How to test the interaction between strata and treatment groups in a mmrm model?

[Robin_moon]

I constructed a mmrm model as below:

 proc mixed data = have;
 class id treatment week strata;
 model chg = base treatment week treatment*week treatment*strata/ ddfm = KR;
 repeated week/ subject = id type = UN;
 lsmeans treatment*week/ cl alpha = 0.05 diff
 ods output Tests3=tests3 lsmeans=lsmeans diffs=diffs;
 run;

(1) id: represents the patient id;

(2) treatment: contains 2 group, "drug" and "placebo";

(3) chg: change from baseline of hba1c;

(4) base: the value of hba1c at baseline;

(5) week: contains 3 levels: "week8", "week16" and "week24"

(6 )strata: stratification based on the median of baseline hba1c, ie

      group1=patients of those who have baseline hba1c <= median of baseline hba1c;

      group2=patients of those who have baseline hba1c > median of baseline hba1c.

In general, I'd like to know how to the test the interaction between strata and treatment groups. I am not sure if I constructed the model in a right way because I looked at the results (as below), the values of Diffs in LS means were pretty close between strata, but p for interaction was significant. (The Diffs in LS means were got from the output file diffs, and the p for interaction were got from the output file test3.)

I also checked the Diffs in LS means of week8 and week16, the diffs in LS means were all pretty close between 2 strata, but the p for interaction were all significant (p-value < 0.0001). So I am not sure if I interpret the result in the right way. What data should look quite different if the p for interaction is statistically significant? Thanks.