Quartz | Level 8

## Longitudinal study - how to plot the outcome with CI against time

Hello, everyone

Today I read this research paper "Plozasiran (ARO-APOC3) for Severe Hypertriglyceridemia
The SHASTA-2 Randomized Clinical Trial" (doi:10.1001/jamacardio.2024.0959).

I am very interested in the line of Figure 2. According to my understanding, the model used in this research probably is a linear mixed model, and follow-up time is an independent factor. What I am not sure is how the author estimated the confidence interval of the outcomes in Figure 2? Using the linear mixed model? Or other methods?

Please let me know your ideas. Thank you.

Figure 2

Figure 2

3 REPLIES 3
Super User

## Re: Longitudinal study - how to plot the outcome with CI against time

Check @Rick_SAS blogs:

https://blogs.sas.com/content/iml/2016/06/22/sas-effectplot-statement.html

``````data have;
call streaminit(123);
do subject=1 to 100;
do time=1 to 10;
sex=ifc(rand('bern',0.4),'F','M');
weight=rand('normal',4,100);
height=rand('normal',0,2);
output;
end;
end;
run;

proc mixed data=have;
class  subject sex time;
model weight=height sex time/s;
random int/subject=subject;
repeated time/subject=subject ;
store out=mixedmodel;
run;
proc plm source=mixedmodel;
effectplot INTERACTION(x=time  sliceby=sex /*plotby=CigsPerDay*/ )/limits connect;
run;``````

Quartz | Level 8

## Re: Longitudinal study - how to plot the outcome with CI against time

@Ksharp Hello, Ksharp. Thank you for your answer. Would you mind if you tell me whether it is appropriate to use only one of the random and repeated statements?

I think either the random or repeated statement can adjust the intra-individual relationship.

Tom

Super User

## Re: Longitudinal study - how to plot the outcome with CI against time

Yes. You can. But you have to have TIME variable in MODEL to plot the interaction graph.
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