The relationship between digit ratio and circadian typology among medical students

Işman Ç., Gülen Ş., Gündoǧan N.

Trakya Universitesi Tip Fakultesi Dergisi, vol.27, no.1, pp.68-73, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 27 Issue: 1
  • Publication Date: 2010
  • Journal Name: Trakya Universitesi Tip Fakultesi Dergisi
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, TR DİZİN (ULAKBİM)
  • Page Numbers: pp.68-73
  • Keywords: Circadian typology, Digit ratio, Fetal testosterone, Gender
  • Lokman Hekim University Affiliated: No


Objectives: Morningness-eveningness preference stands for interindividual chronobiological differences. This study was designed to investigate if prenatal testosterone exposure is a candidate for having a causal role in sexual dimorphism observed in circadian typology. Materials and Methods: A total of 183 students (111 females, 72 males; mean age 20.7 years) were involved in the study. Circadian typology was assessed using the Horne-Ostberg Morningness-Eveningness Questionnaire. Digit lenghts were measured with digital calipers and digit ratio (2D/4D) was calculated by dividing the length of the second digit by that of the fourth digit. Results: Circadian typology assessment revealed 54 morning-(29.5%), 100 intermediate-(54.6%) and 29 evening-(15.8%) type students. Digit ratio of both hands in males were significantly lower than females (p<0.001). Digit ratio for both hands in morningness trait were significantly higher than intermediate (p<0.001) and eveningness (p<0.05 for the left and p<0.01 for the right hand) traits. Morning type was more common among females (35.1% vs 20.8%; p<0.05). Higher digit ratio was significantly associated with the morning type for both of the hands in both genders. Conclusion: Prenatal testosterone exposure, represented by digit ratio (2D/4D) as a proxy marker, seems to have a causal role in sexual dimorphism observed in the circadian typology preferences. © Medical Journal of Trakya University. Published by Ekin Medical Publishing. All rights reserved.