Repeat: The researchers analysed surveys completed by 2,355 twins (comprising responses from 612 full pairs) in March 2015 between the ages of 18 and 80 - most of whom were middle aged.
The researchers analysed surveys completed by 2,355 twins (comprising responses from 612 full pairs) in March 2015 between the ages of 18 and 80 - most of whom were middle aged.