Original Research Article Measuring the distribution of the length of stay in acute psychiatric units Matthew M. Large 1 , Michael B. Paton 2 , Grant Sara 3,4,5 , Murray Wright 6 , Olav B. Nielssen 7 1 Psychiatrist and Conjoint Senior Lecturer, School of Psychiatry, University of New South Wales, Sydney, Australia; 2 Clinical Director, Mental Health Drug and Alcohol, Northern Sydney Local Hospital Network & Central Coast Local Hospital Network, Macquarie Hospital, Sydney, Australia; 3 Director, InforMH, Mental Health and Drug and Alcohol Office, NSW Health, North Ryde, Australia; 4 Clinical Senior Lecturer, Northern Clinical School, Sydney University, Australia; 5 School of Population Health, University of Queensland, Australia; 6 Formerly Director, Clinical Operations, Mental Health Drug and Alcohol, Greater Southern Area Health Service, NSW, Australia; 7 Psychiatrist and Conjoint Senior Lecturer, Clinical Research Unit for Anxiety and Depression, School of Psychiatry, University of New South Wales at St Vincent’s Hospital, Sydney, Australia Abstract Objective: To examine the distribution of length of stay (LOS) in acute psychiatric units. Method: Analysis of one year of LOS data from twelve acute psychiatric units in New South Wales, Australia. Main findings: LOS had a complex distribution, with a ‘head’ of discharges within a day, a ‘body’ of discharges that approximated an exponential distribution and a ‘tail’ made up of a small group of patients discharged after very long admissions. There were substantial differences between units in the proportions of discharges classified as being in the head and the tail of the LOS distribution. With regards to the traditional measures of central tendency, the median LOS was affected by the proportion of patients discharged within a day, and the mean LOS was strongly influenced by small numbers of very long stay patients. Conclusions: A graphic representation of logarithmically transformed LOS values might assist in under- standing the LOS of individual acute psychiatric units. A modified median LOS, calculated after the removal of patients staying less than a day, was found to be a simple and reliable measure that can potentially provide a more meaningful measure of LOS than the mean or the median LOS. Keywords Length of stay; psychiatric hospital INTRODUCTION Length of stay (LOS) in psychiatric hospitals is of interest to patients, their families, clinicians, service administrators and funding bodies. The Correspondence to: Matthew Large, The Euroa Building, Prince of Wales Hospital, Barker St, Randwick, New South Wales, Australia, 2031. E-mail: mmbl@bigpond.com First published online date: 05/08/2011 78 Ó NAPICU 2012:8:7887 Journal of Psychiatric Intensive Care Journal of Psychiatric Intensive Care Vol.8 No.2:7887 doi:10.1017/S1742646411000227 Ó NAPICU 2012