Present day insights into the relationship between gender and health emphasise the necessity of taking sex and gender differences into consideration. Sex refers to biological characteristics such as chromosomes, physiology and anatomy that distinguish females and males. Gender refers to the array of socially constructed roles and relationships, personality traits, attitudes, behaviours and values that society ascribes to the two sexes on a differential basis. In health-related research both sex differences and differences resulting from gender are implied. Sex can determine differential propen.