The 2nd-4th digit ratio (2D: 4D) and neck circumference: implications for risk factors in coronary heart disease

Background: The ratio of the lengths of the 2nd and 4th digit (2D:4D) is negatively related to prenatal and adult concentrations of testosterone (T). Testosterone appears to be a protective against myocardial infarction (MI) in men as men with low 2D:4D are older at first MI than men with high 2D:4D, and men with coronary artery disease have lower T levels than men with normal angiograms. Neck circumference (NC), a simple and time-saving screening measure to identify obesity is reported to be positively correlated with the factors of the metabolic syndrome, a complex breakdown of normal physiology characterized by obesity, insulin resistance, hyperlipidemia, and hypertension, and is therefore likely to increase the risk of coronary heart disease (CHD). Objective: To investigate possible associations between 2D:4D ratios and NC in men and women. Research methods and procedures: 2D:4D ratios, NC, along with measures of waist and hip circumferences, body mass index (BMI), and waist-to-hip ratio was recorded from 127 men and 117 women. Results: A significant positive correlation between 2D:4D and NC and was found for men but not for women after controlling for body mass index (BMI); the higher the ratio the higher the NC. Discussion: This finding supports the suggestion of NC to serve as a predictor for increased risk for CHD as previously suggested. In addition, the present association suggests a predisposition for men towards CHD via 2D:4D as proxy to early sex-steroid exposure.