Those with more severe underlying disease have more frequent exacerbations: in mild disease 1.8 per year, moderate 2 to 3 per year, and severe 3.4 per year.
Tveganje je večje pri revnih ljudeh, čeprav ni jasno, ali je to zaradi revščine same ali zaradi drugih dejavnikov tveganja, ki so z revščino povezani, kot sta na primer onesnaženje zraka in podhranjenost.