Length of stay (LOS) is the duration of a single episode of hospitalization. Inpatient days are calculated by subtracting day of admission from day of discharge.
Analysis
A common statistic associated with length of stay is the average length of stay (ALOS), a mean calculated by dividing the sum of inpatient days by the number of patients admissions with the same diagnosis-related group classification. A variation in the calculation of ALOS can be to consider only length of stay during the period under analysis.
Length of stay is typically highly skewed and so statistical approaches taking that into account are recommended. Within regression approaches, linear, log-normal and logistic regression approaches have been applied, but have been criticised by other researchers. This phenomenon reflects the principles of Goodhart's Law, which states that "when a measure becomes a target, it ceases to be a good measure." In the context of healthcare, overemphasis on LOS as a target metric can compromise the quality of patient care.
Non-health usages
The term "average length of stay" (ALOS) is also applicable to other industries, e.g. entertainment, event marketing, trade show and leisure. ALOS is used to determine the length of time an attendee is expected to spend on a site or in a venue and is part of the calculation used to determine the gross sales potential for selling space to vendors etc. and affects everything from parking to sanitation, staffing and food and beverage. Almost all operational aspects can be altered by an attendee's ALOS.