 geographical region, the total number of discharges, or study design (Additional file [0](#MOESM0){ref-type="media"}: Figures S0--S0).Fig. 0Forest plots of the association between nighttime discharge from the ICU and hospital mortality. The size of each *square* is proportional to the study weight. *Open diamond* represents the overall pooled OR. *D + L* random effects, *I-V* fixed effects 