Does the index-to-ring finger length ratio (2D:4D) differ in amyotrophic lateral sclerosis (ALS)? Results from an international online case–control study

Affiliates Jane A. Parkin Kullmann [1], Roger Pamphlett [1]


[1] Discipline of Pathology, Sydney Medical School, Brain and Mind Centre, The University of Sydney

Journal BMJ Open
Summary Literature has indicated an association between a lower ratio of the length of the index finger (2D) to the ring finger (4D) (2D:4D) and developing ALS. This led to the suggestion that increased prenatal exposure to testosterone, which also lowers the 2D:4D ratio, could be a risk factor for ALS. This case control enlisted 202 patients with ALS and 370 non-ALS controls. While males had significantly lower mean 2D:4D ratio than females, regardless of ALS status, there were no detectable differences between ALS and control groups.
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