Interpreting proc genmod output

I have hospitalization data (nsum) over a 17 year period for 3 different study areas (variables period and area). I have the log of the population as the offset. So, I think I need to be going with negative binomial and for my code I have entered:

proc genmod data=want;
class period area;
model nsum=area period area*period / dist=NB link=log offset=log pop type1;

I am not really interested in estimates just for area or just for period, rather, I am interested in the difference between the areas over the time period. In the output for the interaction of area*period, there are 3 rows for each year in the 17 year period so I have area 1, area 2, and area 3 (reference group). My question is - how do I interpret this output? Is there a way to broadly look at if the 3 areas differ significantly over this time period or do I have to look at the p-values for each year for areas 1 and 2 compared to the reference group?

I also have the LR statistics for type 1 analysis, but I'm not really sure what this is telling me when I look at the p-value for the area*period term. Thanks :)