Confounder analysis for LOGISTIC regression

#1
Hi there,
I have the following situation:
I have a logistic regression analysis, in which I have 3 variables:
The dependent variable- dichotomous- (complication/no complication).
The independent variable- continuous variable- no. of days passed since hospitalization.
The confounding variable- also continuous variable- CCI Index.
How do I perform such an analysis in SPSS? How do I interpret the results? Is there anything to read or a YouTube video explaining that?
Many thanks and best regards!
 

hlsmith

Omega Contributor
#2
What do you think is the confounder?

Is complication post-discharge?

What is your sample size and how many complications?

What is the range for CCI index and what exactly is the instrument use?

CCI and days may be correlate.

-sorry i dont use SPSS.
 
#3
I would also add, there are some general guidelines for confounding, some sources have more extensive definitions but the following two are generally consistent:
1. The confounder should be associated with the exposure (predictor) but not a consequence of the exposure
2. The confounder should be associated with the disease (outcome) but not a consequence of the disease

The two types of conditions stated above can be applied based on the data you have, but can also take into consideration the body of evidence that exists (i.e. the literature on your specific topic). For assessing confounding based on your data, researchers typically calculate how much the adjusted and unadjusted odds ratio differ, usually using some arbitrary value such as 10% or 20% (i.e. the adjusted OR + 10% and - 10%). Sometimes this is frowned upon because this procedure is specific to your dataset, which is why the definition considering the body of evidence is also common (and is probably what informed the decision to collect data on the potential confounder anyway). In many cases both definitions should inform your decision on whether or not to adjust.

In terms of interpreting the effect, compare the adjusted and unadjusted odds ratios, if they are meaningfully different this is generally taken to provide evidence of confounding.