Just something to throw out there - from what I've been told of medical practices in China and possibly some other Asian countries, it wouldn't surprise me if "awareness" played a role in IBD conditions being diagnosed.
It could be a similar situation to reported official economic numbers that few believe.
I had a good friend from China that I worked with. He was trained to be a dentist in his country, but found he preferred to work in sales for the medical industry. His wife was head nurse at a local hospital and member of the party.
As I've seen you mention Kiny about Chinese, my friend was always receiving antibiotic shots. It would surprise me at how frequently he did this. At the slightest sign of a cold he would mention going to the hospital to receive an antibiotic shot. Sometimes his wife would bring home similar medicine.
He also developed a severe stomach problem that was undiagnosed. It was becoming worse over time. Last I heard he mentioned that he was now bed ridden due to stomach pains a good portion of the time. Of course hard to say if his GI problem was caused by the many antibiotic shots or not, or even what disease he has. It made me wonder though.
Something disturbing my friend would mention about medicine in his country is that diagnosis all to often depended upon how much money one had to give as a bribe. For example, if a poor person showed up in the hospital with cancer, the doctor could say no, you do not have cancer, you have muscle pains, take some pain medicine, and go home. On the other hand, if the person was wealthy and willing to give money under the table, whether or not if the cancer could be cured, the doctor would diagnosis the patient with the condition and begin treatment.
Who knows what is going on with the incidence of IBD conditions in Asia, but it wouldn't surprise me if the growing economic wealth seen in Asia is playing a role in IBD diseases being increasingly diagnosed.