Second-to-fourth digit ratio and age predicting the severity of androgenetic alopecia: a cross-sectional study

Abstract

Purpose: Androgenetic alopecia (AGA) is a common type of hair loss. Previous studies indicated that the relative length of the index and ring finger (2D:4D ratio) of AGA patients was lower than control. However, the correlation between 2D:4D ratio and disease severity is unclear. In this study, we sought to evaluate the relationship between digit ratio of the right hand and AGA severity in male patients. Materials and methods: The cross-sectional study was performed. Hamilton–Norwood scale was used to assess severity. The finger lengths of the right hand were measured using a digital caliper. Results: Our study found that the lower the right-handed 2D:4D ratio, the greater the risk of developing AGA and that the severity of AGA increases with age. Patients with moderate and severe AGA (grade 3 and above) had lower 2D:4D ratios and higher average age compared with patients with mild AGA (Norwood grade 2). Patients aged ≥37.5 with a 2D:4D ratio <0.947 were six times more likely to have moderate-to-severe androgenetic alopecia compared with the reference group (OR: 6.11; 95% CI: 1.96–19.04). Conclusions: Combining 2D:4D ratio and older age may help predict the severity risk of AGA, and offer a clinically accessible, non-invasive approach for patients to easily predict their future severity.