Short Communication Second digit and fourth digit ratio – an adjunct tool to predict obstructive sleep apnea

Obstructive sleep apnea (OSA) is a sleep related breathing disorder associated with high morbidity and mortality. Digit ratio (2D:4D) a sexually dimorphic trait is a putative indicator of prenatal testosterone exposure and adult testosterone level. Present study aimed at investigating the correlation between 2D:4D ratio and OSA based on the study conducted on 290 volunteered participants of both the sexes in the age range of 20-45 years. A significant negative correlation was observed for 2D:4D with OSA related parameters specifically Berlin score, Epworth score and certain key anthropometric measurements, neck circumference (NC) and waist-hip ratio (WHR). The study thus showed that lower 2D:4D ratio, increases risk of developing OSA and hence it can be used as an adjunct tool in the prediction of OSA. Indian J Physiol Pharmacol 2014; 58(3) : 294–297 *Corresponding author : Department of Physiology, Chettinad Hospital & Research Institute, Kelambakkam, Tamil Nadu – 603 103, India (Received on January 11, 2014) also found to be higher in males than females (1, 3). It has been suggested that in males, testosterone promotes lateral growth of cheek bones, mandibles, chin, lengthening of lower facial bone (4) fat accumulation preferentially in the abdomen and more so after puberty (5). Reports also show that testosterone increases upper airway collapsibility during sleep (6). Hence assessment of testosterone may be a useful tool in identifying individuals at risk for OSA. Digit ratio (2D:4D), which is the ratio of the lengths of the index finger and ring finger is known to be determined prenatally due to exposure to testosterone (7). Men in general have low 2D:4D signifying high in utero testosterone exposure hence it can be used as a proxy marker in estimating testosterone concentration (7). Lower 2D:4D were found in active athletes (8). Masculine 2D:4D correlated with world ranking female fencers (9). Digit ratio has been Introduction Obstructive Sleep Apnea (OSA) is characterized by repeated narrowing or collapse of the upper airway dur ing s leep resu l t ing in inc reased oxygen desaturation during sleep causing arousal (1). These have been attributed to development of various co morbidities like type-2 diabetes mellitus, coronary heart disease, hypertension, renal disease, heart failure and even metabolic syndrome (1). OSA has been increasingly linked with increased Body Mass Index (BMI) , Wais t -H ip Rat io (WHR) , Neck Circumference (NC) (1, 2). Prevalence of OSA is Indian J Physiol Pharmacol 2014; 58(3) Digit Ratio and Obstructive Sleep Apnea 295 T test and continuous variables were expressed as mean±SD. Correlation analysis was done using Pearson correlation (for absolute measurements and d ig i t ra t io ) and Spearman cor re la t ion ( fo r questionnaire based measurements and digit ratio). Statistical significance between the different Berlin groups was determined by one-way analysis of var iance (ANOVA, post hoc Tukey’s mult ip le compar ison tes ts were a lso done. Leve l o f significance was set at P<0.05.