Association between ICU admission during off-hours and in-hospital mortality: a multicenter registry in Japan.

Background: The effect of ICU admission time on patient outcomes has been shown to be controversial in several studies from a number of countries. The imbalance between ICU staffing and medical resources during off-hours possibly influences the outcome for critically ill or injured patients. Here, we aimed to evaluate the association between ICU admission during off-hours and in-hospital mortality in Japan.