BackgroundIn-hospital cardiac arrest (IHCA) is common and often fatal. However, the association between timing of cardiac arrest and likelihood of survival to discharge, neurological status, and subsequent hospital length of stay (LOS) is unknown. MethodsWithin the Get-With-The-Guidelines Resuscitation registry, we identified 175,904 patients between 2000 and 2014 with an IHCA. Time from admission to IHCA was categorized as <3, 3–7, or >7days from admission. Multivariable hierarchical logistic regression models examined the association between timing of IHCA and survival to discharge, and, among survivors, favorable neurological survival (cerebral performance category score of 1) and LOS after IHCA. ResultsOverall, 83,811 (47.6%) of IHCAs occurred <3days from admission, whereas 47,713 (27.1%) and 44,380 (25.5%) occurred between 3 and 7 and >7days from admission, respectively. Cardiac arrests occurring later during the hospitalization were associated with lower survival ([reference: <3days]; for 3-7days: adjusted OR 0.93 [0.90–0.96]; for >7days: adjusted OR 0.89 [0.86-0.92]; P<0.01) and favorable neurological survival ([reference: <3days]; for 3-7days: adjusted OR 0.83 [0.77-0.89], for >7days: adjusted OR 0.55 [0.51-0.59]; P<0.01). Among survivors, later timing of IHCA was associated with longer subsequent LOS ([reference: <3days]; for 3-7days: 2.7 additional days [2.2-3.2]; for >7days: 6.8 additional days [6.3-7.3]; P<0.001). ConclusionMost IHCA occur after 3 hospitalization days. Patients with IHCA after 3 hospital days had lower rates of survival to discharge, and, among survivors, lower rates of favorable neurological survival and longer duration of hospitalization from the time of cardiac arrest.