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

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).

To investigate possible associations between 2D:4D ratios and NC in men and women.

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.

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.

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.