Like variations by gender, variations by age group can also be explained by the nature of a condition or by a particular policy, such as a screening policy. Variations linked to age can therefore be categorised as unwarranted if they do not reflect these parameters. They can also be considered unwarranted if a high coefficient of variation is observed for one or several age groups, despite overall high rates for the same age groups.
Looking at the example of mammograms, current recommendations call for breast cancer screening for women aged 50 to 69. While the coefficient of variation is relatively stable in these age groups (see figure below), we can see that it is significantly higher in the 40-50 age groups. The increased coefficient of variation in these age groups probably indicates that prescribers are uncertain as to whether mammograms are advisable for women of this age category.