Vasunilashorn et al., Quantifying the Severity of a Delirium Episode throughout Hospitalization:

The Combined Importance of Intensity and Duration

Online-Only Supplemental Information

This supplement provides further details on a more comprehensive set of 9 delirium episode severity measures, of which a subset are presented in the text, as well as information on additional analyses.

Table of Contents
Page
eTable 1. Nine Delirium Episode Severity Measures: Mathematical Expressions and Descriptions / 2
eTable 2. Association of Nine Delirium Episode Severity Measures with Three 90-Day Outcomes (Death, Nursing Home Residence, and Readmission) in Project Recovery / 3-4
eTable 3. Spearman Correlation Matrix of the Delirium Episode Severity Measures / 5
eTable 4. C-statistics of Combination Delirium Episode Severity Measures with 30-Day Outcomes in Project Recovery / 6
eFigure 1. Flowchart of the Successful Aging after Elective Surgery Study / 7
eFigure 2. Flowchart of Project Recovery / 8
eFigure 3. Scatterplot of the delirium duration (number of delirium days) by delirium intensity (peak CAM-S) in Project Recovery / 9
eFigure 4. Scatterplot of delirium duration (number of delirium days) by delirium intensity (peak CAM-S) in SAGES / 10
Online-Only Supplemental Text: Additional analyses / 11-13

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eTable 1. Nine Delirium Episode Severity Measures: Mathematical Expressions and Descriptions

Y=Confusion Assessment Method-Severity (CAM-S) score; D=total # days in the hospital; d=# days with delirium; abs=Absolute value; MMSE=Mini Mental State Exam

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eTable 2. Association of Nine Delirium Episode Severity Measures with Three 90-Day Outcomes (Death, Nursing Home Residence, and Readmission) in Project Recovery

eTable 2 (cont.)

*p<.05; RR=Relative Risk; Ref=Referent Group; C-statistic: for continuous measure (for categorical measure) – used as a metric for comparison across measures; high values not expected (see text for details)

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eTable 3. Spearman Correlation Matrix of the Delirium Episode Severity Measures

This table includes a more comprehensive set of measures examined, of which a subset are presented in the text.

CAM-S=Confusion Assessment Method-Severity; Sum CAM-S=Sum of all CAM-S scores; Sum CAM-S, Delirium Days=Sum of all CAM-S Scores, Only on Delirium Days

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eTable 4. C-statistics of Individual and Combination Delirium Episode Severity Measures with 30-Day Outcomes in Project Recovery

C-Statistic*
Combination Delirium Episode Severity Measure / Death / Nursing Home Residence or Death / Readmission or Death
Requires Delirium Intensity:
Full combination measure* / 0.71 / 0.71 / 0.59
Requires Information on Delirium Duration and Delirium at Discharge:
Alternate combination measure** / 0.69 / 0.67 / 0.58

*Includes: Sum of All CAM-S Scores + Delirium at Discharge + Total Number of Delirium Days + Change in Cognition

**Includes: Delirium at Discharge + Total Number of Delirium Days + Change in Cognition

***C-statistic: used as a metric for comparison across measures; high values not expected (see text for details)

eFigure 1. Flow chart of Successful AGing after Elective Surgery Study

*Ineligible if: not residing within 50 miles, evidence of dementia, rescheduled surgery, prior hospitalization, severe blindness or deafness

eFigure 2. Flow chart of Project Recovery


eFigure 3. Scatterplot of the delirium duration (number of delirium days) by delirium intensity (peak CAM-S) in Project Recovery

CAM-S=Confusion Assessment Method-Severity
Note: CAM-S scores can be computed for patients with and without delirium

eFigure 4. Scatterplot of delirium duration (number of delirium days) by delirium intensity (peak CAM-S) in SAGES

CAM-S=Confusion Assessment Method-Severity, SAGES= Successful AGing after Elective Surgery Study

Note: CAM-S scores can be computed for patients with and without delirium

Online-Only Supplemental Text

Additional Analyses

We conducted two sets of additional analyses. The first set aimed to explore the importance of delirium intensity versus duration. We conducted a stratified analysis of the delirium episode severity measure ‘peak CAM-S x delirium days’ to determine whether a severe (intense) delirium over a single day was associated with poorer clinical outcomes compared to a less severe (intense) delirium over ≥2 days. The second set explored the association between combination measures of delirium episode severity and clinical outcomes in Project Recovery. The Methods for both sets of additional analyses are described in greater detail below.

Set One

Methods

To explore the importance of delirium intensity versus duration, we conducted a stratified analysis of the delirium episode severity measure ‘peak CAM-S x delirium days’ to determine whether a severe (intense) delirium over a single day was associated with poorer clinical outcomes compared to a less severe (intense) delirium over ≥2 days. The cutpoint for a ‘severe delirium,’ defined as CAM-S score ≥9, was based on the median CAM-S score separating the upper 50% of the sample-based distribution from the lower half. Using the same analytic models described in the manuscript, we examined the association between this alternate delirium episode severity measure and the 30-day outcomes in Project Recovery.

Results

The number of patients within the two extreme comparison groups of intensity and duration was small. For example, the Ns for the outcome of nursing home placement at 30 days were: 1) peak CAM-S ≥9 with a short number of delirium days (n=2), and 2) peak CAM-S <9 with a long number of delirium days (n=8). Given this, we present a scatterplot of the distribution of delirium days by peak CAM-scores in Project Recovery and SAGES (eFigures 3 and 4). In these samples, the measures were highly correlated, and thus limited our ability to separately evaluate the relative effects of intensity and duration.

Set Two

Methods

Two combination delirium episode severity measures were created based on the requirement that all individual measures not be highly correlated with one another (Spearman correlation <0.55). If two or more measures were highly correlated, the measure with the strongest associations with post-hospital outcomes was selected. The full combination score included four measures, which were individually dichotomized at the median score based on sample distributions (1=above median, 0=below median) and summed (range 0-4). The alternate combination score excluded the delirium intensity measure since this may not be measured daily in all settings (range 0-3).

Results

Based on their c-statistics associated with our clinical outcomes, neither of the two delirium episode severity combination measures was superior to the sum of all CAM-S scores alone. The full delirium episode severity combination score resulted in a higher c-statistic for all outcomes compared to the alternate combination score (that excluded sum of all CAM-S scores); however, this difference was relatively modest (ranging from a 0.1 difference for costs/day and readmission to a 0.4 difference for nursing home residence; eTable 4).

References

1.  Covinsky KE, Palmer M, Fortinsky RH, Counsell SR, Stewart AL, Kresevic D, et al. Loss of independence in activities of daily living in older adults hospitalized with medical illnesses: increased vulnerability with age. J Am Geriatr Soc 2003;51:451-8.

2.  Inouye SK, Boagardus ST Jr, Baker DI, Leo-Summers L, Cooney LM Jr. The Hospital Elder Life Program: A model of care to prevent cognitive and functional decline in older hospitalized patients. Hospital Elder Life Program. J Am Geriatr Soc 2000;48:1697-706.

3.  Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. Studies of illness in the aged. The index of ADL: A standardized measure of biological and psychosocial function. JAMA 1963;185:914-9.

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