and any of the four LFTs from the total population (n=65), females alone (n=44), non-smokers alone (n=58) and smokers alone (n=7). One significant positive correlation was observed between DR and actual FEV1 in males alone (FEV1: R= 0.458, P=0.037), however there was no significant correlation between DR and the other three pulmonary function actual tests. 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 (LFTs) and had lower DR however this was not significantly different from females (M: 0.99±0.04 vs. F: 1.00±0.03, P=0.416). Overall the total population significantly underperformed. Conclusion: From the analysis of the results it was discovered digit ratio was not related to lung function. However, this study also showed small inconsistencies regarding this statement. To further understand the true nature of DR a large scale study with varying ages, health conditions and smoking status would need to be carried out. Other factors such as genetic, exercise, smoking status, weight and environment may have a stronger influence on lung function. Keywords: Digit Ratio; Lung Function; Sex Hormones.