We had read a similar line in Revelation 16:9. John repeats that the heart of man is so very hard and desperately corrupt, so as to prepare for the work of the sixth angel. See Leviticus 26:1–46 and Romans 1:18–32 for examples of how hardening leads to further chastisement.
11 and cursed the God of heaven for their pain and sores. They did not repent of their deeds.