What is the difference between confounding and effect modification?

Confounding factors are a “nuisance” and can account for all or part of an apparent association between an exposure and a disease. Confounding factors simply need to be eliminated to prevent distortion of results. Effect Modification is not a “nuisance”, it in fact provides important information.

Can you have confounding and effect modification?

Yes, it is absolutely possible that a variable is both a confounder and an effect modifier.

What is an effect modification?

Effect modification describes the situation where the magnitude of the effect of an exposure variable on an outcome variable differs depending on a third variable. In other words the presence or absence of an effect modifier changes the association of an exposure with the outcome of interest.

What is a confounding effect?

What is confounding? Confounding is often referred to as a “mixing of effects”1,2 wherein the effects of the exposure under study on a given outcome are mixed in with the effects of an additional factor (or set of factors) resulting in a distortion of the true relationship.

What is an effect modifier example?

As an example, a drug treatment effect on a particular health outcome may be stronger in males than females, in which case, gender is acting as an effect modifier. Or if we consider driving and alcohol consumption as risk factors for injury, alcohol is likely to increase the impact of driving on the risk of injury.

Is effect measure modification a bias?

Effect measure modification is not a bias or error, and it is not something that we need to avoid or adjust for. It is just an interesting observation that the measure of association differs across groups. Effect measure modification simpley means that two or more stratum-specific estimates are different.

What are examples of effect modifiers?

Is effect modification the same as moderation?

A moderator (also known as an effect modifier) is a variable for which the effect of the predictor on the outcome varies. Some moderators are also confounders, but not if they don’t cause the predictor.

What is the 10 rule for confounding?

The 10% Rule for Confounding The magnitude of confounding is the percent difference between the crude and adjusted measures of association, calculated as follows (for either a risk ratio or an odds ratio): If the % difference is 10% or greater, we conclude that there was confounding.

How do you identify effect modification?

To check for effect modification, conduct a stratified analysis. If the stratum-specific measures of association are different than each other and the crude lies between them, then it’s likely that the variable in question is acting as an effect modifier.

Can a variable be both an effect modifier and confounder?

A variable is not simply a confounder (or an effect modifier) for a treatment nor is it simply a confounder (or effect modifier) for an outcome. Rather it will be or not be a confounder (or effect modifier) for a specific exposure-outcome relationship.

Is gender a confounder or effect modifier?

In this case, the covariable (gender) is neither a confounder nor an effect modifier. We say that it is not a confounder because (1) the crude lies between the 2 stratum-specific estimates, but also (2) the stratum-specific estimates are not more than 10% different than the crude.

Can a confounder variable be also an effect modifier?

Thus while a variable can be a confounder in measure but not an effect modifier in measure, or can be an effect modifier in measure but not a confounder in measure, or an effect modifier in distribution but not a confounder in distribution, a variable that is a confounder in distribution must also be an effect modifier …

Is age a confounder or effect modifier?

Age is a confounding factor because it is associated with the exposure (meaning that older people are more likely to be inactive), and it is also associated with the outcome (because older people are at greater risk of developing heart disease).

Is mediation the same as effect modification?

The notions of effect modification, interaction and mediation represent conceptually different, although potentially interdependent notions. These subtle different notions address different research aims, which are related to different aspects of an exposure–outcome relationship (Box 1).

Is age an effect modifier?

Age: An effect modifier of the association between allergic rhinitis and Otitis media with effusion. Laryngoscope.

How do you address a effect modification?

One common way of dealing with effect modification is examine the association separately for each level of the third variable. For example, suppose a clinical trial is conducted and the drug is shown to result in a statistically significant reduction in total cholesterol.

What is an example of an effect modifier?