Adjust or not - unbalanced covariables

[Natalia Gonzalez]

Hi all,

I need some guidance regarding adjusting or not adjusting for certain variables. It is a question about concepts.
I am running mixed effects multilinear regression model and I am planning to adjust for some covariables.

Let's say my independent variable (smokers/no smokers), 0 and 1 are the values of this variable. The variable I want to adjust is spicy (for example), and it is 0 or 1.

My question is, can I add this variable "spicy" to the model (adjusting for it), if in nonsmokers "0", it is always "0" and in smokers "1", sometimes there are "0" and others "1"?
How would this affect the results?


Thank you so much

[Carlo Lazzaro]

Natalia:
you can adjust for spicy.
However, nobody can tell you how this will change your results.

[Natalia Gonzalez]

Thank you so much! I reviewed the p-values and coefficients before and after adjusting, the results didn't change much between both models.
I was wondering if there were any specific rules regarding the variable. If possible to adjust for a variable which is not balanced in both groups (of the independent variable)

Thank you so much!

Best regards,
Natalia

[Carlo Lazzaro]

Natalia:
any regression model should give a fair and true view of the data generating process.
You may want to skim through the literature in your research field and see what Others did in the past when presented with the same (or similar) issue.