Hello, I have a doubt about the ways of comparing categories in logistic regression. I have 200 subjects with a dependant variable (positive/negative) and I want to test them with an independent variable (IV) of 4 categories (age). I am going to use a logistic regression, but when I do that, I typically use a category of reference in the IV and the rest of categories are contrasted to this category of reference, but since the age is a progressive variable, I would like to compare adjacent categories i.e. comparing each category of the IV to the next category. Is this valid?