Copyright ª Blackwell Munksgaard 2002 Bipolar Disorders 2002: 4: 398–405

BIPOLAR DISORDERS ISSN 1398-5647

Original Article

Health care utilization and costs among privately insured patients with bipolar I disorder Bryant-Comstock L, Stender M, Devercelli G. Health care utilization and costs among privately insured patients with bipolar I disorder. Bipolar Disord 2002: 4: 398–405. ª Blackwell Munksgaard, 2002 Objective: This study examined health care resource utilization and direct health care costs among patients diagnosed with bipolar I disorder in a privately insured population. Methods: Health care claims data for 2883 patients with a primary diagnosis of bipolar disorder were compared over a 1-year period (1997) with claims data for 2883 randomly selected, age- and sex-matched, nonbipolar patients, all covered under the same large private insurer in USA. Resource use (i.e. original and refill pharmaceutical dispensing, medical and procedural services received, inpatient hospitalization, outpatient services, physician visits and emergency room treatment) and their costs are described overall, as well as by bipolar disorder diagnosis (based on ICD-9 codes) and type of care (i.e. mental health versus non-mental health). Results: Bipolar patients utilized nearly three to four times the health care resources and incurred over four times greater costs per patient compared with the non-bipolar group during the 1-year period ($7663 versus $1962). Inpatient care (hospitalizations) accounted for the greatest disparity between groups, as it was the single-most costly resource in the bipolar group ($2779 versus $398). Patients with bipolar depression (among the single bipolar diagnostic categories of mixed, manic or depressed) incurred the highest health care costs. While mental health care cost was a significant component of total cost in the bipolar group, it accounted for only 22% of the total per-patient cost; in comparison, it accounted for only 6% of the total per-patient cost in the non-bipolar group. Conclusion: Treatment of bipolar disorder, particularly inpatient care, is costly to patients and health insurers. Further study is needed to find ways to reduce the overall cost of managing these patients without jeopardizing patient care.

The economic burden of bipolar disorder is substantial. Bipolar disorder is one of the 10 leading causes of disability worldwide and is projected to remain so through the second decade of the twenty-first century (1, 2). In 1991, the most recent year of comprehensive study, the direct cost of bipolar disorder in USA was estimated to be $7 billion (3).

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Lynda Bryant-Comstocka, Monika Stenderb and Giovanna Devercellic a

GlaxoSmithKline Research and Development, Global Health Outcomes, Research Triangle Park, NC, USA, bGlaxoSmithKline Research and Development, Worldwide Epidemiology, Greenford, Middlesex, UK, cBayer Corporation Pharmaceutical Division, Health Economics and Outcomes Research, West Haven, CT, USA

Key words: bipolar disorder – cost of care – health economics – health care utilization – pharmacoeconomics Received 17 January 2001, revised and accepted for publication 19 July 2002 Corresponding author: Lynda Bryant-Comstock, GlaxoSmithKline, PO Box 13398, Research Triangle Park, NC 27709, USA. Fax: (919) 483-3096; e-mail: [email protected]

As noted by Keck and colleagues (4), bipolar disorder is costly by nature. It is a relatively common illness, with an estimated prevalence of 0.8–1.6% in USA (5, 6) and 0.3–1.5% world-wide (7). Mean age at onset is 21 years (8), and between 80 and 90% of people with an initial episode have recurrences (9). Among untreated patients, the mean lifetime number of diagnosable manic and

Direct cost of bipolar disorder depressive episodes is nine (range: 2–20+) (10). Progressive functional deterioration is common between episodes, and treatment response and prognosis may worsen with each recurrence (11– 13). According to the Epidemiologic Catchment Area (ECA) study, only about 55% of people who have bipolar disorder actually receive treatment for it in a given year (14). Data from the US National Institute of Mental Health are less encouraging, suggesting only about a third of sufferers seek treatment (15). A 1993 survey of members of the National Depressive and Manic– Depressive Association (NDMDA) (16) found that an average of 5 years passed between the initial bipolar episode and the patient’s seeking care for bipolar disorder; 36% did not seek care for 10 years; and the correct diagnosis of bipolar disorder was not made, on average, until 8 years after the patient first sought care. Under-treatment of bipolar disorder is an important cost factor because many of these patients could eventually be successfully managed (17), and successful treatment can reduce cost. It has been estimated, for example, that $1.28 billion in indirect costs and $2.88 billion in direct medical costs were saved in USA alone during the first decade of lithium therapy (1969–79) (18) and although treatment options for bipolar disorder remain limited, the addition of antidepressants, anticonvulsants, and antipsychotics has improved the efficacy and tolerability of pharmacotherapy. While it is known that bipolar disorder is costly, there are limited data available on the specific cost components of bipolar disorder. Such information is needed to ensure rational provision of health care resources, identify areas where cost-savings might be possible, and guide further research. Accurately characterizing the use and cost of insured health care resources is an important first step. In the present study, we describe the use and cost of insured health care resources in a clinically diagnosed bipolar patient population. Methods

This study was a retrospective cross-sectional analysis of electronic health-insurance claims over a 1-year period (1997) from a large insurer in the north-eastern USA. The database included approximately 2.7 million patients represented by 83 different insurance plans. More than half the patients were served by some form of managed care and all were private insurance claimants. For comparative purposes, health care utilization and cost data from patients with bipolar I disorder

were age- and sex-matched with claimants who did not have a diagnosis of bipolar disorder (nonbipolar group). Patient confidentiality was observed and protected throughout the conduct of this study. Data were extracted in aggregate form and no patient identifiers were included. Patients were between 18 and 64 years of age, inclusive, on or before July 1, 1997. (The decision to use this age cut-off was based on the premise that many patients transfer from managed care health plans to Medicare at age 65, and therefore, those remaining in such plans would not be representative of the general over-65 population.) Patients with Medicare Supplement insurance were also excluded, as such patients were not part of the database and could not be adequately tracked. To ensure an adequate enrollment period that would allow capture of data from a representative population of patients with bipolar disorder, patients had to be insured, with prescription coverage, for the full calendar year of 1997 and the last 90 days of 1996. Gaps in enrollment could not exceed 30 days in 1997 (i.e. the minimum allowable number of days enrolled in 1997 was 335). Patients were required to have a primary diagnosis of bipolar disorder (International Classification of Diseases, 9th Revision, Clinical Modification) (i.e. ICD-9 codes 296.0–296.8) and at least two outpatient service records from different days in 1997 listing that diagnosis. While the latter requirement (i.e. two records with bipolar ICD-9 codes) may have resulted in the failure to identify some bipolar disorder cases, the more conservative approach was taken in an attempt to avoid inclusion of misdiagnosed patients, as it was thought that having two separate records with a bipolar code would serve as a confirmation of the diagnosis. The bipolar codes and diagnoses are shown in Table 1. In addition to the six bipolar categories corresponding to the ICD-9 codes, two multicode categories (i.e. 2 and 3+) were included to allow for tracking of resources ⁄ costs among patients who had more than one diagnostic code on claims during the year. Additionally, patients with epilepsy (ICD-9 345) currently receiving an anticonvulsant were excluded, as it was not possible to determine whether the anti-epileptic medication was for the treatment of bipolar disorder or epilepsy. The use and cost of medical encounters, prescription drug dispensing, and laboratory ⁄ diagnostic services were analyzed according to care setting, bipolar diagnostic category, and type of care (mental health ⁄ non-mental health). Medical encounters were identified from outpatient claims

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Bryant-Comstock et al. Table 1. Bipolar ICD-9 codes and diagnoses Bipolar category

ICD-9 code

Differential diagnosis

Single ⁄ recurrent

296.0 296.1 296.4 296.5 296.6 296.7 296.8

Manic disorder, single episode Manic disorder, recurrent episodes Bipolar affective disorder, manic Bipolar affective disorder, depressed Bipolar affective disorder, mixed Bipolar affective disorder, unspecified Manic-depressive psychosis, other and unspecified Any two of the codes above or 296.2 (major depressive disorder, single episode) or 296.3 (major depressive disorder, recurrent) with any other bipolar code Any three or more bipolar codes, or 296.2 or 296.3 with two or more other bipolar codes

Mania Depression Mixed Unspecified Psychosis Multi-code 2

Multi-code 3+

and classifications using Current Procedural Terminology (CPT-4) codes. Medical encounters included all such services as preventive medicine and outpatient visits to physicians, as well as physician and non-physician psychotherapeutic care. Each inpatient admission was also considered an encounter. Encounters were primarily classified by care setting (i.e. inpatient, outpatient hospital, physician’s office, emergency room, and other [e.g. home care, long-term care facilities, other outpatient facilities, and independent clinical laboratories]). Encounters were secondarily grouped into 18 general ÔproceduresÕ based on ICD-9 categories (e.g. surgery, medicine, transportation, evaluate ⁄ manage, maternity ⁄ delivery, etc.). Dispensing included new prescriptions and refills. Medications were identified by National Drug Code number and grouped by American Hospital Formulary Service therapeutic category (antidepressants, anticonvulsants, NSAIDs, etc.). Our data analyses are descriptive and thus do not include the statistical significance of intergroup or intragroup differences; the non-bipolar group data are presented only as a reference. Reported costs are averages paid in US dollars in 1997, except where otherwise noted, and include the amount paid by the insurer, the amount paid by the patient (deductible, co-payment, co-insurance), and the cost of co-ordinating benefits. Results

The study population included 2883 men and women with bipolar I disorder (Table 2) and 2883 randomly selected, age- and sex-matched non-bipolar patients. In both groups, the majority of patients were between the ages of 35 and 54 years, and 62% were female. Thirty-three percent of the patients were found to have had at least two medical encounters listing different bipolar ICD-9 codes.

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Table 2. Background characteristics of bipolar group

Patients Age range (years) 18–24 25–34 35–44 45–54 55–64 Bipolar category Single ⁄ recurrent Mania Depression Mixed Unspecified Psychosis Multi-code 2 Multi-code 3+

n (%)

Women (%)

Men (%)

2883 (100)

1796 (62)

1087 (38)

306 430 823 866 458

(11) (15) (29) (29) (16)

181 262 525 540 288

(10) (15) (29) (30) (16)

125 168 298 326 170

(12) (15) (27) (30) (16)

264 285 278 355 347 396 638 320

(9) (10) (10) (12) (12) (14) (22) (11)

178 163 165 205 212 260 409 204

(10) (9) (9) (11) (12) (14) (23) (11)

86 (8) 122 (11) 113 (10) 150 (14) 135 (12) 136 (13) 229 (21) 116 (11)

Resource utilization and costs

Overall. Bipolar patients made more frequent use of health care resources and incurred higher costs across all categories (Table 3). Mean total perpatient cost of health care in 1997 was four times higher in the bipolar group than in the non-bipolar group ($7663 versus $1926). Medical encounters. Medical encounters were approximately four times more frequent and more costly in the bipolar group than in the control group (Table 3). Inpatient encounters (hospital admissions) showed the greatest discrepancy, with a greater frequency and subsequent higher perpatient cost ($2779 versus $398). Inpatient care made up 49% of the cost of medical encounters in the bipolar group and 36% of the total cost of care; in contrast, inpatient care accounted for 28% of the cost of medical encounters and 20% of total cost in the non-bipolar group.

Direct cost of bipolar disorder Table 3. Overall resource utilization: mean per-patient use (Fx) and cost ($)a Bipolar group (n ¼ 2883)

Non-bipolar group (n ¼ 2883)

Ratio (bipolar:non-bipolar) Fx

Resource

Fx

$ (% of total)

Fx

$ (% of total)

Medical encountersb Inpatient Outpatient hospital Physician’s office Emergency room Otherc Dispensing CNS Non-CNS Laboratory ⁄ diagnostic services Laboratory Radiologic ⁄ diagnostic Total cost

17.0 0.7 2.9 12.3 1.0 0.1 29.4 18.3 11.0 15.6

5622 (73) 2779 (36) 1242 (16) 1134 (15) 107 (1) 359 (5) 1413 (19) 964 (13) 449 (6) 628 (8)

4.0 0.1 0.6 3.1 0.2 <0.1 8.1 1.9 6.3 5.8

1399 (71) 398 (20) 473 (24) 392 (20) 23 (1) 112 (6) 363 (19) 83 (4) 280 (14) 201 (10)

4.2 14.0 4.6 4.0 4.3 n ⁄c 3.6 9.8 1.8 2.7

4.0 7.0 2.6 2.9 4.7 3.2 3.9 11.6 1.6 3.1

12.7 2.9

261 (3) 367 (5) 7663 (100)

85 (4) 115 (6) 1962 (100)

2.9 2.0

3.1 3.2 3.9

4.4 1.5

$

Abbreviations: n ⁄ c ¼ not computable. a Costs are reported in US dollers and include the amounts paid by the insurer, the patient (deductible, co-payment, coinsurance), and the co-ordination of benefits. b ÔMedical encountersÕ included such categories as medicine, evaluate ⁄ manage, radiology ⁄ ultrasound, surgery, transportation, and maternity ⁄ delivery. c ÔOtherÕ included long-term care facilities, home care, other outpatient facilities, and independent clinical laboratories.

Dispensing. Bipolar patients received over three times more prescription dispensings, costing nearly four times as much, than did the non-bipolar group (Table 3). Sixty-two percent of all dispensing in the bipolar group was for central nervous system (CNS) drugs compared with 23% in the control group. In terms of cost, the top three categories of CNS drugs dispensed in the bipolar group were antidepressants (39%), anticonvulsants (26%), and antipsychotics (20%); the top three categories of CNS drugs dispensed in the non-bipolar group were antidepressants (45%), anticonvulsants (14%), and non-steroidal anti-inflammatory drugs (13%). Laboratory ⁄ diagnostic services. Compared with the non-bipolar group, laboratory ⁄ diagnostic services were used nearly three times more often by bipolar patients, and they were three times more costly (Table 3). The most frequent laboratory services in the bipolar group were blood count and lithium level determination, while in the nonbipolar group it was blood count and lipid panel. Bipolar diagnostic subgroups

Mean per-patient use and cost of medical encounters were higher in each bipolar diagnostic subgroup compared with the non-bipolar group – overall and when indexed by care setting and type of care (i.e. mental health versus non-mental

health) (Table 4). Mean per-patient use and cost of prescription dispensing were also higher in each bipolar subgroup compared with the non-bipolar group, overall and when indexed by type of dispensing (i.e. CNS drugs versus non-CNS drugs) (Table 5). Mean per-patient cost of dispensing ranged from $1213 in the ÔmanicÕ subgroup to $1750 in the Ôthree or more codesÕ subgroup, compared with $363 in the non-bipolar group. Similarly, mean per-patient use and cost of laboratory ⁄ diagnostic services in the non-bipolar group were lower than in each bipolar subgroup. Mental health care and non-mental health care

In the bipolar group, mental health care accounted for 22% of total cost; non-mental health care accounted for 70%; and the remaining 8% was for laboratory ⁄ diagnostic services (not analyzed by type of care for either group) (Table 6). In the nonbipolar group, mental health care accounted for 6% of total cost; non-mental health care, 84%; and laboratory ⁄ diagnostic services, 10%. As expected, bipolar patients used resources for mental health care more frequently and incurred higher costs than did the non-bipolar group. Overall perpatient cost of mental health care was over 14 times higher in the bipolar group ($1693 versus $118). Twenty-six percent of the per-patient cost of mental health care in the bipolar group ($1693) was

401

Bryant-Comstock et al. Table 4. Medical encounters: mean per-patient use (Fx) and cost ($) by diagnosis, care setting, and type of care Totala

Inpatient

Outpatient hospital

Physician’s office

Emergency room

Mental health

Non-mental health

Diagnosis

Fx

$

Fx

$

Fx

$

Fx

$

Fx

$

Fx

$

Fx

$

Non-bipolar Bipolar Single ⁄ recurrent Mania Depression Mixed Unspecified Psychosis Combination-2 Combination-3+

4.0 17.0 16.9 13.6 16.1 14.1 14.1 16.3 18.7 24.7

1399 5622 5078 4775 5130 3350 4280 4485 6930 10028

0.1 0.7 0.6 0.4 0.7 0.3 0.4 0.6 0.9 1.7

398 2779 2262 2083 2536 1160 1845 1803 3759 6100

0.6 2.9 2.6 2.8 2.5 1.8 2.4 2.0 3.7 4.9

473 1242 1071 1332 1122 855 1129 1080 1403 1839

3.1 12.3 12.4 9.8 12.1 11.3 10.4 12.8 12.9 16.4

392 1134 1208 1045 1078 1057 964 1154 1179 1362

0.2 1.0 1.3 0.6 0.8 0.7 0.9 0.9 1.2 1.6

23 107 130 66 78 73 93 98 128 173

0.4 2.6 3.2 1.6 2.8 1.9 2.9 2.8 2.8 2.9

36 729 555 639 554 263 884 519 822 1525

3.6 14.1 13.4 11.8 13.0 12.1 11.0 13.3 15.6 21.3

1363 4893 4523 4135 4576 3088 3396 3966 6108 8503

a Includes category of ÔOtherÕ (long-term care facilities, home care, other outpatient facilities, and independent clinical laboratories), which accounted for a total mean patient resource use of £0.1.

Table 5. Dispensing (CNS ⁄ non-CNS) and laboratory ⁄ diagnostic services: mean per-patient use (Fx) and cost ($) by diagnosis

Total

Non-bipolar Bipolar Single ⁄ recurrent Mania Depression Mixed Unspecified Psychosis Combination-2 Combination-3+

CNS

Non-CNS

Laboratory

Radiologic ⁄ diagnostic

Fx

$

Fx

$

Fx

$

Fx

$

Fx

$

Fx

$

8.1 29.4 22.7 26.8 29.3 28.0 26.8 28.3 32.7 36.8

363 1413 1300 1213 1493 1292 1274 1399 1496 1750

1.9 18.3 12.7 16.2 18.0 17.1 17.1 16.4 21.2 24.8

83 964 757 766 1027 860 868 923 1052 1352

6.3 11.0 10.0 10.1 11.3 10.9 9.7 11.9 11.6 12.0

280 449 544 448 466 432 406 475 445 398

5.8 15.6 13.3 14.7 12.6 12.4 15.7 14.5 17.8 21.1

201 628 617 610 484 391 501 600 763 946

4.4 12.7 10.0 11.9 10.0 10.2 13.1 11.4 14.8 17.5

85 261 224 216 195 208 246 222 335 368

1.5 2.9 3.3 2.8 2.6 2.3 2.6 3.0 3.0 3.6

115 367 393 394 289 184 255 378 429 578

for inpatient care; the non-bipolar group had no inpatient admissions for mental health care. Bipolar patients also made more frequent use of resources for non-mental health care, and at a higher cost ($5342 versus $1642). Discussion

This study examined health care resource utilization and costs in nearly 3000 privately insured patients with bipolar disorder over a year-long period and is the first to describe in detail the economic burden by type of bipolar disorder (based on ICD-9 codes for bipolar disorder) and type of care, specifically mental health or nonmental health care. The results showed clearly that bipolar disorder is associated with significant health care resource use and expenditures, with an annual per-patient health care cost of approximately $7700, nearly four times that of the nonbipolar group.

402

Total

Simon and Unu¨tzer (19) compared the 6-month use and cost of health care resources between a group of insured bipolar patients (n ¼ 1346) and groups of age- and sex-matched controls. Mean per-patient cost in the bipolar group over the 6 months was approximately $3400 compared with nearly $1500 for the control group of general medical outpatients. The authors attributed the excess cost of bipolar disorder primarily to the greater cost of mental health care, which accounted for 46% of the total health care cost in their bipolar population, compared with just 5% in the general medical outpatient group. Our finding of a nearly fourfold higher cost of health care among bipolar patients cannot be explained solely by higher mental health care costs. In our bipolar group, mental health care accounted for 22% of the total per-patient cost, while non-mental health care accounted for 70% (in the non-bipolar group, mental health care accounted for 6% of per-patient cost).

Direct cost of bipolar disorder Table 6. Mental and non-mental health care: mean per-patient use (Fx) and cost ($)a Bipolar group Fx Mental health care Medical encounters Inpatient Outpatient hospital Physician’s office Emergency room Other Dispensing

2.6 0.1 0.4 1.9 0.1 <0.1 18.3

Subtotal Non-mental health care Medical encounters Inpatient Outpatient hospital Physician’s office Emergency room Other Dispensing

Non-bipolar group

$ (% of total)

729 (43) 432 (26) 123 (7) 121 (7) 14 (1) 38 (2) 964 (57)

Fx

0.4 <0.1 <0.1 0.4 <0.1 <0.1 1.9

1693 (100) 14.3 0.3 2.5 10.4 0.9 <0.1 11.0

4893 (92) 2347 (44) 1120 (21) 1014 (19) 93 (<1) 321 (6) 449 (8)

$ (% of total)

36 (30) 4 (3) 4 (3) 26 (22) 0.2 (0.2) 2 (2) 83 (70) 118 (100)

3.6 <0.1 0.6 2.7 0.2 <0.1 6.3

1363 (83) 393 (24) 469 (29) 367 (22) 23 (1) 111 (7) 280 (17)

Subtotal

5342 (100)

1642 (100)

Total per patient cost

7035

1760

Abbreviations: n ⁄ c ¼ not computable. a Excludes laboratory ⁄ diagnostic services, as data by type of care (mental health versus non-mental health) were unavailable.

The discrepancies between our findings and those of Simon and Unu¨tzer may be partially explained by differences in inclusion criteria, as well as differences in patient populations, resource definitions, and other methodological variables. In the present study, the goal was to identify a population with ÔtrueÕ bipolar disorder and thus we attempted to use the most conservative criteria in defining this condition, which included a primary diagnosis of bipolar disorder using ICD-9 codes, as well as at least two outpatient service records (inpatient, outpatient or emergency room) from different days stating that diagnosis. Simon and Unu¨tzer used much broader diagnostic criteria (i.e. a discharge diagnosis of bipolar disorder, cyclothymia or schizoaffective disorder; any outpatient diagnosis in the bipolar spectrum [could be one or two]; or any filled prescription for a mood stabilizer such as lithium, carbamazepine or valproate that was not associated with a seizure disorder). Additionally, that study tracked patients for a 6-month period within a single managed care setting that covered 450 000 lives, while we have included patients from 83 different plans covering 2.7 million lives over a 12-month period. Because of the longer timeframe and greater patient numbers, the sample population in the present study may better represent the general (commercially insured) population with bipolar disorder. The present study, however, may

have included patients with more advanced or uncontrolled bipolar disorder, which may have required more intensive treatment, resulting in increased mental and non-mental health care coverage and costs. For the purpose of this cost analysis, we felt it necessary to include multicode bipolar diagnostic categories (i.e. 2 and 3+), because it was not possible to allocate a percentage of total costs to each of the individual bipolar diagnoses, as some of the health care resources within the database could not be linked to specific bipolar sub-codes, only to the general bipolar ICD-9 code (i.e. 296). These technical difficulties not withstanding, we felt it was also of interest to discover what percentage of the patients with bipolar disorder had health care claims listing more than one bipolar diagnosis; it is noteworthy that a third of the patients were in this category. Not surprisingly, the patients with three or more unique ICD-9 bipolar diagnostic codes (and therefore at least three distinct medical encounters), were the most frequent users of all health care resources and incurred the highest costs. Greater attention therefore should be focused on patients within the six individual bipolar diagnoses, as these estimates are likely to be more accurate. Among these, patients with bipolar depression used the most health care resources and had the highest per-patient cost of medical encounters and dispensing.

403

Bryant-Comstock et al.

As noted by Griffiths et al., (20) use-and-cost studies based on health insurance records share certain limitations – when you classify patients based on medical resource utilization, the economic differences between groups could be because of the same resources used to define the groups and not to differences in underlying severity of illness suggested by utilization of those resources. In our study, clinical data about the patients and controls were largely missing; we did not have information about disease onset, severity, or treatment history. We used data from a large single insurer in the north-eastern USA; this region is heavily served by HMOs, and costs may be lower than in regions with less HMO penetration. Further, our bipolar patient population may not have been representative of the bipolar population in general. By protocol, we excluded patients with only one bipolar episode on record for 1997, including those with only an initial episode in 1997 (80–90% of whom can be expected to have a recurrence) and those with established disease who had only a single medical encounter during the 1-year study period. Our requirement of two bipolar episodes in a 12-month period may have selected patients with advanced disease or disease of greater than average severity and, thus, greater use and cost of resources. The database also did not include disabled patients on Medicaid or Medicare plans, thus limiting the population to those with managed care or indemnity plans. Despite this limitation of our study, our population remains representative of the general USA population, the majority of whom have some form of group health insurance. The nature of the control population used in these analyses also limits the extent to which conclusions can be made. Follow-up studies should utilize control patients with chronic, relapse–remitting disease profiles. Our study was comprehensive in that it included costs paid by the insurer, cost paid by the patient, and the costs of co-ordinating benefits. Because of the volume of data presented here we are unable to present standard deviations for all of the mean values. These mean data should be treated as representatives of data sets that display variability and thus include values that deviate from the mean. The data presented provides an indication of the cost and resource utilization of bipolar disorder in a patient population and is not necessarily applicable to each individual with a bipolar diagnosis. Despite the inherent limitations of using claims data for use-and-cost research, our work offers fresh perspectives on bipolar disorder and its treatment and may serve as a benchmark for future studies.

404

In conclusion, we have found that patients with bipolar disorder use health care resources more frequently and incur higher health care costs than non-bipolar patients. These data support the notion that the cost of treatment of bipolar disorder remains high, with estimates for inpatient medical encounters highlighting the significant burden that this disease places on the funding of health care. Patients with bipolar diagnoses of depression, in particular, demand considerable health care resources compared with other bipolar diagnoses. Treatment of bipolar disorder, particularly inpatient care, is costly to patients and health insurers. Further study is needed to find ways to reduce the overall cost of managing these patients without jeopardizing patient care. Acknowledgement We would like to thank Rose Mills, MPH for her editorial assistance on this manuscript.

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