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Delirium Among Newly Admitted Postacute Facility Patients: Prevalence, Symptoms, and Severity

Hebrew Rehabilitation Center for Aged, Research and Training Institute, Boston, Massachusetts.

	Abstract

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Background. Delirium may persist for weeks or months, and discharging elderly patients quickly from acute care facilities is not uncommon. Therefore, the adverse impact of delirium on loss of independence may occur in the postacute setting rather than in the hospital. The purpose of this study is to describe the prevalence of delirium, delirium symptoms, and severity assessed at admission to postacute facilities.

Methods. Subjects were recruited from seven Boston-area skilled nursing facilities specializing in postacute care. Assessment instruments included the Mini-Mental Status Exam, Delirium Symptom Interview, Memorial Delirium Assessment Scale, and Confusion Assessment Method (CAM) Diagnostic Algorithm. Delirium status was categorized into four groups: full, two or more symptoms, one symptom, and no delirium. Descriptive statistics were calculated and chi-square analyses and an analysis-of-variance were used to examine delirium characteristics by delirium group.

Results. Among 2158 subjects, approximately 16% had full CAM-defined delirium at admission to the postacute facility. In addition, nearly 13% of the subjects had two or more symptoms of delirium, approximately 40% had one delirium symptom, and 32% had no symptoms of delirium. In a comparison of the group with no symptoms of delirium with that with CAM-defined delirium, there was a significant trend toward (a) older age, (b) lower scores on the Mini-Mental Status Exam, (c) more Delirium Symptom Interview symptoms, and (d) higher Memorial Delirium Assessment Scale Scores.

Conclusions. Results indicate that 16% of admissions to postacute facilities have CAM-defined delirium, and over two thirds had at least one delirium symptom. It is not known whether or not postacute staff have the training necessary to detect or manage delirium. Managing delirium may require different strategies and techniques in a postacute setting, thereby requiring further research.

DELIRIUM is underrecognized, affects more than one third of hospitalized elders, and is associated with adverse events that lead to loss of independence after hospitalization (1–7). Given the accelerating trend to discharge elderly patients quickly from acute care facilities, coupled with mounting evidence that delirium may persist for weeks or months (7–9), it is likely that much of the long-term sequelae of delirium may occur in the postacute setting rather than the hospital. Despite its morbid and costly consequences, very little is known about delirium in a postacute setting. We know of only one published study on the prevalence of specific delirium symptoms in a postacute population. That study used secondary data, and its assessments were performed by facility staff not specifically trained to detect delirium (10).

The purpose of this study is to describe the prevalence of delirium, delirium symptoms, and delirium severity assessed at admission to postacute facilities (based on data derived from trained research personnel following established delirium assessment criteria). Analyses were performed for the whole population and by four mutually exclusive and ordinal delirium groups: (a) full syndromal delirium, (b) subsyndromal delirium (two or more symptoms), (c) subsyndromal delirium (one symptom), and (d) no delirium.

	Methods

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Study Population
Subjects were recruited as part of a randomized trial of a Delirium Abatement Program from seven active Boston-area skilled nursing facilities specializing in postacute care. These facilities varied in size from 81 to 224 beds, with 40 to 82 beds Medicare certified. Eligible subjects in this study were aged 65 or older and admitted directly from an acute care facility. They also spoke English, were not hearing impaired, were communicative prior to acute illness, were not admitted for terminal care (life expectancy <6 months), and lived within a 25-mile radius of our research site. Interviews had to be completed within 5 days of admission, preferably within 72 hours.

Assessments of Delirium
During the past decade, instruments have been developed that allow trained research assistants, rather than clinicians, to detect and diagnose delirium and measure its severity (11,12). Using a protocol approved by our Institutional Review Board, a trained research assistant administered a number of diagnostic instruments (described in the paragraphs that follow) to assess delirium, symptoms, and severity.

The Mini-Mental Status Exam (MMSE) (13) is a valid and reliable (12) neuropsychological test that assesses memory, concentration, attention, and language. It yields a score that is a sum of the items with a maximum (best) score of 30. In our case, the MMSE was not used in the traditional fashion to detect cognitive impairment. Instead, following the lead of Inouye and colleagues (14), we used it as a structured mental status assessment, which in conjunction with the Delirium Symptom Interview (DSI) allowed our assessors to score the required items of the Memorial Delirium Assessment Scale (MDAS) and the Confusion Assessment Method (CAM) (see the paragraphs that follow).

The DSI (15) is a valid and reliable structured interview for diagnosing the presence of specific critical symptoms of delirium in an objective and straightforward manner, and it can be administered by lay interviewers. Consistent with the current definition of delirium, modifications were made in the original DSI instrument to separate the symptom of "disturbance of attention" from that of "disturbance of consciousness." Items addressing informal observations of inattention were redirected as triggers to the presence of inattention, a new eighth symptom. Additionally, an item was added to incorporate and rate performance on formal tasks of attention.

The MDAS (16) allows trained research personnel to quantify the severity of delirium on the basis of 10 features, each scored from 0 to 3 for a maximum score of 30. The 10 MDAS features include reduced level of consciousness, disorientation, short-term memory impairment, impaired digit span, reduced ability to maintain and shift attention, disorganized thinking, perceptual disturbance, delusions, decreased or increased psychomotor activity, and sleep–wake cycle disturbance. The MDAS provides an explicit description of the criteria for scoring, can be completed in 5 minutes, and integrates behavioral observations with objective cognitive testing. A higher score indicates greater delirium severity. A three-category variable was created as follows: (a) MDAS score <10 (mild), (b) MDAS score 10–15 (moderate), and (c) MDAS score >15 (severe). This ordinal variable was used with subjects with full delirium. Psychomotor variants of delirium were also defined by using the MDAS (16). The assessor is asked to rate the patient's activity during the interview by indicating whether the patient (a) is hypoactive, (b) is hyperactive, (c) presents elements of both, or (d) is normal. The MDAS was chosen over the Delirium Rating Scale (DRS) (17) because it has been used specifically to evaluate the effectiveness of clinical interventions, and it does not require the judgment of a clinician as does the DRS (17–19).

CAM is a diagnostic algorithm derived from DSM-III-R (Diagnostic and Statistical Manual of Mental Disorders, III, Revised) criteria for delirium that has been validated against a psychiatrist's diagnosis. The CAM allows trained research assistants to diagnose delirium with greater than 95% sensitivity and specificity, even in populations with a high prevalence of dementia (14). The CAM diagnostic algorithm involves four criteria: first, an acute change in mental status with a fluctuating course; second, inattention; third, disorganized thinking; and fourth, an altered level of consciousness. Inattention was defined as the patient having difficulty focusing attention, such as being distracted easily or having difficulty keeping track of what was being said. Disorganized thinking was defined as the patient's speech being disorganized or incoherent, such as rambling or irrelevant conversation, unclear or illogical flow of ideas, or unpredictable switching from subject to subject. Altered level of consciousness was defined as a level of consciousness other than normal (alert), such as vigilant (hyperalert or overly sensitive to environmental stimuli), lethargic (drowsy but easily aroused), or stupor (difficult to arouse) (14).

Delirium Groups
Using the CAM criteria, we categorized delirium status into four mutually exclusive and ordinal groups: delirium (full), subsyndromal delirium (two or more symptoms), subsyndromal delirium (one symptom), and no delirium. Per the CAM algorithm, "delirium (full)" was coded as present if CAM criteria 1 and 2 were present, and either of criterion 3 or 4 was present. "Subsyndromal (two or more symptoms) delirium" was coded as present if two or three of the four criteria were true but the full delirious qualification just given was not true. "Subsyndromal (one symptom) delirium" was coded as present if only one of the four criteria was true. If none of the four criteria were true then the subject's status was classified as "no delirium."

Because whites accounted for over 90% of the ethnicity–race categories, and the other remaining categories were relatively rare, the other ethnicity–race categories were combined into a nonwhite category, and a white versus nonwhite variable was created and used instead of the original ethnicity–race variable.

Statistical Analyses
Means and standard deviations were calculated for continuous variables and percentages were calculated for categorical variables, both for the overall population and the delirium subcategories. Analysis-of-variance tests were performed on continuous variables to determine if their mean values differed by delirium group status. If they differ, post hoc tests (Tukey) were performed to determine which groups differed. Chi-square analyses were performed to determine if the proportions of categorical variables differed by delirium group status. An alpha level of 0.05 was used to determine statistical significance, and all analyses were performed with SAS software (20,21)

	Results

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Entire Population
Of the 2158 subjects, 70% (n = 1510) were women, and 93% (n = 1658) were white; their mean age was 81 years, and their mean time from admission to the completion of assessments was 2.5 days. The average scores for the MMSE and MDAS were 20.9 and 5.9, respectively, and the average number of symptoms (DSI) was 2.4 (Table 1). Of the eight DSI symptoms, disturbance of attention (59%), sleep disturbance (47%), and disorientation (44%) were among the most common. Incoherent speech (30%) and abnormal psychomotor activity (26%) were relatively less common, and fluctuating behavior (16%), perceptual disturbance (13%), and disturbance of consciousness (7%) were among the least common delirium symptoms (Table 2).

Table 5 shows the percent of specific delirium symptoms (derived from the DSI) by delirium group (p <.0001). As expected, there was an ordinal trend, with the percent of delirium symptoms highest in the delirium group, next highest in the subsyndromal (two or more symptoms) group, next highest in the subsyndromal (one symptom) group, and lowest in the no delirium group. There was one minor and subtle exception with sleep disturbance, where the subsyndromal (one symptom) group was slightly higher than the subsyndromal (two or more symptoms) group. Note that sleep disturbances were relatively common in all groups, including the no delirium group.

	Discussion

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Comparing the findings of this study with other similar studies is limited by the scarcity of research on delirium in a postacute population. We recently published a study (10) reporting the prevalence of delirium symptoms at the time of admission to postacute facilities. Of 551 subjects, 23% (n = 126) had delirium symptoms at admission. This prevalence of symptoms was higher than the prevalence of CAM-defined delirium (16%) reported in the current study, but lower than the overall 68% prevalence of any delirium symptoms. However, it is difficult to compare these prevalences because each study used different diagnostic criteria for delirium. Unlike the current study that used the CAM criteria, our previous study designated subjects as having symptoms of delirium if they had any of the following six Minimum Data Set symptoms: easily distracted, periods of altered perception, disorganized speech, periods of restlessness, periods of lethargy, or their mental function varied over the course of the day. Our previous study used secondary data and was also limited by its reliance on delirium assessment performed by facility staff not specifically trained to detect delirium. Previous research has shown that delirium assessments performed by clinical staff are less accurate than those performed by trained research personnel (1,22). Accordingly, the results of our current study may be more representative of the true percentage of delirium symptoms among newly admitted postacute facility patients.

Results of this study emphasize the importance of education and training concerning the detection of delirium symptoms and characteristics. Delirium recognition is often difficult in a postacute facility setting, because staff members responsible for assessing delirium generally have little if any knowledge of the patient's baseline cognitive status. It is essential to have knowledge of a patient's prior cognitive status to prevent delirium from being misclassified as dementia and consequently resulting in inappropriate care. Education and training may be needed to inform staff members how to use other sources of information to determine the baseline cognitive ability of patients, such as medical records and reports from family members. Compounding the challenges of recognition in the postacute setting is our finding that nearly 75% of delirious patients had hypoactive or normal psychomotor features. Inouye has shown that the absence of hyperactivity is a major risk factor for failure of recognition by clinical staff (1). Additional education and training on the management of delirium may also be appropriate, as the management of delirium in a hospital may differ from management in a postacute setting. Finally, sleep disturbances were relatively common in all groups, including the no delirium group (47%). Consequently, these individuals may be administered sleeping medications that in turn may contribute to delirium persistence. Education on delirium prevention, such as the sleep hygiene protocol described by Inouye (23,24), would be useful in this setting.

This study has advantages and limitations worthy of discussion. Unlike our previous study of delirium in a postacute setting (10), this study used a well-established and validated diagnostic algorithm derived from DSM-III-R criteria for delirium, and trained research personnel assessed delirium. The gradient of scores seen in the MMSE, DSI, and MDAS lend additional validity to our CAM-based categorization of delirium. Additionally, this study was able to assess severity of delirium in the postacute setting. Finally, the relatively large sample size of postacute subjects provides the power to detect differences in various measures of delirium across delirium groups.

A limitation of this study is that we do not have outcome data for all these patients because these data were derived from a randomized clinical trial that only enrolled full CAM delirious patients, and we do not have comparable outcome data for the other two subsyndromal and the no delirium groups. The data were obtained from multiple assessors, but they had excellent interrater reliability (kappa = 0.90) (25). Our data were collected from a single metropolitan region but included information from seven facilities. The prevalence of delirium may vary in cities with less pressure to discharge patients from hospitals, or at skilled nursing facilities that admit fewer acute patients. Finally, although our assessments were performed within 2.5 days of admission, we cannot be sure if some of the patients developed delirium after they were admitted to the skilled nursing facility.

Conclusions
To our knowledge, the results of our study offer the only source of information on delirium symptoms and severity, and a CAM-based delirium prevalence in a postacute facility setting. The similarity of delirium prevalence from this study compared with reports of hospital-based prevalence suggests that delirium persists after hospital discharge. It is not known whether or not postacute staff have the training necessary to detect or manage delirium. Furthermore, managing delirium may require different strategies and techniques in a postacute setting. The development and testing of strategies for the detection and management of delirium in a postacute setting is warranted.

	Acknowledgments

 
This research was supported in part by Grant AG 17649 from the National Institute on Aging. Dr. Marcantonio is a recipient of a Paul Beeson Physician Faculty Scholarship in Aging Research.

The authors thank Kerry Clark, Kathryn Johnson, Mary Michaels, Sara VanValkenburg, Melissa McKenna, Jennifer Kettell, Monique Bussell, and Maria Kereshi for their efforts to screen and interview over 2000 patients for this study. The authors also thank Ellen Gornstein, BA, and Pamela A. Heidell, MS, for reviewing this manuscript, and Aleksandra Brenckle, BS, for assistance preparing this manuscript for submission.

Address correspondence to Dan K. Kiely, Hebrew Rehabilitation Center for Aged, Research and Training Institute, 1200 Centre Street, Boston, MA 02131. E-mail: kiely{at}mail.hrca.harvard.edu

	Footnotes

 
Joseph H. Flaherty,, MD

Received August 20, 2002

Accepted September 26, 2002

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