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Correspondence: Address correspondence to Mark E. Kunik, VAMC, 2002 Holcombe (HSR & D152), Houston, TX 77030. E-mail: mkunik{at}bcm.tmc.edu
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Key Words: Mental disorders • Hospitalization • Ambulatory care
Dementia occurs in 5–10% of those over 65 years of age and is known to exact a significant financial cost. In 1991, the total cost of treatment for each person with Alzheimer's disease was estimated to be $174,000 (Ernst & Hay, 1994). The costs of Alzheimer's disease exceed those of cancer and coronary artery disease (National Foundation for Brain Research, 1992). Patients with dementia use 70% more health services (Richards, Shepherd, Crismon, Snyder, & Jermain, 2000) and cost managed care organization 50% more to care for than age matched controls (Gutterman, Markowitz, Lewis, & Fillit, 1999). With an aging population, the economic and social impact will likely increase. Further understanding of cost determinants is important to guide future cost-effective health care policy. Possible significant determinants of health care cost are the behavioral symptoms and psychiatric disturbances (BSPD; i.e., agitation, aggression, depression, anxiety, and psychosis) that occur in more than 50% of dementia patients (Lyketsos et al., 2000; Tariot & Blazina, 1994).
BSPD play a large role in caregiver burden and the decision to ultimately place patients in nursing homes (Bianchetti et al., 1995; C. A. Cohen et al., 1993), contributing much to the cost of Alzheimer's disease. BSPD also contribute to the disability associated with dementia (Forsell & Winblad, 1998). In addition, behavioral disturbances can precipitate hospitalization in an acute setting, thus adding to the cost of care.
In a recent study of health care utilization, older veterans who were discharged from a hospital with depression, dementia, or both were compared (Kales et al., 1999). Those with coexisting depression and dementia had more psychiatric inpatient and total (medical and psychiatric) inpatient days than the other two groups, and more medical inpatient days than the depression-alone group. However, the group with comorbid dementia and depression used less outpatient services than the other two groups. This study was limited by its inclusion of only discharged patients, which excluded most dementia patients because only a minority of dementia patients are hospitalized. In addition, patients with coexisting dementia and depression comprised only 5% of the dementia patients, a lower percentage than that reported in the literature. To date, no other study has attempted to assess the degree to which psychiatric comorbidity in patients with dementia is associated with health care utilization. Our retrospective cohort study used Veterans Affairs (VA) databases to examine health service use patterns in dementia patients with psychiatric comorbidity. We hypothesized that patients with dementia and psychiatric comorbidity compared with demented patients without psychiatric comorbidity would have higher medical and psychiatric health service use.
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Selection of Cohort
All VA beneficiaries seen at the Houston Veterans Affairs Medical Center (VAMC) with a diagnosis of dementia were obtained from the 1997 VA Outpatient Clinic File (OPC). The OPC includes outpatient contacts, diagnoses, procedures, age, race, gender, marital status, and income for all veterans treated at the Houston VA in 1997. The following ICD-9-CM dementia codes were used to select the study cohort from these computerized databases: 290 (dementia of the Alzheimer's type), 290.4 (vascular dementia), 291.2 (alcohol-induced persisting dementia), 292.82 (other substance-induced persisting dementia), 294.1 (dementia due to other general medical conditions), and 294.8 (dementia not otherwise specified). Subjects were entered into the study cohort on the date of their first 1997 visit in which they received a diagnosis of dementia. Those patients who died within 30 days of study entry were excluded from the sample because of their characteristically high service differentiates them from the remainder of the sample.
Procedure
The cohort of dementia patients was divided into those who had psychiatric comorbidity and those who did not. Analyses of psychiatric comorbidity were conducted using two different definitions: (a) a diagnosis of dementia with either a 1997 comorbid psychiatric diagnosis (ICD-9-CM code in the 290–319 range), or depression and/or delusions (ICD-9-CM: 290.12, 290.13, 290.20, 290.21, 290.42, or 290.43); or (b) a 1997 diagnosis of dementia with either inpatient or outpatient psychiatric contacts at the Houston VAMC. Results using the latter definition were nearly identical to those using the former; therefore, only the results of the analyses using the ICD-9-CM psychiatric comorbid definition are reported.
The primary dependent measure was amount of Houston VA health service use from study entry until the end of fiscal year 1999 or until death. Average enrollment time in the study was 22 months. Service use was collected from VA databases and included inpatient bed days (medical/surgical and psychiatric, excluding long-term care days) and number of outpatient clinic visits (medical/surgical and psychiatric). There has been some indication in the literature that comorbidity may be associated with shortened life expectancy in dementia patients (Kales et al., 1999; Moritz, Fox, Luscombe, & Kraemer, 1997). We were thus concerned that patient number of days in this study, which constitutes the risk period for health service use (time from study entry until the end of fiscal year 1999 or death), might differ between the two groups. Given the nonnormal distribution of the data, we used a Mann-Whitney U test to evaluate possible differences in number of days in study and found the sum of ranks (comorbidity present = 138,417; comorbidity absent = 235,263) were significantly different (Mann-Whitney U = 75,933, p <.05). Therefore, we controlled for days in study when conducting regression analyses to investigate the contribution of psychiatric comorbidity to service use (see following Data Analysis section).
Risk adjustment across groups was accomplished by controlling the variables of age, medical comorbidity, gender, ethnicity, and marital status. We used the OPC diagnoses to control for medical comorbidities (Kuykendall & Johnson, 1995; Luft et al., 1990). Each of the following eight dichotomously-scored body system categories was coded positively if any comorbidities belonging to that body system were recorded: endocrine, hematologic, neurologic, cardiologic, pulmonary, gastrointestinal, genitourinary, and rheumatology.
Data Analysis
The relationship between psychiatric comorbidity and health service utilization was first explored by conducting Mann-Whitney U tests between those with and without additional psychiatric diagnoses. The nonparametric Mann-Whitney U test was used because the data had a nonnormal distribution with a large number of participants having no service use. The Scheffé adjustment for multiple comparisons was used, resulting in an alpha level of.01.
The effect of psychiatric comorbidity on health service utilization was further explored using logistic regression models. A separate model was constructed for each of the four health service use dependent variables (medical bed days of care per patient year, medical outpatient visits per patient year, psychiatric bed days of care per patient year, and psychiatric outpatient visits per patient year). For each model, days in study, age, gender, ethnicity, marital status, and medical comorbidity were entered first as covariates. Psychiatric comorbidity was then entered on the second step as a dichotomous variable (psychiatric comorbidity present vs. absent).
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2(1, N = 276) = 5.09, p <.05; 2(1, N = 209) = 5.18, p <.05; and 2(1, N = 34) = 4.05, p <.05, respectively.
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Discussion |
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The association of age and gender with psychiatric comorbidity in dementia patients has been inconsistent (Rao & Lyketsos, 1998; Wragg & Jeste, 1989). Several studies have shown that psychiatric comorbidity increases with age and severity of illness (Hirono et al., 1998; Kotrla, Chacko, Harper, & Doody, 1995), whereas others have not found an association (Gormley & Rizwan, 1998; Migliorelli et al., 1995). Our finding that patients with psychiatric comorbidity were younger may reflect a diagnosis bias; patients with psychiatric comorbidity receive a diagnosis of dementia earlier in the disease process because they are more likely to be receiving intensive clinical care. Other studies have found increased aggression and other behavioral disturbances to occur more often in male patients with dementia (Eastley & Wilcock, 1997; Lyketsos et al., 2000). In our study, men may have been diagnosed more often with psychiatric comorbidity because their behavioral symptoms are more severe and more likely to necessitate clinical care.
The association of marital status and ethnicity with psychiatric comorbidity has received little attention in the literature. Caregivers of nonmarried patients may be more likely to be distant relatives or to not be related and thus have less familiarity with the patient's likes and dislikes and optimal ways of interacting with the patient. When compared with older divorced adults, married adults function better (Schone & Weinick, 1998). Perhaps caregivers of nonmarried patients have less tolerance for psychiatric comorbidity and therefore are more likely to quickly refer them for treatment rather than attempt to manage the problems themselves.
When compared with dementia patients without psychiatric comorbidity, we found that demented veterans with psychiatric comorbidity have more medical inpatient service use, and more psychiatric service inpatient and outpatient use, even after adjusting for the effects of demographic and medical comorbidity differences. In comparison, Kales and colleagues' (1999) 2-year follow-up of veterans admitted for dementia, depression, or both found that demented depressed patients had only increased inpatient psychiatric service use when compared with the other two groups. Regarding outpatient psychiatric service use and inpatient medical use, the depressed-only group was higher on the former and lower on the latter when compared with the demented-depressed group, whereas the demented-only group was similar to the demented-depressed group on the two variables. The differences between this study and ours likely reflect differences in cohort definition. Their cohorts were defined by an inpatient stay, resulting in the inclusion of only a very small portion of all patients who have dementia only or dementia and depression. In addition, we examined patients with any psychiatric comorbidity (as opposed to Kales and colleagues' inclusion of only depressed patients), which resulted in the inclusion of a substantial number of patients with other psychiatric diagnoses that have been associated with high service use in nondemented populations (e.g., psychosis, anxiety, and alcohol use; de Beurs et al., 1999; Robert, Blow, & Bingham, 2000). Similar to Kales and colleagues, examination of the odds ratios from the logistic regression models indicates that psychiatric comorbidity has a much stronger effect on the likelihood of psychiatric service use as compared with medical service use. This finding may reflect the multidisciplinary needs of these patients.
This study's limitations include the fact that we relied on administrative database diagnosis and did not validate them by examining the patients. Generally, only dementia that is relatively severe is coded, and thus our cohort probably represents the more severe end of the disease spectrum. It may be that psychiatric comorbidity is less prevalent in people with milder dementia. In addition, problems exist with making cause/effect arguments from retrospective cohort studies. For instance, patients who more frequently interface with the health care system are more likely to obtain diagnoses, including psychiatric diagnoses. Our health service use measurement is limited to the health service use of veterans who use the VA healthcare system. Our utilization figures are underestimates to the extent that we could not capture our cohort members' use of non-VA services. Finally, our findings may not be generalizable to all veterans or the general population. Generally, veterans who use the VA healthcare system are more likely to be male, indigent, and more medically ill than veterans who do not use the VA or the general population.
The complicated social and neuropsychiatric problems of dementia patients with psychiatric comorbidity challenge providers, caregivers, and health care administrators. These patients encounter the health care system through multiple and inconsistent providers (primary care, neurologists, psychiatrists) and health care institutions (outpatient care, medical or psychiatric hospitalization, partial hospitalization, adult day care, long-term care facilities). The resulting fragmented health care of these patients may affect the costs and quality of care. Further understanding of the current health service use of dementia patients with psychiatric comorbidity may help to establish a framework for considering change in the current system of care.
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This research is based on work supported by the Office of Research and Development, Health Services R&D Service, Department of Veterans Affairs. Mark Kuebeler, MS, aided in the statistical analysis. 
1Houston Center for Quality of Care and Utilization Studies, Houston Veterans Affairs Medical Center, TX.
2Veterans Affairs South Central Mental Illness Research, Education, and Clinical Center (MIRECC), Houston, TX.
3Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, TX.
4Department of Medicine, Baylor College of Medicine, Houston, TX.
5Psychiatry and Behavioral Sciences Department, University of Arkansas for Medical Sciences, Little Rock, AR.
6Center for Mental Health and Outcomes Research, Central Arkansas Veterans Healthcare System, Little Rock, AR.
Received for publication March 25, 2002. Accepted for publication July 5, 2002.
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This article has been cited by other articles:
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  M. E. Kunik, J. A. Cully, A. L. Snow, J. Souchek, G. Sullivan, and C. M. Ashton Treatable Comorbid Conditions and Use of VA Health Care Services Among Patients With Dementia Psychiatr Serv, January 1, 2005; 56(1): 70 - 75. [Abstract] [Full Text] [PDF]
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