The ratchet effect: dramatic and sustained changes in health care utilization following admission to hospital with chronic disease

Abstract

Objective: To describe the previously unexamined association between admissions to hospital with chronic disease and changes in all-cause health service utilization over time.

Research design: A cohort study examining the population of Western Australia with hospitalizations for chronic disease from 2002 to 2010. A "rolling" clearance period is used to define "cardinal events," that is, a disease-specific diagnosis upon hospital admission, where such an event has not occurred in the previous 2 years. Changes in the rate of cardinal events associated with diagnoses of heart failure, type 2 diabetes, chronic obstructive pulmonary disease, cataract with diabetes, asthma, and dialysis are examined. Health service utilization (defined as inpatient days or emergency department presentations) 6 years preceding and 4 years following such events is presented.

Results: Cardinal events make up 40%-60% of all chronic disease admissions. A previously undescribed ratchet effect following cardinal events specifically associated with type 2 diabetes, heart failure, and chronic obstructive pulmonary disease is observed. This involves a 2- to 3-fold increase in inpatient days and emergency department presentations that are sustained for at least 4 years.

Conclusions: Cardinal events represent an important reference point to understand the impact of chronic disease on health service utilization. Events that herald such a marked transition in health service demand have not been previously described.

FIGURE 1

Cardinal and noncardinal admissions over time. Shown is the number of admissions in each year from 2004 to 2008, for each of the conditions examined. The admissions are separated into those identifiable as cardinal events, and those that are not.

FIGURE 2

A–F, Longitudinal analysis of inpatient days per year around cardinal events. Shown is the mean inpatient days per year (and 95% confidence bands) in the 6 years before and 4 years following a cardinal event for each of the 6 conditions examined. The number of cardinal events at time zero (marked with a dotted line) in each analysis is indicated (n₀).

FIGURE 3

A–F, Longitudinal analysis of emergency department presentations per year around cardinal events. Shown is the mean emergency department presentations per year (and 95% confidence bands) in the 6 years before and 4 years following a cardinal event for each of the 6 conditions examined. The number of cardinal events at time zero (marked with a dotted line) in each analysis is indicated (n₀).

FIGURE 4

Total hospital utilization in the periods before, around, and after cardinal events. A, Shown are the mean (and 95% confidence interval) of total inpatient days associated with a cardinal event, in the 6 years before the event (up to 31 d before the event), in the period around the event (from day −30 to day +30), and in the 4 years after the event (from +31 d onward). Note that dialysis inpatient days are not indicated due to being off scale. B, Shown are the mean (and 95% confidence interval) of total emergency department presentations associated with a cardinal event, in the 6 years before to the event (up to 31 d before the event), in the period around the event (from day −30 to day +30), and in the 4 years after the event (from +31 d onward).