{Reprinted fromVolume 10, Number 1, February 2007

( Vagus Nerve Stimulation Therapy forPharmacoresistant Epilepsy:

Effect on Health Care Utilization

Allan L. Bernstein, Howard Barkan, and Terry Hess

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BehaviorELSEVIER Epilepsy & Behavior 10 (2007) 134-137

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Vagus nerve stimulation therapy for pharmacoresistant epilepsy:Effect on health care utilization *

Allan L. Bernstein a,b,*, Howard Barkan ", Terry Hess ba Department of Neurology, Kaiser Permanente Medical Center, 401 Bicentennial Way, Santa Rosa, CA, USA

b Clinical Research Center of the North Bay, Santa Rosa, CA, USA

Received 23 June 2006; revised 8 September 2006;1!ccepted 27 September 2006Available online 3 November 2006

Abstract

We retrospectively analyzed the effects of vagus nerve stimulation (VNS) therapy on utilization of medical services by 138patients in alarge staff-model health maintenance organization. We compared average quarterly rates for 12 months before device implantation withquarterly rates during 48 months of follow-up. Wilcoxon matched-pairs signed-ranks tests comparing pre-VNS with post-VNS utiliza-tion rates showed statistically significant reductions in numbers of emergency department visits, hospitalizations, and hospital lengths ofstay, beginning with the first quarter after implantation (P < 0.05 for all post-implantation quarters for these three aspects). For the firsttwo quarters after implantation, the average number of outpatient visits was significantly greater than the pre-implant quarterly average(quarter 1: P < 0.0001; quarter 2: P = 0.0067), but the average was 12.2% less by the fourth quarter of the first year after implantationand significantly less beginning with the first quarter of the second year (P = 0.0017) and continuing through the end of the study(P < 0.0001 for all subsequent quarters). A comparison of time spent on epilepsy-related tasks during the year before implantation withthe year after implantation also revealed significant decreases in the average number of days on which patients could not work because ofhealth-related concerns, from 3..67 to 1.04days (P = 0.002, paired Student's t test) and the average time spent caring for health problems,from 352.6 to 136.1minutes per week (P < 0.001). VNS therapy had a positive effecton both the utilization of health care services and thetime spent on epilepsy-related tasks for these patients with pharmacoresistant epilepsy. . . 2006 Elsevier Inc. All rights reserved.

Keywords: Vagus nerve stimulation therapy; Epilepsy; Utilization; Pharmacoresistant

1. Introduction

We studied the effect of vagus nerve stimulation (VNS)therapy on the utilization of medical services by a consec-utive surgical series in Kaiser Permanente, a largestaff-model health maintenance organization (HMO) inNorthern California. To our knowledge, this endeavor isthe first utilization study of VNS therapy conducted inthe United States, although several cost studies fromEurope, the United Kingdom, and Canada have beenpublished [1-8]. .

'" Cyberonics, Inc supported this research through an unrestricted grant. Corresponding author. Fax: +I 707 571 4858.E-mail address: Allan.L.Bemstein@kp.org (A.L. Bernstein).

1525-5050/$ - see front matter 2006 Elsevier Inc. All rights reserved.doi: I0.1016/j.yebeh.2006.09 .014

2. Methods

We retrospectively calculated the utilization of all outpatient visits,emergency department visits, hospital lengths of stay, and number of hos-pital admissions, regardless of whether the utilization was related to epi-lepsy, for patients implanted with the VNS therapy device (Cyberonics,Inc; Houston, TX, USA). We compared the average quarterly utilizationfor the 12months before implantation (pre-VNS) with quarterly rates forthe 48 months afterward (post-VNS). Utilization during the month ofimplantation was not included in the analysis. We performed separateanalyses of the frequency of outpatient department visits, frequency ofemergency department visits, hospital lengths of stay, and number of hos-pital admissions. Treating physicians prescribed VNS according to clinicaljudgment. All implantations were performed at one of two medicalcenters, and patients were returned to their treating neurologists.

A separate analysis of time spent on health-related activities compareddata that were collected during telephone interviews with the patients ortheir earegivers. The interviewer asked these persons how much time

A.L Bernstein et al. / Epilepsy & Behaoior la (2007) 134-137

had been spent performing health-related activities, as well as how manydays they had not been able to work because of health-related concerns,during the year before and the year after implantation with the VNSdevice.

Patients were not screened for any particular demographic variable.Data were available for 140 patients who had been implanted with theVNS device, but 2 patients who were considered outliers were excludedfrom the analysis. One of the outliers incurred high utilization related toa catastrophic motor vehicle crash, and the other outlier had an extendedhospitalization unrelated to epilepsy. A third patient incurred high utiliza-tion related to epilepsy and comorbid conditions. To illustrate the effect ofhigh utilization by a single patient, analyses were computed and graphedwith (/1 = 138) and without (/1 = 137) the utilization of this third patient.

In addition to compiling summary statistics, we used the Wilcoxonmatched-pairs signed-ranks test to compare pre-VNS (the quarterly aver-age during the year before implantation with the VNS device) outpatientvisits, emergency room visits, hospital lengths of stay, and number of hos-pital admissions with quarterly utilization of the same items for the 48months after implantation of the VNS device. Differences from baseline(pre-VNS) were used in the statistical significance tests; however, resultsare presented graphically as percentage change in mean values from base-line to provide a more intuitive appreciation of the time trends.

We used a paired Student I test to compare the amount of time spentperforming health care-related activities and days on which patients couldnot work because of health-related reasons during the year before thepatient was implanted and the year afterward. A P value ";0.05 was con"sidered significant. This study is an initial exploration using a surgical ser-ies design; therefore, statistical analyses were not corrected for multiplecomparisons. The Institutional Review Board of the Kaiser FoundationResearch Institute approved this study.

3. Results

3.1. Demographics

Of the 140 patients who were implanted, 73 (52.1%)were females and 67 (47.9%) were males. Average age atimplantation was 30.2 16.9 years (range 3-81 years).

3.2. Utilization

During the year before implantation, the number of out-patient visits per patient per quarter (n = 138) ranged fromo to 20, with the mean number of visits per patient perquarter increasing from 3.0 3.4 (median 2.0, range0-18) during the first quarter to 4.3 3.5 (median 3.5,range 0-20) during the fourth quarter, just before implan-tation of the VNS device (see Appendix A). For the firsttwo quarters after implantation, the outpatient visit ratewas significantly greater than pre-VNS, with a mean of7.2 2.9 (median 7.0, range 2.0-20.0), an increase of103.7% over pre-VNS (P < 0.0001, Wilcoxon) visits duringthe first quarter; a mean of 4.2 3.2 (median 3.0, range 0-18), an increase of 19.4% over pre-VNS (P = 0.0067) dur-ing the second quarter; a mean of 3.6 2.8 (median 3.0,range 0-12), an increase of 3.2% over pre-VNS(P = 0.7014, not statistically significant) during the thirdquarter. During the fourth quarter after implantation, theoutpatient visit rate was less than that pre-VNS, with a meanof 3.1 2.9 (median 2.0, range 0-14), a decrease of 12.2%(P = 0.0516, not statistically significant). Beginning with

135

the first quarter of the second year after implantation, theaverage number of quarterly outpatient visits was signifi-cantly less than pre-VNS, with a mean of2.9 3.1 (median2.0, range 0-20), a decrease of 16.3% (P = 0.0017). For theremaining quarters of the study, the average number ofoutpatient visits per quarter was significantly less than thatpre-VNS (P < 0.0001) (Fig. 1).

During each of the 16 quarters after implantation, therate of emergency department visits (Fig. 2), hospitallengths of stay (Fig. 3), and number of hospital admissions(Fig. 4) per quarter were significantly less than those pre-VNS. To illustrate the influence of a single patient withgreater utilization than the other patients, each graphshows utilization by 138 patients, which includes the

. "patient with greater utilization, and by 137 patients, whichexcludes the patient.

Outpatient Visits

150

\-, ----.... -~ ~ ~~ -----

'" 100z:::-f. 50E~.,'"

136

Hospital Length of Stay

A.L. Bernstein et al. / Epilepsy & Behaoior la (2007) 134-137

0060

I -i',, ,

I , \,/\ fA .,.,

r-: A. I \ ij -, \/ ">< \''i \ Y ~./ \/ ~..

'"~ 40et 20i 0o~ 20~o -40~ .soc,

00-100

2 5 6 7 8 9 10 11 12 13 14 15 16Quarter Post-VNS

Fig. 3. Percentage change in mean hospital lengths of stay per quarterfrom pre-VNS through 4 years of VNS therapy. To illustrate the effect of asingle patient with high utilization, the line denoting n = 138 includes allpatients in the analysis, and the line denoting n = 137 excludes the patientwith high utilization.

Hospital Admits

o-10

'"~ -20e -30c,:: -40EGO -SO'""~ -600

-TOiD!: -80GOc,

90-100

r--:,I \I \

F' ...:::::-., jf

A.L. Bernstein et al. / Epilepsy & Behauior 10 (2007) 134-137

monetary exchange rates and inflation, but utilization datacan be applied to a multitude of health care settings amongwhich costs and charges may vary considerably for thesame procedure or item. Because the patients enrolled inthe Northern California Kaiser system are representativeof the socioeconomic makeup of the community exceptfor the highest and lowest levels [10], investigators can befurther assured of the suitability of these data.

Limitations of this study include the retrospectivedesign, the lack of a contemporaneous control group withpharmacoresistant epilepsy, and the possibility that theimpending implantation could have contributed to thenumber of outpatient visits during the pre-implant year.On the other hand, this study has two major strengths:the well-documented quarterly changes in utilization ofthe largest number of patients over the longest periodreported to date, and the ease with which these data canbe applied to a variety of settings. The significantly reducednumbers of emergency department visits, outpatient visits,and hospitalizations, as well as the decreased lengths ofstay in the hospital, are consistent with improved controlof epilepsy. In addition, the significantly decreased timespent on epilepsy-related matters and days missed fromwork further reflect positive changes in the lives of bothcaregivers and persons with epilepsy. In summary, theseresults illustrate a distinctly positive influence of VNS ther-apy on the health careutilization of patients with pharma-coresistant epilepsy.

Acknowledgments

Preparation of this article was supported by an unre-stricted educational grant from Cyberonics, Inc., manufac-turer of the VNS Therapy System, to Kaiser Permanente.Dr. Barkan received compensation from Cyberonics forperforming preliminary data analyses. John AlIen, Ph.D.,and Amara Jayewardene, M.S., employees of Cyberonics,performed the statistical analyses presented in this article.Susan E. Siefert, ELS, CBC, also of Cyberonics, assisted

137

with the development of the article. The authors main-tained complete control over the direction and content ofthis article.

Appendix A. Supplementary data

Supplementary data associated with this article can befound, in the online version, at doi:lO.lOI6/j.yebeh.006.09.014.

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