The prevailing definition of a hospital readmission is a hospital admission that occurs within a specified time frame after discharge from the first or index admission. This definition may be questionable for studies with long or indefinite time frames during which the effect of interventions in the index admission will likely wane, making it less appropriate to classify a later hospitalization as a readmission. The current study proposes an alternative definition of readmission and compares the new definition to the traditional one. The comparison shows that the new method is more conceptually correct because it takes into account the waning effect of the index admission. It can identify readmissions regardless of when they occur. It increases a readmission sample size and thus statistical power.