What about widespread use of painkillers? Aspirin, paracetamol and ibuprofen have become common place over this period. Calming the body's immune response might have a beneficial effect on overall health.
I believe swelling is typically caused by individual cells or tissues (or even pockets in the body) building up fluids of one kind or another. Unfortunately cancer can cause this kind of swelling when your liver and/or kidneys shut down. Source: My mom died of breast cancer, and things were not pleasant near the end.
If OP is talking about systemic inflammation...then there may be a link between the two, but it's certainly not the only cause. [2]