Population-Based Trends in Complexity of Hospital Inpatients

Abstract

Importance: Clinical experience suggests that hospital inpatients have become more complex over time, but few studies have evaluated this impression.

Objective: To assess whether there has been an increase in measures of hospital inpatient complexity over a 15-year period.

Design, setting and participants: This cohort study used population-based administrative health data from nonelective hospitalizations from April 1, 2002, to January 31, 2017, to describe trends in the complexity of inpatients in British Columbia, Canada. Hospitalizations were included for individuals 18 years and older and for which the most responsible diagnosis did not correspond to pregnancy, childbirth, the puerperal period, or the perinatal period. Data analysis was performed from July to November 2023.

Exposure: The passage of time (15-year study interval).

Main outcomes and measures: Measures of complexity included patient characteristics at the time of admission (eg, advanced age, multimorbidity, polypharmacy, recent hospitalization), features of the index hospitalization (eg, admission via the emergency department, multiple acute medical problems, use of intensive care, prolonged length of stay, in-hospital adverse events, in-hospital death), and 30-day outcomes after hospital discharge (eg, unplanned readmission, all-cause mortality). Logistic regression was used to estimate the relative change in each measure of complexity over the entire 15-year study interval.

Results: The final study cohort included 3 367 463 nonelective acute care hospital admissions occurring among 1 272 444 unique individuals (median [IQR] age, 66 [48-79] years; 49.1% female and 50.8% male individuals). Relative to the beginning of the study interval, inpatients at the end of the study interval were more likely to have been admitted via the emergency department (odds ratio [OR], 2.74; 95% CI, 2.71-2.77), to have multimorbidity (OR, 1.50; 95% CI, 1.47-1.53) and polypharmacy (OR, 1.82; 95% CI, 1.78-1.85) at presentation, to receive treatment for 5 or more acute medical issues (OR, 2.06; 95% CI, 2.02-2.09), and to experience an in-hospital adverse event (OR, 1.20; 95% CI, 1.19-1.22). The likelihood of an intensive care unit stay and of in-hospital death declined over the study interval (OR, 0.96; 95% CI, 0.95-0.97, and OR, 0.81; 95% CI, 0.80-0.83, respectively), but the risks of unplanned readmission and death in the 30 days after discharge increased (OR, 1.14; 95% CI, 1.12-1.16, and OR, 1.28; 95% CI, 1.25-1.31, respectively).

Conclusions and relevance: By most measures, hospital inpatients have become more complex over time. Health system planning should account for these trends.

Figure 1.. Patient Flow Diagram

This flow diagram shows how the study cohort was defined. We included all adult hospitalizations in British Columbia unrelated to pregnancy and childbirth. We excluded elective admissions, those with length of stay of zero days, and those involving patients younger than 18 years. ^aSpecific exclusions do not sum to the total number because patients could have more than 1 reason for exclusion.

Figure 2.. Changes in Dichotomized Measures of Complexity, 2002-2017

The forest plot illustrates the relative change in measures of complexity over the 15-year study interval. The y-axis indicates each measure of complexity; x-axis, the ratio comparing the odds that the measure was present at the end of the study interval to the odds of its presence at the beginning. Solid squares represent the point estimates. The 95% CIs (calculated using cluster robust standard errors) are narrow and entirely obscured by the point estimate; they are depicted in the data table. Odds ratios (ORs) greater than 1 indicate that complexity increased over the study interval. Multimorbidity was defined as Charlson Comorbidity Index of 5 or greater; polypharmacy, 10 or more active medications; multiple acute medical problems, 5 or more diagnoses that contributed to the index hospital length of stay; and prolonged length of stay, 10 or more days. Alternate cutoffs were evaluated in sensitivity analyses (eTable 1 in Supplement 1). ED indicates emergency department; ICU, intensive care unit.

Figure 3.. Trends in Continuous Measures of Complexity, 2002-2017

Graphs illustrate the trend in the mean of continuous measures of complexity over the 15-year study interval. Dark blue points correspond to patient factors at admission, and light blue points correspond to features of the hospitalization. Trend lines were generated using locally estimated scatterplot smoothing. While the absolute changes for any given measure were modest, the overall trend suggests increased complexity over time for all measures of complexity. CCI indicates Charlson Comorbidity Index; ICU, intensive care unit; LOS, length of stay.