The Relation Among Second To Fourth Digit Ratio, Personality Traits And Migraine

Background and objective:Migraine and Tension-type headache (TTH) are common and disabling primary headache disorders. Both show significant sex-related differences in incidence and prevalence and they are more prevalent in females. Sex hormones may have been implicated in the common pathophysiology. The second to fourth digit ratio (2D:4D) is sexually dimorphic in humans and is considered to be a negative correlate of fetal testosterone (FT) and a positive correlate of fetal estrogen (FE) and changes little with subsequent growth.2D:4D is considered to be an indicator of FT and FE. It is difficult to measure FT and FE of humans directly because of ethical constraints, our study will safely and conveniently compare the relationship between fetal sex hormones and primary headache by means of 2D:4D.Methods:Patients, who were diagnosed as primary headache at the International Headache Center of Chinese PLA General Hospital, were enrolled in the study. We selected randomly matched healthy people from many came to the medical center of our hospital for routine medical checks as controls. A total of 891 individuals (303 males,588 females) of 18-68 years in age (a mean of 37.0±10.1 years), including 279 migraine,300 TTH, and 312 healthy subjects were enrolled. A photograph of both hands was taken using a digital camera and the lengths of the fingers were measured by a single investigator using a digital Vernier caliper. The length of the index finger was divided by the length of the ring finger to obtain the 2D:4D ratio.Results:(1) Females in the migraine group had lower 2D:4D ratios in both hands than those in the control group (left hand:0.947±0.034 vs.0.955±0.038, p=0.048; right hand:0.952±0.035 vs.0.965±0.037, p=0.001). There was a similar relationship between the TTH group and the control group (left hand:0.946±0.034 vs.0.955±0.038, p=0.034; right hand:0.954±0.035 vs.0.965±0.037, p=0.005), although this was not observed in males. (2) Males showed lower 2D:4D ratios than females for the right hand in the control group (0.954±0.039 vs.0.965±0.037, p=0.015). No significant difference was found in the left hand.Conclusions:The 2D:4D ratio is a risk factor of migraine and TTH and that the balance of fetal estrogen and testosterone in utero may impact adult primary headache disorders.