Sex and hand differences in circadian wrist activity are independent from sex and hand differences in 2D:4D

Camille Reuter,Denise B Mcquade

doi:10.1186/1740-3391-7-13

Abstract

BackgroundWe investigated the relationship between patterns of sex and hand differences in circadian wrist activity and digit ratio, a marker for prenatal androgen exposure. If the contribution of prenatal androgen exposure to sex differences in digit ratio underlies sex differences in circadian wrist activity, we predict that patterns of wrist activity will be correlated with digit ratio.MethodsBilateral wrist activity of male and female college students was measured for three consecutive days. Digit ratio was obtained from photocopy measurements of the second and fourth fingers of each subject.ResultsMales had lower digit ratios with more pronounced differences on the right hand. Female acrophase occurred earlier than male acrophase. There was more activity in the right hand and right hand activity peaked before the left. Digit ratio was not correlated with any measure of wrist activity. An analysis of activity by age revealed that younger female students exhibited more male-like activity patterns.ConclusionSex and hand differences for digit ratio and acrophase replicated previous findings. The lack of correlation between digit ratio and patterns of wrist activity suggests that sexually dimorphic circadian activity develops independently from the mechanisms of hormone exposure that cause sex differences in digit ratio.

Highlights

We investigated the relationship between patterns of sex and hand differences in circadian wrist activity and digit ratio, a marker for prenatal androgen exposure
Digit Ratio Significant sex differences were found with males having lower 2D:4D than females (Table 1)
Circadian Wrist Activity and Activity Preferences No sex differences were seen in mean activity, amount of right hand or left hand activity, or asymmetry of hand activity

Summary

Introduction

We investigated the relationship between patterns of sex and hand differences in circadian wrist activity and digit ratio, a marker for prenatal androgen exposure. Each SCN comprises its own oscillator [2,3], but the two structures are thought to work in tandem to generate a single rhythm. When both sides of the body are monitored simultaneously (such as with wrist actigraphy), the rhythms for each side vary slightly [2] and the activity of the dominant hand has been shown to peak before the non-dominant hand [2,4]. The primary goal of the (page number not for citation purposes)

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Discussion

Conclusion