Handedness in blood donors: no association with blood group or twinning.

There has been considerable interest in the contribution of inheritance to determination of handedness and in observed associations between hand laterality and twinning, gender and age. Unpublished data from a study of children born preterm suggested an association between AB0 blood group and handedness. A questionnaire filled in by 3815 blood donors, gave information on blood group, age, gender, whether they were a twin, hand used for writing and perceived handedness. There was no association between AB0 blood group or rhesus group and handedness. Significantly more females than males considered themselves right handed (82.5% versus 79.9%) and more subjects aged 50+ wrote with the right hand (90.6% versus 87.6% if younger). Twins did not differ from other subjects in this study and we hypothesise that the generally inconsistent findings relating to twins may be explained by population differences in the proportion of twins born preterm.