Variation in US Hospital Mortality Rates for Patients Admitted With COVID-19 During the First 6 Months of the Pandemic

Abstract

Importance: It is unknown how much the mortality of patients with coronavirus disease 2019 (COVID-19) depends on the hospital that cares for them, and whether COVID-19 hospital mortality rates are improving.

Objective: To identify variation in COVID-19 mortality rates and how those rates have changed over the first months of the pandemic.

Design, setting, and participants: This cohort study assessed 38 517 adults who were admitted with COVID-19 to 955 US hospitals from January 1, 2020, to June 30, 2020, and a subset of 27 801 adults (72.2%) who were admitted to 398 of these hospitals that treated at least 10 patients with COVID-19 during 2 periods (January 1 to April 30, 2020, and May 1 to June 30, 2020).

Exposures: Hospital characteristics, including size, the number of intensive care unit beds, academic and profit status, hospital setting, and regional characteristics, including COVID-19 case burden.

Main outcomes and measures: The primary outcome was the hospital's risk-standardized event rate (RSER) of 30-day in-hospital mortality or referral to hospice adjusted for patient-level characteristics, including demographic data, comorbidities, community or nursing facility admission source, and time since January 1, 2020. We examined whether hospital characteristics were associated with RSERs or their change over time.

Results: The mean (SD) age among participants (18 888 men [49.0%]) was 70.2 (15.5) years. The mean (SD) hospital-level RSER for the 955 hospitals was 11.8% (2.5%). The mean RSER in the worst-performing quintile of hospitals was 15.65% compared with 9.06% in the best-performing quintile (absolute difference, 6.59 percentage points; 95% CI, 6.38%-6.80%; P < .001). Mean RSERs in all but 1 of the 398 hospitals improved; 376 (94%) improved by at least 25%. The overall mean (SD) RSER declined from 16.6% (4.0%) to 9.3% (2.1%). The absolute difference in rates of mortality or referral to hospice between the worst- and best-performing quintiles of hospitals decreased from 10.54 percentage points (95% CI, 10.03%-11.05%; P < .001) to 5.59 percentage points (95% CI, 5.33%-5.86%; P < .001). Higher county-level COVID-19 case rates were associated with worse RSERs, and case rate declines were associated with improvement in RSERs.

Conclusions and relevance: Over the first months of the pandemic, COVID-19 mortality rates in this cohort of US hospitals declined. Hospitals did better when the prevalence of COVID-19 in their surrounding communities was lower.

Figure 1.. Hospital-Specific Risk-Standardized Event Rates for 30-Day Mortality or Referral to Hospice

A, Risk-standardized event rates for all 955 hospitals and 38 517 patients. B, Risk-standardized event rates for 398 of these hospitals with patients admitted during the early period (January 1 to April 30, 2020 [gray dotted line indicates observed event rate during this period]). C, Substantially lower risk-standardized event rates for the same 398 hospitals (not necessarily in the same order) with patients admitted in the late period (May 1 to June 30, 2020 [gray dotted line indicates observed event rate during this period]). The blue dashed line representing the overall 2-period observed risk rate is the same in B and C to facilitate comparison. The dark blue dots represent the hospitals with a risk-standardized event rate below the overall observed rate, and the yellow dots represent those above. The gray shaded area indicates the interquartile range for the risk-standardized event estimate. A numerically higher rank corresponds to worse performance.

Figure 2.. Two-Period Change in Hospital-Level Risk-Standardized Event Rates Between the Early and Late Periods

Of 398 hospitals with at least 10 inpatients admitted with coronavirus disease 2019 (COVID-19) during each period, 397 improved their scores from the early period to the late period, shown by vertical distance below the horizontal dashed line in the Bland-Altman plot. The 95 hospitals in the grey region revealed at least a 50% reduction in event rate. The 281 hospitals in the orange region revealed a 25% to 50% reduction in event rate. The 21 hospitals in the beige region revealed a reduction of less than 25% in event rates. The single hospital in the yellow region revealed only a small increase in score. The general sloping of the scatter downward to the right suggests that hospitals with worse overall scores tended to show the most improvement.

Figure 3.. Hospital Characteristics Associated With Change in Risk-Standardized Event Rates Between the Early and Late Periods in 398 Hospitals

Negative change in risk-standardized event rates from the late period to the early period (shown to the left of the dotted line) reflect characteristics associated with an improvement in hospital risk-standardized event rates. Higher early period community coronavirus disease 2019 (COVID-19) case rates were associated with decreases in late period risk-standardized event rates, and increases in community COVID-19 case rates were associated with increases in late period risk-standardized event rates, adjusting for other factors. ICU indicates intensive care unit.