Psychosomatics 47:414-420, October 2006
doi: 10.1176/appi.psy.47.5.414
© 2006 Academy of Psychosomatic Medicine
Cognitive-Disorder Diagnoses in Inpatient Psychosomatic-Medicine Consultations: Associations With Age and Length of Stay
James A. Bourgeois, O.D., M.D.,
Donald M. Hilty, M.D.,
Jacob A. Wegelin, Ph.D., and
Robert E. Hales, M.D., M.B.A.
Received November 15, 2004; revised August 29, 2005; accepted October 4, 2005. From the Dept. of Psychiatry and Behavioral Sciences and the Division of Biostatistics, UC Davis Medical Center. Address correspondence and reprint requests to Dr. Bourgeois, Dept. of Psychiatry and Behavioral Sciences, Univ. of California, Davis Medical Center, 2230 Stockton Blvd., Sacramento, CA 95817.
e-mail: james.bourgeois{at}ucdmc.ucdavis.edu
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ABSTRACT
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Authors reviewed consecutive charts of 155 cognitive-disorder patients from a psychosomatic medicine service in 2001, analyzing factors of age, cognitive-disorder diagnosis, and length of stay. Mean length of stay for this cohort exceeded the typical hospital length of stay, and decreased with age. Increased age was associated with a decreased probability of a delirium-only diagnosis, and was strongly associated with an increased probability of a dementia diagnosis. Among those with dementia, the probability of having an additional diagnosis of delirium was unrelated to age. The case-mix of cognitive disorders differs with age, whereas cognitive disorders are associated with increased length of stay for adult patients of all ages.
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INTRODUCTION
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Cognitive disorders, primarily dementia and delirium, are common in psychosomatic-medicine practice. As patients age and are at higher risk for dementia, the risk of delirium increases. Diagnosis and management of cognitive disorders is crucial in the practice of psychosomatic medicine because such patients have a greater length of hospital stay and poorer functional and survival outcomes. The fact that age increases the rate of diagnosis of cognitive disorders is not surprising; yet the relative risk of dementia and delirium as separate or concurrent illnesses has been incompletely addressed in the literature.
The literature reports both the rates of diagnosis of the cognitive disorders in psychosomatic-medicine practice and the effects of cognitive disorders (included under the rubric "organic mental disorders" in the older literature) on hospital length of stay and other functional outcomes.1–19 Previous studies of "organic mental disorders" include psychotic, mood, anxiety, and personality disorders from "organic" etiologies, but these illnesses are not listed as "cognitive" disorders in DSM-IV and DSM-IV-TR. A variety of hospital populations have been studied regarding organic mental disorders or cognitive-disorder diagnosis patterns. The methodological approaches of these studies vary widely, and the results are summarized in Table 1 [A] and [B]).
Differential Rates of Cognitive-Disorder Diagnosis
Two previous studies of cognitive-disorder diagnosis in psychosomatic-medicine populations addressed the conditions of dementia, delirium, and dementia with comorbid delirium. Trzepacz et al.1 reviewed 133 cases. Forty-nine-percent of patients were over age 65. Dementia was diagnosed in 45 (34%), delirium in 77 (58%), and 11 (8%) were diagnosed as dementia with delirium. Among patients under age 65, 40 (62%) were diagnosed with delirium and 15 (23%) with dementia, whereas among patients over age 65; delirium was diagnosed in 37 (54%) and dementia in 30 (44%). Jitapunkul et al.2 studied 184 patients over age 60 and found 61 to have delirium and/or dementia. Dementia was the diagnosis in 21 (34%) of the cognitively impaired patients, delirium in 28 (46%), and delirium plus dementia in 12 (20%). Illustrating the covariance of dementia and delirium, 30% of their delirium patients had underlying dementia, whereas 34% of their dementia patients also had delirium. Other similar studies of cognitive-disorder diagnoses in psychosomatic-medicine populations with cognitive impairment addressed the diagnosis of delirium or dementia, but not both comorbidly3–7 (see Table 1 [A]). Among these studies summarized in Table 1 [A], the rate of dementia diagnosis among cognitive-disorder patients ranged from 34% to 73%, whereas the rate of delirium diagnosis ranged from 27% to 58%. In a different approach, other previous studies examined cohorts of primarily identified delirium or dementia patients and studied cognitive-disorder comorbidity by use of various methods8–14 (Table 1 [B]). All the studies using this type of research method showed substantial rates of comorbid dementia and delirium in older patients.
Cognitive-Disorder Diagnosis, Hospital Length of Stay, and Functional Outcomes
The other approach of studies has been to focus on the effects of organic or cognitive disorders on patients’ length of stay and other indices of clinical outcomes. Consistently, cognitive impairment has been associated with longer length of stay and poorer functional status. In the Hales et al. study,4 length of stay for cases with an organic mental disorder was six times the typical hospital length of stay (60.1 days for affected patients versus 10.5 days for a typical length of stay). Holmes and House7 found that both cognitive-disorder illnesses correlated with increased length of stay. In Manos and Wu’s study,8 dementia-plus-delirium patients had a longer length of stay than non-dementia delirium cases (20.4 days versus 10.9 days). In the Francis et al. study,13 patients with delirium had a mean length of stay of 12.1 days versus 7.2 for cases without delirium.13 In the Erkinjuntti et al. study,9 length of stay for dementia was 45 days, versus 14 days for non-dementia patients. Fulop et al.15 studied 467 geriatric medical/surgical admissions and found 126 cases (27%) with cognitive impairment, which was associated with an increase in hospital length of stay from 10.6 to 14.6 days.
Rockwood16 noted that patients over age 65 with "delayed discharge" were at significantly higher risk for delirium or dementia. In a meta-analysis of the prognosis of delirium in older patients, Cole and Primeau reviewed eight reports, totaling 573 cases of delirium, in patients over age 65.17 At 1-month follow-up after identification of delirium, 46% of delirium patients were institutionalized, and only 55% had experienced improved mental functioning. Delirium was associated with longer length of stay (20.7 days versus 8.9 days), higher mortality rate, and higher rate of institutionalization than non-delirium patients.
Kato et al.18 assessed patients’ cognition at psychiatric admission and demonstrated that decreased cognitive status correlated with increased length of stay. Litaker et al.19 studied 500 elective surgery patients. Postoperative delirium was diagnosed in 57 (11%). Age over 70, preexisting cognitive impairment (23% of cases), preoperative functional limitations, and previous episodes of delirium all increased the risk of postoperative delirium.
In light of the above-cited literature, we sought to analyze our data along three dimensions: 1) Rates of diagnosis of cognitive-disorder cases with dementia, delirium, or dementia-plus-delirium; 2) The relationship of these rates of diagnosis to patient age; and 3) The relationship of length of stay to cognitive-disorder diagnosis and age.
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METHOD
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The University of California, Davis Medical Center (UC-DMC) is a 528-bed, tertiary-care academic medical center. In addition to a full range of medical and surgical services, the medical center maintains an active psychosomatic-medicine service staffed by faculty and resident psychiatrists and a clinical nurse-specialist. The psychosomatic-medicine service does 1,300 new consultations annually, and consultation–liaison service billing data identify cognitive-disorder diagnoses status after psychosomatic-medicine consultation for 30% of cases seen by the psychosomatic medicine service.
A search was done of calendar year 2001 records to identify patients with such a diagnosis, and full information was gathered on the basis of a thorough psychiatric history and examination for a work-up of cognitive disorders. Cognitive-disorder diagnoses were verified by chart review of records (JAB). Presence or absence of delirium and presence or absence of dementia were noted for each chart, length of stay for the admission generating the consultation, and subject’s gender and age, all obtained during the same chart review. Cases with incomplete data were excluded, but the excluded charts did not differ significantly from the included charts in terms of age or cognitive-disorder diagnoses. The review generated instances of 155 consecutive patients with cognitive disorders.
To test for relationships between age, gender, and diagnostic category, multiple-regression models were fit, with age as the outcome and diagnosis and gender as predictors, and gender and diagnosis were cross-tabulated. To quantify the probability of having a particular diagnosis as a function of age, logistic-regression models were fit and chi-square deviance tests performed to compare models with and without age as a predictor. To test for relationships between length of stay and age, length of stay and gender, and length of stay and diagnostic category, regression models were fit, with length of stay as the outcome and with age, diagnosis, and gender as predictors. Length of stay is positive and skewed toward high values. Accordingly, the natural logarithm (log) of length of stay was used in all analyses to reduce the effect of outliers, and the geometric mean of length of stay was computed, rather than the usual (arithmetic) mean. The distribution of residuals from the multivariate-regression model was examined by means of a normal quantile plot in order to validate the choice of log-transformation. Results are reported on the original scale. Two different models for the relationship between age and length of stay were considered: one in which age was treated continuously, and one in which age was dichotomized between age 18–64 and 65-or-older.
This project was approved by the Institutional Research Board at UC Davis Medical Center.
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RESULTS
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No relationship was found between gender and diagnosis, but the mean age for women was greater than for men. The numbers of men and women in each diagnostic category, and their mean ages are shown in Table 2.
Mean age differed between patients with delirium-only and those with dementia or delirium-and-dementia, but there was no evidence of a difference in age between patients with dementia-only and those with both dementia and delirium. Mean age by diagnosis is shown in Table 3.
In accordance with the age differences between the diagnostic groups, increased age was associated with a decreased probability of having a delirium-only diagnosis in those with a cognitive-disorder diagnosis and strongly associated with an increased probability of having a dementia diagnosis. In patients with a dementia diagnosis, there was no evidence that the probability of also having a delirium diagnosis changed with age. The number and percentage of patients in each diagnostic category are broken down by age category in Table 4.
Length of stay is shown by diagnosis and age in Table 5. Differences in length of stay were associated with age but not with diagnostic group. When age was dichotomized between 18–64 and over-65, on the other hand, the difference did not attain statistical significance, although geometric mean length of stay was less in the geriatric group (11.0 days) than in the younger group (14.4 days). Thus, the current data support a continuous relationship between age and length of stay, rather than an abrupt change at age 65. The geometric means for the first two age categories (covering ages 18–39) are identical up to rounding, whereas, for greater ages, length of stay decreases with age. This suggests a quadratic or curved relationship, in which differences in average length of stay associated with age are greater for older people. The evidence for such a relationship did not attain statistical significance, however.
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DISCUSSION
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We addressed the relative diagnostic rates of dementia, delirium, and dementia-plus-delirium among 155 patients with cognitive disorders on psychosomatic-medicine consultation. The profile of diagnosis rates of cognitive disorders changed with age. Younger patients were more likely to be diagnosed with delirium as the sole cognitive disorder, whereas older patients were more likely to be diagnosed with dementia or dementia-plus-delirium and less likely to be diagnosed with delirium as the sole cognitive-disorder diagnosis.
Mean length of stay was high in the cognitive-disorder patients. These findings support those of some other studies that have found a substantial risk of comorbid cognitive disorders and/or increased length of stay in cognitively impaired psychosomatic-medicine patients.1–4,8–13,15,17,18 Comparison of our studies must take into account methodological differences. Previous studies have often combined disorders of cognitive impairment into a single category of "organic mental disorders," in the older literature, or "cognitive disorders," in the more recent literature.
Several previous studies examined the frequency of a delirium diagnosis in various study cohorts, and thus did not examine the frequency of a dementia diagnosis in the absence of delirium.8,10–14 However, several such studies did address the presence of dementia in identified delirium patients, corresponding to cases in the present study where both diagnoses were rendered. The studies examining length of stay for organic mental disorders or cognitive disorders were completed over a wide range of study years, used different diagnostic systems, examined different clinical cohorts, and included international populations. Therefore, it is more reasonable to look at a general trend toward increased length of stay in patients with cognitive impairment versus those without.
The overall mean length of stay was 13 days, versus the medical center’s typical length of stay of only 3 days for the year 2001. This suggests either a greater degree of medical complexity in cognitively-disordered patients, profound systems challenges in arranging for appropriate discharge placement for these patients, or, more likely, a combination of both factors. This mirrors previous studies that have shown excess length of stay associated with cognitive impairment. Given that our study was accomplished during the managed-care era, it appears that this effect of excess length of stay associated with cognitive impairment has persisted in the modern era, despite a shortening of length of stay in medical centers for non-cognitively impaired patients. Further detailed study of the individual cases could elucidate the relative effects of concurrent medical/surgical illness and social/logistical challenges on the increased length of stay in this group.
Increased age among cognitive-disorder patients was associated with shorter mean length of stay among these patients, a somewhat counterintuitive finding. The relationship between age and length of stay was continuous, and, in fact, a model with age dichotomized into an 18–64 age-group and an over-65 age-group did not yield a statistically significant relationship with length of stay. The fact that patients in the United States over 65 are typically covered by Medicare insurance (whereas younger patients are typically not) could affect discharge placement if the availability of Medicare resources facilitates discharge of the older patients. However, the continuous nature of this relationship suggests that it may not be wholly due to an abrupt change in type of insurance status at age 65. One likely factor is that the UC-Davis Medical Center has a Level I Trauma Center and is the regional leader in trauma surgical care. It is therefore conceivable that many of the cognitively-impaired patients, especially the younger patients, had an excess length of stay because of major trauma (including head trauma) and its attendant surgical interventions and complications.
Strengths of our study include the fact that all records were from a single institution with a robust academic psychosomatic-medicine service. The cognitive-disorder diagnoses were all made by a small group of psychosomatic-medicine psychiatrists, suggesting reasonable interrater diagnostic reliability. Length-of-stay data were derived directly from discharge documents and thus are likely to be accurate. The relatively robust size of the delirium group in patients under 65 (79 cases) and the associated length of stay of 14.8 days is indicative of the medical complexity and ultimate functional compromise seen in this population of nongeriatric cognitively-disordered patients. This excess length of stay leads to increased medical resource consumption, even without comorbid dementia, in a nongeriatric group.
Limitations of the study include reliance on a retrospective approach and the need to accept the validity of clinically-derived diagnoses, rather than diagnoses made from structured interviews such as the Structured Clinical Interview for DSM-IV. Also, the overall group size of 155, although a reasonable size when taken as a whole, results in some relatively small subgroups when broken down according to the chosen parameters. This may limit any conclusions drawn. This could be addressed in future studies by use of a larger data source and/or a multicenter study.
Clinical Implications of Dementia-and-Delirium Comorbidity
In previous studies where it was addressed, and consistent with our findings, there has been an increased frequency of comorbid dementia and delirium reported in patients over age 65. Given this risk, plus the fact that our study and several others indicated substantial risk of dementia in patients under age 65 who present with delirium, it makes clinical sense to complete a standard dementia evaluation (e.g., neuroimaging, full cognitive examination, assessment of dementia risk factors, full laboratory studies) with a low clinical threshold, in delirium cases, especially in the geriatric population. This imperative can be framed as understanding the premorbid cognitive state of the patient so as to examine the crucial issue of vulnerability for delirium. Although difficult to validate prospectively, close vigilance for occult dementia in all patients who present with delirium is recommended. Conversely, it may be reasonable to have a higher index of suspicion for cognitive impairment in hospital patients with a long length of stay, because subtle cognitive impairment may be implicated in patients failing to progress with their functional recovery. Because of the long length of stay associated with cognitive disorders, physicians encountering these patients in the general hospital should be alert to the possibility that these patients may require significant help and/or may experience significant challenges in safe discharge planning.
The majority of patients over the age of 65 are covered by Medicare. Medicare uses a diagnosis-related group reimbursement system based upon the primary diagnosis and the severity of illness. Medicare then pays the medical center a fixed amount of money for each episode of care for treatment for a specified condition. With longer length of stay in cognitively-impaired patients, the medical center is then receiving much less money, on a daily basis, than it does for non–cognitively-impaired patients. Medical centers would be well-served to provide increased financial support to psychosomatic-medicine consultant clinical services, with the goals of identifying cognitively-impaired patients early in their stay, treating them with appropriate medications and psychosocial interventions, and aggressively arranging discharge and follow-up.
Recommendations for Further Research
Further research to refine the paradigms described in the present study might include stratification by case-mix, detailed consideration of other psychiatric illness affecting length of stay and/or complicating clinical management, and a larger, perhaps multicenter, database. Also, studies such as ours could be replicated periodically to see whether systems factors in healthcare delivery, such as the availability of geropsychiatry units and hospice care models for dementia, might affect the need for excess length of stay in the medical center for cognitively-impaired patients. Finally, studies need to determine whether, when cognitively-impaired patients are seen by a psychosomatic-medicine service early in their stay, the length of stay for these patients is reduced, resulting in increased net revenue for the medical center.
In conclusion, the cognitive disorders of dementia and delirium were both associated with a significantly prolonged length of stay in a major academic medical center. This effect was present for both geriatric and nongeriatric patients. Physicians assessing patients for cognitive impairment need to be vigilant for both delirium and dementia, even in nongeriatric patients. Cognitive disorders are powerful predictors of medical resource consumption and complexity in care-delivery.
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ABSTRACT
INTRODUCTION
