The incidence and mortality of AE-IPF varies in different studies. Kubo etc. reported that acute exacerbation occurs within 3 years in around 57% of IPF patients, with the mortality of 53%. Study by Kim etc. show that the mortality of AE-IPF reaches 78%. Study by Song etc.demonstrated that the incidence of acute exacerbation of IPF is 35.4%, with over 50% of in-hospital morality, 56% of 1-year mortality and 18.4% of 3-year mortality. Other studies showed that 1-year post-exacerbation mortality is nearly 100%. Data based on the 178 in-hospital IPF patients in the investigators' department during the latest 4 years showed that 58% (102/178) of those patients experienced acute exacerbation at certain stage of disease, with 70 deaths occurred. Among those deaths, 56 cases (83%) were caused by acute exacerbation. It is clear that the high incidence and mortality of AE-IPF is the most essential factors impacting the survival and quality of life of IPF patients, therefore lead to the poor prognosis of IPF.