Bernhard Fink, JT Manning, and Nick Neave (2006)

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

International Journal of Obesity, 30(4):711-714.

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
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