The Link between 2D:4D Ratio and Respiratory Function Parameters.

Abstract

Prenatal exposure to sex hormones can influence the length of an individual's second and fourth digit (2D:4D ratio). These same sex hormones may also influence physiological processes, such as respiratory function. Consequently, digit ratio could indirectly determine respiratory performance. The premise is that a lower 2D:4D ratio leads to poorer lung function. The aim of this study was to assess the positive relationship between 2D:4D ratio and respiratory function parameters. Furthermore, sexual dimorphism in this relationship was investigated. There were a total of 40 participants analysed in this study (15 males and 25 females), aged between 19-31 years old. Firstly, digital calipers were used to measure the length of each participant's second and fourth digit, and height was measured. Then, lung function tests were carried out using a Vitalograph Compact II. The statistical tests used in this study include paired t-tests, independent t-tests and Pearson's correlations. In general, weak negative correlations were found between digit ratio and lung function (actual VC and FVC: r= 0.24; FEV1: r=0.20; FEV1/FVC: r=0.07). These were all non-significant. When gender was compared, the 2D:4D ratio in males was lower than in females, but this was also non-significant (0.99 ± 0.001 vs 1.00 ± 0.0001). However, the actual respiratory values for males were significantly higher (VC: 4.52 ± 1.04 vs 3.30 ± 0.43; FVC: 4.93 ± 0.74 vs 3.50 ±0.37; FEV1: 4.00 ± 0.52 vs 2.98 ± 0.38, p<0.001). No significant relationship was observed when digit ratio and lung function were correlated in males and females separately. Despite the non-significance, a weak positive correlation between 2D:4D ratio and actual FEV1/FVC in males was found (r=0.20) To summarize, no significant positive relationship between digit ratio and lung function was uncovered. Moreover, the relationship observed does not coincide with current literature. Even when gender was analysed separately, no significant relationship was found. Despite this, since a positive correlation was found in males, this highlights that the 2D:4D ratio may be a more useful indicator of lung function in the male population. Keywords: Sex hormones; 2D:4D ratio; lung function; sexual dimorphism