Introduction to standardisation (cont.)

Age as a confounder

This shows us that the age-specific rates for Ecuador are higher than for Sweden within each age group. The crude death rate is higher for Sweden because Sweden has a greater proportion of older people, and older people have higher death rates than younger people.

We can think of this as an example of confounding.

Confounding arises from the situation where an association between an exposure and an outcome is entirely or partially due to another exposure (called the confounder).

Mortality varies greatly with age and age structure differs between populations and changes over time. Therefore, age is almost certain to confound comparisons of the death rates for different populations or points of time.

Exercise

Interaction Can you fill in the gaps in the sentence below?

In this example,
is acting as a confounding factor in the association between the exposure of interest
and the outcome
.
That's correct, age is the confounder here.
No, that is not the confounder in this case.
That's right - the country or region is the exposure of interest in this case.
No, that is not the exposure in this example.
Correct, the outcome for this example is the mortality rate.
No, that is not the outcome in this example.

Reveal answer

In this example, age is acting as a confounding factor in the association between the exposure of interest region and the outcome mortality rate.