Limitations
We conceived and developed an observational study that is known to increase the risk of selection bias. Additionally, in the eICU-CRD database, data are collected from electronic health records of 208 hospitals across the country; however, each hospital populates the data differently, which results in significant missing data. Our statistical models did not include variables with more than 30% missing data, which was a major limitation. In addition, the predicting models were built with the US elderly population as a reference; therefore, its application to different ethnic groups and non-elderly people requires further investigation and validation.