FULL-LENGTH ORIGINAL RESEARCH
Why U.S. epilepsy hospital stays rose in 2006 *Vıctor M. C ardenas, †Gustavo C. Rom an, ‡Adriana P erez, and §W. Allen Hauser Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
SUMMARY
rdenas is Vıctor M. Ca an Associate Professor of Epidemiology at the COPH, UAMS, Little Rock, Arkansas.
Objective: We observed a substantial increase in age-adjusted hospitalization rates in the United States National Hospital Discharge Survey data from 1996 to 2010. We aimed to assess reasons for this increase. Methods: The National Hospital Discharge Survey collected data on a national sample of short-term hospital stays in nonfederal hospitals. We determined epilepsy-related discharge diagnoses by age, gender, and region using weighted analysis, and estimated age-adjusted rates and annual percent changes using regression analysis. We also looked at epilepsy as the principal discharge diagnosis in the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project. Results: In the United States, on average, nearly 110,000 more admissions were reported each year with epilepsy as the principal discharge diagnosis in 2006–2010 than in 1996–2005, a 2.7-fold increase in hospitalization rates from epilepsy. During this period, there were more hospitalizations with principal discharge diagnosis of epilepsy not otherwise specified, and among older patients. The number of discharges with seizure not otherwise specified dropped dramatically after 2006, and was more evident among pediatric patients. The age-adjusted rates of hospital stays combining discharges with any mention of epilepsy (345.XX) or seizures unspecified (780.39) in seven discharge diagnoses, were similar in 1996–2005 and 2006–2010. Significance: We postulate that the excess in hospitalizations with epilepsy as first discharge diagnosis in 2006–2010 in the United States was related to the changes in coding in 2006. Any use of U.S. hospital discharge data with epilepsy-related diagnosis after that date will require further validation. KEY WORDS: Epilepsy, Trends, Coding, Hospitalization, Surveillance.
At the outset of our investigation, a preliminary analysis of the United States National Hospital Discharge Survey (NHDS) for 1996–2010 indicated that there was a sharp increase in the rates of hospitalizations from epilepsy, which could signal the emergence of a new etiologic factor. In the Accepted June 3, 2014; Early View publication July 9, 2014. *Department of Epidemiology, College of Public Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas, U.S.A.; †Department of Neurology, Weill Cornell Medical College, Methodist Neurological Institute, Houston, Texas, U.S.A.; ‡Division of Biostatistics, and Michael & Susan Dell, Center for Healthy Living, University of Texas School of Public Health, Austin, Texas, U.S.A.; and §Departments Neurology and Epidemiology, Gertrude H. Sergievsky Center, Columbia University, New York, New York,U.S.A. Address correspondence to Vıctor M. Cardenas, Department of Epidemiology, College of Public Health, University of Arkansas for Medical Sciences, 4301 West Markham, 820, Little Rock, AR 72205, U.S.A. E-mail: [email protected] Wiley Periodicals, Inc. © 2014 International League Against Epilepsy
United States, the West Nile virus epidemic had resulted in more viral neuroinvasive disease than all other arboviruses combined since 1964, a public health concern given the known role of arboviral central nervous system infection in epilepsy.1 We also hypothesized that the increase could be an artifact from changes in coding practices. Hospital discharge data not only provide useful public health surveillance data,2 but are considered one of the most important sources of information in epidemiologic studies, despite their limitations. (Gordis,3 p. 55). Previously, an increasing trend in hospitalizations from epilepsy in the United States had been reported from 1993 to 2008 in the Agency for Healthcare Research and Quality (AHRQ) Healthcare Cost and Utilization Project Nationwide Inpatient Sample (HCUP-NIS).4–7 Simultaneous video–electroencephalography (EEG) for standard recording and telemetry has been available for many years, and inpatient video-EEG telemetry is considered important in candidates for neurosurgical
1347
1348 V. M. C ardenas et al. epilepsy therapy. This procedure has been used with increasing frequency in recent years. In one study, the typical onset of seizures of patients undergoing video-EEG was 2 days.8 To evaluate these possible explanations of the increase we conducted weighted analysis of data available from the NHDS (or National Hospital Discharge Survey), a national sample of short-term stays in nonfederal U.S. hospitals. We specifically examined whether: (1) rates of hospitalization from epilepsy increased over time, (2) there were changes in age distribution of hospitalization for epilepsy, (3) there were changes in epilepsy diagnoses by geographic region, and (4) changes could be explained by increasing use of inpatient video-EEG.
Methods We examined public data files from the NHDS for 1996– 2010. The NHDS is a national probability survey of discharge diagnosis of short-term stay, acute care, general, and pediatric nonfederal hospitals in all 50 states and Washington D.C, conducted since 1965 by the National Center for Health Statistics (NCHS).9 From 1988–2007 there were about 500 short-stay hospitals included in the sample in a given year in the NHDS; however, the number of hospitals was reduced to 239 from 2008 to 2010, and the system was restructured after that time. The sample data are weighted to produce annual estimates generalizable to the entire United States. We identified discharge diagnoses of epilepsy listed as principal discharge diagnosis according to the International Classification of Diseases 9th revision Clinical Modification system (ICD-9-CM) (i.e., ICD-9-CM code 345.XX). We also identified diagnoses of epilepsy in any of the seven fields coding for discharge diagnosis, and looked into changes in the fourth digit, particularly for code 345.9 (epilepsy, unspecified). We also examined discharges coded as ICD-9-CM 780.39 (seizures, unspecified), which, if recurrent, in October 1, 2006, started to be coded as 345.9.10,11 In addition, we assessed changes in the proportion of hospital discharges in the NHDS with any mention of video-EEG (ICD-9-CM code 89.19) in any of the four procedure codes available. We obtained hospitalization rates, age-adjusted to the 2000 Census population, using estimates of the civilian population by year available on the NHDS website.9 We calculated confidence intervals using the Taylor linearization method available in SUDAAN (Research Triangle Institute, Research Triangle Park, NC, U.S.A.) using the Analytic Data Research by Email (ANDRE) interface made available by NCHS.9 We also examined the estimates available to the public from the Agency for Healthcare Research and Quality’s (AHRQ) Healthcare Cost and Utilization Project Nationwide Inpatient Survey (HCUP-NIS), for the 18-year period from 1993 to 2010. Currently HCUP-NIS obtains data from 20% of all U.S. community hospitals. The number of states Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
included in HCUP-NIS increased from 8 in 1988 to 46 in 2011. Weighted analyses were obtained using the query system HCUPnet.12 To better describe the trends in age-adjusted rates within the 15 years examined, we calculated the annual percent change (APC) and average annual percent change (AAPC), a summary trend measure of APCs in the time series.13 We used the National Cancer Institute Joinpoint Regression Program (version 4.0.4; Bethesda, MD, U.S.A.) to identify how the series of age-adjusted rates of hospital stays can be decomposed into time periods (i.e., segments) by identifying breaking points (i.e., joinpoints) by fitting a regression line to the natural logarithm of the rates using calendar year as predictor, and testing whether the slopes were different using a significance level of 0.05.
Results The rates of hospitalizations listing epilepsy (ICD-9-CM 345.XX) as first discharge diagnosis in the NHDS remained stable across the 1996–2005 interval: 20.2 discharges per 100,000 population (95% confidence interval [CI] 15.0–25.3). In 2006–2010, the hospital-stay rates listing epilepsy as first discharge diagnosis in U.S. hospitals had a 2.7fold increase: 54.4 discharges per 100,000 person-years (95% CI 40.6–68.2). Table 1 presents the number of hospitalizations and age-adjusted rates of stays listing epilepsy or seizures by year, the mean number for each of the periods 1996–2005, and 2006–2010, as well as the annual percent change in 1996–2005 and the AAPC for 2006–2010 based on joinpoint regression analyses. There was a sudden increase in discharges from epilepsy as principal discharge diagnosis after 2006, jumping from 62,314 in 2005 to 220,239 discharges by 2010. The discharge rates per year as indicated by the APC was stable in 1996–2005 (i.e., 0.4%), but increased to an AAPC of 24.7% (p < 0.05) in 2006–2010. The estimated number of hospital discharges from unspecified epilepsy (ICD-9-CM 345.9) increased from 11,570 in 2005 to 132,342 in 2010, with average of discharges with such diagnosis of 12,836 in the 1996–2005 period and 89,984 in the 2006–2010 period, a sevenfold increase between the two study periods, and although the APC of hospitalization rates demonstrated little change between 1996 and 2005, the AAPC was 45.8% for epilepsy nonspecified (ICD-9-CM 345.9) was 1.8 times the change in discharges with any form epilepsy (ICD-9-CM 345.XX) in 2006–2010. The number of hospital discharges with the principal diagnosis of unspecified seizures (ICD-9-CM 780.39), decreased from 21,671 in 2005 to 7,503 in 2010. The APC of hospitalization rates showed minimal and not statistically significant decreases in the 1996 to 2005 period ( 2.1%), but the AAPC in 2006–2010 was 20.3% (p < 0.05). Of note, the changes could be identified starting in 2007.
1349 U.S. Epilepsy Hospital Stays Increase in 2006
Table 1. Estimates of hospitalizations and age-adjusted rates of stays per 100,000 persons with epilepsy and seizures diagnoses, United States 1993–2010 HCUP- NIS
NHDS Principal discharge diagnosis
Year 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Mean 1996–2005 APC 1996–2005 2006 2007 2008 2009 2010 Mean 2006–2010 AAPC 2006–2010
Epilepsy (345.X) Number 46,387 48,864 48,345 51,902 46,549 51,066 49,327 54,320 57,738 70,567 54,107
Epilepsy (345.XX)
Epilepsy NOS (345.9)
Seizures NOS (780.39)
Epilepsy (345.XX)
Number
Number
Number
Rate
Number
Rate
58,800 58,280 51,757 51,201 56,079 53,544 52,699 60,189 60,246 62,314 56,511
22.3 21.6 18.9 18.6 20.2 19.1 18.4 20.8 20.6 21.1
14,295 11,757 10,689 11,561 14,041 12,031 13,687 14,692 14,140 11,570 12,846
5.4 4.3 3.9 4.2 5.0 4.3 4.8 5.1 4.8 3.9
0.4 73,146 136,300 170,484 178,891 205,892 152,943
Discharges with any mention in discharge diagnoses of
79,336 145,086 187,610 200,110 220,239 166,476
26.6 43.3 61.9 65.4 71.5 24.7a
27,556 32,843 25,992 23,230 25,378 26,657 25,905 25,771 26,799 21,671 26,180
0.4 23,115 74,854 106,100 113,280 132,342 89,938
7.8 24.9 35.0 37.0 43.0
Rate 10.4 12.1 9.5 8.4 9.1 9.5 9.0 8.9 9.2 7.3
113,018 119,144 109,170 98,811 106,723 98,402 109,389 111,419 105,648 116,147 108,787
2.1 21,536 11,752 7,050 10,680 7,503 11,704
45.8a
7.2 3.9 2.3 3.5 2.4 20.3a
Rate 42.8 44.1 40.0 35.9 38.4 35.0 38.1 38.5 36.1 39.3
Epilepsy NOS (345.9)
Seizures NOS (780.39)
Number
Number
Rate
711,546 739,123 735,928 775,297 745,509 785,106 803,274 852,046 903,805 871,043 792,268
269.5 273.3 269.4 281.4 268.0 279.4 279.8 294.3 309.1 295.1
41,132 44,812 38,690 35,469 42,890 35,941 44,646 44,558 38,417 43,665 41,022
1.8 155,251 441,074 618,988 705,160 740,788 532,252
52.1 146.8 204.4 230.6 240.6 38.8a
Rate 15.6 16.6 14.2 12.9 15.4 12.8 15.5 15.4 13.1 14.8
1.1 75,226 330,087 483,876 561,914 591,608 408,542
25.3 109.9 159.8 183.8 192.2 55.4a
0.6 853,425 653,006 412,784 329,274 322,088 514,115
286.4 217.3 136.3 107.7 104.6 25.4a
Note: if there were no changes in trends, then AAPC equals APC. APC, annual percent change; AAPC, average annual percent change. a p < 0.05. Sources: CDC NCHS, NHD: National Hospital Discharge Survey, Public Use files 1996–2010, and HCUP: Healthcare Cost Utilization Project, Nationwide Inpatient Sample, http://hcupnet.ahrq.gov/HCUPnet.jsp.
The number of discharges with any mention of epilepsy (ICD-9-CM 345.XX) in the seven fields coding for discharge diagnoses changed little in the 1996–2005 time period, but increased by almost fivefold in the 2006–2010 period (i.e., 532,252/108,787). The AAPC in 2006–2010 was 38.8% (p < 0.05). The changes observed in the estimated number of discharges with any mention of unspecified epilepsy (ICD-9-CM 345.9) increased by almost 10fold (i.e., 408,542/41,022), and the AAPC in 2006–2010 was 55.4% (p < 0.05). The total number of discharges with any mention of unspecified seizures (ICD-9-CM 780.39) changed little in the 1996–2005 period, but the decrease in 2006–2010 ( 35.1%, i.e., 278,153/792,268) was statistically significant. Table 2 shows the results of the trend analysis of ageadjusted hospital stays per 100,000, using joinpoint regression. For discharges with epilepsy (ICD-9-CM 345.XX), either as principal discharge diagnosis or as epilepsy unspecified (ICD-9-CM 345.9), there were clearly three distinct segments: the period 1996–2005 without changes in
the rates, and a sudden and statistically significant increase in 2006–2008, followed by a plateau without significant change since 2008. In contrast, the time series of rates for hospital stays with seizures not specified (ICD-9-CM 780.39), as principal discharge diagnosis or any mention of unspecified seizures, had only one statistically significant joinpoint, breaking the series into two segments 1996–2005 and 2006–2010. As shown in Figure 1, the changes were sudden and simultaneous in 2006. The increase in principal discharge diagnosis of any type of epilepsy (ICD-9-CM 345.XX) shown in the series at top of the panel A of Figure 1, representing all types of epilepsy, could be attributed to the increase in diagnoses of epilepsy without any other specification regarding type (ICD-9-CM 345.9). At the same time, the rates of hospital stays with principal discharge diagnoses coded as due to seizures not otherwise specified (ICD-9CM 780.39) dropped from around 10 stays per 100,000 to 2 per 100,000. Panel B of Figure 1, shows that the occurrence of hospitalizations with seizures not otherwise specified Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
1350 V. M. C ardenas et al. Table 2. Trends in age-adjusted rates of hospital stays of epilepsy-related diagnoses in the US, 1996–2010 Discharge Diagnosis
Joinpoints
Time period (segments)
Annual percent change
Epilepsy as principal (ICD-9-CM 345.XX)
2
Unspecified epilepsy as principal (ICD-9-CM 345.9)
2
Seizures NOS as principal (ICD-9-CM 780.39)
1
Any mention of epilepsy (ICD-9-CM 345.XX)
2
Any mention of unspecified epilepsy (ICD-9-CM 345.9)
2
Any mention of seizures NOS (ICD-9-CM 780.39)
1
1996–2005 2005–2008 2008–2010 1996–2005 2005–2008 2008–2010 1996–2004 2004–2010 1996–2005 2005–2008 2008–2010 1996–2005 2005–2008 2008–2010 1996–2006 2006–2010
0.4 48.0a 5.1 3.8 105.3a 3.6 2.1 31.0a 1.8 83.4a 5.0 1.1 137.1a 1.9 0.6 25.4a
a
95% CI 2.5, 1.8 17.2, 86.9 16.8, 32.8 3.8, 3.0 41.3, 198.4 28.7, 50.6 8.3, 4.5 28.0, 11.7 3.6, 0.0 50.4, 123.8 13.9, 28.1 4.0, 1.9 71.5, 227.7 26.3, 40.8 1.2, 2.4 30.6, 19.7
p < 0.05.Source: CDC NCHS, NHDS Public Use files 1996–2010.
Figure 2. Age-specific rates of hospitalization with epilepsy as principal discharge diagnosis between 1996–2005 and 2006–2010. Epilepsia ILAE
Figure 1. Estimates of age-adjusted hospitalization rates with discharge diagnoses of epilepsy and seizure disorders in 1996–2010, United States of America. (A) Principal discharge diagnosis. (B) Any discharge diagnosis. Epilepsia ILAE Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
(ICD-9-CM 780.39) in any of the discharge diagnoses decreased by two thirds from around 300 discharges per 100,000 to 100 per 100,000, whereas the rates of hospital stays with any type of epilepsy (ICD-9-CM 345.XX) in any of the discharge diagnoses increased from
Why U.S. epilepsy hospital stays rose in 2006 *Vıctor M. C ardenas, †Gustavo C. Rom an, ‡Adriana P erez, and §W. Allen Hauser Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
SUMMARY
rdenas is Vıctor M. Ca an Associate Professor of Epidemiology at the COPH, UAMS, Little Rock, Arkansas.
Objective: We observed a substantial increase in age-adjusted hospitalization rates in the United States National Hospital Discharge Survey data from 1996 to 2010. We aimed to assess reasons for this increase. Methods: The National Hospital Discharge Survey collected data on a national sample of short-term hospital stays in nonfederal hospitals. We determined epilepsy-related discharge diagnoses by age, gender, and region using weighted analysis, and estimated age-adjusted rates and annual percent changes using regression analysis. We also looked at epilepsy as the principal discharge diagnosis in the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project. Results: In the United States, on average, nearly 110,000 more admissions were reported each year with epilepsy as the principal discharge diagnosis in 2006–2010 than in 1996–2005, a 2.7-fold increase in hospitalization rates from epilepsy. During this period, there were more hospitalizations with principal discharge diagnosis of epilepsy not otherwise specified, and among older patients. The number of discharges with seizure not otherwise specified dropped dramatically after 2006, and was more evident among pediatric patients. The age-adjusted rates of hospital stays combining discharges with any mention of epilepsy (345.XX) or seizures unspecified (780.39) in seven discharge diagnoses, were similar in 1996–2005 and 2006–2010. Significance: We postulate that the excess in hospitalizations with epilepsy as first discharge diagnosis in 2006–2010 in the United States was related to the changes in coding in 2006. Any use of U.S. hospital discharge data with epilepsy-related diagnosis after that date will require further validation. KEY WORDS: Epilepsy, Trends, Coding, Hospitalization, Surveillance.
At the outset of our investigation, a preliminary analysis of the United States National Hospital Discharge Survey (NHDS) for 1996–2010 indicated that there was a sharp increase in the rates of hospitalizations from epilepsy, which could signal the emergence of a new etiologic factor. In the Accepted June 3, 2014; Early View publication July 9, 2014. *Department of Epidemiology, College of Public Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas, U.S.A.; †Department of Neurology, Weill Cornell Medical College, Methodist Neurological Institute, Houston, Texas, U.S.A.; ‡Division of Biostatistics, and Michael & Susan Dell, Center for Healthy Living, University of Texas School of Public Health, Austin, Texas, U.S.A.; and §Departments Neurology and Epidemiology, Gertrude H. Sergievsky Center, Columbia University, New York, New York,U.S.A. Address correspondence to Vıctor M. Cardenas, Department of Epidemiology, College of Public Health, University of Arkansas for Medical Sciences, 4301 West Markham, 820, Little Rock, AR 72205, U.S.A. E-mail: [email protected] Wiley Periodicals, Inc. © 2014 International League Against Epilepsy
United States, the West Nile virus epidemic had resulted in more viral neuroinvasive disease than all other arboviruses combined since 1964, a public health concern given the known role of arboviral central nervous system infection in epilepsy.1 We also hypothesized that the increase could be an artifact from changes in coding practices. Hospital discharge data not only provide useful public health surveillance data,2 but are considered one of the most important sources of information in epidemiologic studies, despite their limitations. (Gordis,3 p. 55). Previously, an increasing trend in hospitalizations from epilepsy in the United States had been reported from 1993 to 2008 in the Agency for Healthcare Research and Quality (AHRQ) Healthcare Cost and Utilization Project Nationwide Inpatient Sample (HCUP-NIS).4–7 Simultaneous video–electroencephalography (EEG) for standard recording and telemetry has been available for many years, and inpatient video-EEG telemetry is considered important in candidates for neurosurgical
1347
1348 V. M. C ardenas et al. epilepsy therapy. This procedure has been used with increasing frequency in recent years. In one study, the typical onset of seizures of patients undergoing video-EEG was 2 days.8 To evaluate these possible explanations of the increase we conducted weighted analysis of data available from the NHDS (or National Hospital Discharge Survey), a national sample of short-term stays in nonfederal U.S. hospitals. We specifically examined whether: (1) rates of hospitalization from epilepsy increased over time, (2) there were changes in age distribution of hospitalization for epilepsy, (3) there were changes in epilepsy diagnoses by geographic region, and (4) changes could be explained by increasing use of inpatient video-EEG.
Methods We examined public data files from the NHDS for 1996– 2010. The NHDS is a national probability survey of discharge diagnosis of short-term stay, acute care, general, and pediatric nonfederal hospitals in all 50 states and Washington D.C, conducted since 1965 by the National Center for Health Statistics (NCHS).9 From 1988–2007 there were about 500 short-stay hospitals included in the sample in a given year in the NHDS; however, the number of hospitals was reduced to 239 from 2008 to 2010, and the system was restructured after that time. The sample data are weighted to produce annual estimates generalizable to the entire United States. We identified discharge diagnoses of epilepsy listed as principal discharge diagnosis according to the International Classification of Diseases 9th revision Clinical Modification system (ICD-9-CM) (i.e., ICD-9-CM code 345.XX). We also identified diagnoses of epilepsy in any of the seven fields coding for discharge diagnosis, and looked into changes in the fourth digit, particularly for code 345.9 (epilepsy, unspecified). We also examined discharges coded as ICD-9-CM 780.39 (seizures, unspecified), which, if recurrent, in October 1, 2006, started to be coded as 345.9.10,11 In addition, we assessed changes in the proportion of hospital discharges in the NHDS with any mention of video-EEG (ICD-9-CM code 89.19) in any of the four procedure codes available. We obtained hospitalization rates, age-adjusted to the 2000 Census population, using estimates of the civilian population by year available on the NHDS website.9 We calculated confidence intervals using the Taylor linearization method available in SUDAAN (Research Triangle Institute, Research Triangle Park, NC, U.S.A.) using the Analytic Data Research by Email (ANDRE) interface made available by NCHS.9 We also examined the estimates available to the public from the Agency for Healthcare Research and Quality’s (AHRQ) Healthcare Cost and Utilization Project Nationwide Inpatient Survey (HCUP-NIS), for the 18-year period from 1993 to 2010. Currently HCUP-NIS obtains data from 20% of all U.S. community hospitals. The number of states Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
included in HCUP-NIS increased from 8 in 1988 to 46 in 2011. Weighted analyses were obtained using the query system HCUPnet.12 To better describe the trends in age-adjusted rates within the 15 years examined, we calculated the annual percent change (APC) and average annual percent change (AAPC), a summary trend measure of APCs in the time series.13 We used the National Cancer Institute Joinpoint Regression Program (version 4.0.4; Bethesda, MD, U.S.A.) to identify how the series of age-adjusted rates of hospital stays can be decomposed into time periods (i.e., segments) by identifying breaking points (i.e., joinpoints) by fitting a regression line to the natural logarithm of the rates using calendar year as predictor, and testing whether the slopes were different using a significance level of 0.05.
Results The rates of hospitalizations listing epilepsy (ICD-9-CM 345.XX) as first discharge diagnosis in the NHDS remained stable across the 1996–2005 interval: 20.2 discharges per 100,000 population (95% confidence interval [CI] 15.0–25.3). In 2006–2010, the hospital-stay rates listing epilepsy as first discharge diagnosis in U.S. hospitals had a 2.7fold increase: 54.4 discharges per 100,000 person-years (95% CI 40.6–68.2). Table 1 presents the number of hospitalizations and age-adjusted rates of stays listing epilepsy or seizures by year, the mean number for each of the periods 1996–2005, and 2006–2010, as well as the annual percent change in 1996–2005 and the AAPC for 2006–2010 based on joinpoint regression analyses. There was a sudden increase in discharges from epilepsy as principal discharge diagnosis after 2006, jumping from 62,314 in 2005 to 220,239 discharges by 2010. The discharge rates per year as indicated by the APC was stable in 1996–2005 (i.e., 0.4%), but increased to an AAPC of 24.7% (p < 0.05) in 2006–2010. The estimated number of hospital discharges from unspecified epilepsy (ICD-9-CM 345.9) increased from 11,570 in 2005 to 132,342 in 2010, with average of discharges with such diagnosis of 12,836 in the 1996–2005 period and 89,984 in the 2006–2010 period, a sevenfold increase between the two study periods, and although the APC of hospitalization rates demonstrated little change between 1996 and 2005, the AAPC was 45.8% for epilepsy nonspecified (ICD-9-CM 345.9) was 1.8 times the change in discharges with any form epilepsy (ICD-9-CM 345.XX) in 2006–2010. The number of hospital discharges with the principal diagnosis of unspecified seizures (ICD-9-CM 780.39), decreased from 21,671 in 2005 to 7,503 in 2010. The APC of hospitalization rates showed minimal and not statistically significant decreases in the 1996 to 2005 period ( 2.1%), but the AAPC in 2006–2010 was 20.3% (p < 0.05). Of note, the changes could be identified starting in 2007.
1349 U.S. Epilepsy Hospital Stays Increase in 2006
Table 1. Estimates of hospitalizations and age-adjusted rates of stays per 100,000 persons with epilepsy and seizures diagnoses, United States 1993–2010 HCUP- NIS
NHDS Principal discharge diagnosis
Year 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Mean 1996–2005 APC 1996–2005 2006 2007 2008 2009 2010 Mean 2006–2010 AAPC 2006–2010
Epilepsy (345.X) Number 46,387 48,864 48,345 51,902 46,549 51,066 49,327 54,320 57,738 70,567 54,107
Epilepsy (345.XX)
Epilepsy NOS (345.9)
Seizures NOS (780.39)
Epilepsy (345.XX)
Number
Number
Number
Rate
Number
Rate
58,800 58,280 51,757 51,201 56,079 53,544 52,699 60,189 60,246 62,314 56,511
22.3 21.6 18.9 18.6 20.2 19.1 18.4 20.8 20.6 21.1
14,295 11,757 10,689 11,561 14,041 12,031 13,687 14,692 14,140 11,570 12,846
5.4 4.3 3.9 4.2 5.0 4.3 4.8 5.1 4.8 3.9
0.4 73,146 136,300 170,484 178,891 205,892 152,943
Discharges with any mention in discharge diagnoses of
79,336 145,086 187,610 200,110 220,239 166,476
26.6 43.3 61.9 65.4 71.5 24.7a
27,556 32,843 25,992 23,230 25,378 26,657 25,905 25,771 26,799 21,671 26,180
0.4 23,115 74,854 106,100 113,280 132,342 89,938
7.8 24.9 35.0 37.0 43.0
Rate 10.4 12.1 9.5 8.4 9.1 9.5 9.0 8.9 9.2 7.3
113,018 119,144 109,170 98,811 106,723 98,402 109,389 111,419 105,648 116,147 108,787
2.1 21,536 11,752 7,050 10,680 7,503 11,704
45.8a
7.2 3.9 2.3 3.5 2.4 20.3a
Rate 42.8 44.1 40.0 35.9 38.4 35.0 38.1 38.5 36.1 39.3
Epilepsy NOS (345.9)
Seizures NOS (780.39)
Number
Number
Rate
711,546 739,123 735,928 775,297 745,509 785,106 803,274 852,046 903,805 871,043 792,268
269.5 273.3 269.4 281.4 268.0 279.4 279.8 294.3 309.1 295.1
41,132 44,812 38,690 35,469 42,890 35,941 44,646 44,558 38,417 43,665 41,022
1.8 155,251 441,074 618,988 705,160 740,788 532,252
52.1 146.8 204.4 230.6 240.6 38.8a
Rate 15.6 16.6 14.2 12.9 15.4 12.8 15.5 15.4 13.1 14.8
1.1 75,226 330,087 483,876 561,914 591,608 408,542
25.3 109.9 159.8 183.8 192.2 55.4a
0.6 853,425 653,006 412,784 329,274 322,088 514,115
286.4 217.3 136.3 107.7 104.6 25.4a
Note: if there were no changes in trends, then AAPC equals APC. APC, annual percent change; AAPC, average annual percent change. a p < 0.05. Sources: CDC NCHS, NHD: National Hospital Discharge Survey, Public Use files 1996–2010, and HCUP: Healthcare Cost Utilization Project, Nationwide Inpatient Sample, http://hcupnet.ahrq.gov/HCUPnet.jsp.
The number of discharges with any mention of epilepsy (ICD-9-CM 345.XX) in the seven fields coding for discharge diagnoses changed little in the 1996–2005 time period, but increased by almost fivefold in the 2006–2010 period (i.e., 532,252/108,787). The AAPC in 2006–2010 was 38.8% (p < 0.05). The changes observed in the estimated number of discharges with any mention of unspecified epilepsy (ICD-9-CM 345.9) increased by almost 10fold (i.e., 408,542/41,022), and the AAPC in 2006–2010 was 55.4% (p < 0.05). The total number of discharges with any mention of unspecified seizures (ICD-9-CM 780.39) changed little in the 1996–2005 period, but the decrease in 2006–2010 ( 35.1%, i.e., 278,153/792,268) was statistically significant. Table 2 shows the results of the trend analysis of ageadjusted hospital stays per 100,000, using joinpoint regression. For discharges with epilepsy (ICD-9-CM 345.XX), either as principal discharge diagnosis or as epilepsy unspecified (ICD-9-CM 345.9), there were clearly three distinct segments: the period 1996–2005 without changes in
the rates, and a sudden and statistically significant increase in 2006–2008, followed by a plateau without significant change since 2008. In contrast, the time series of rates for hospital stays with seizures not specified (ICD-9-CM 780.39), as principal discharge diagnosis or any mention of unspecified seizures, had only one statistically significant joinpoint, breaking the series into two segments 1996–2005 and 2006–2010. As shown in Figure 1, the changes were sudden and simultaneous in 2006. The increase in principal discharge diagnosis of any type of epilepsy (ICD-9-CM 345.XX) shown in the series at top of the panel A of Figure 1, representing all types of epilepsy, could be attributed to the increase in diagnoses of epilepsy without any other specification regarding type (ICD-9-CM 345.9). At the same time, the rates of hospital stays with principal discharge diagnoses coded as due to seizures not otherwise specified (ICD-9CM 780.39) dropped from around 10 stays per 100,000 to 2 per 100,000. Panel B of Figure 1, shows that the occurrence of hospitalizations with seizures not otherwise specified Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
1350 V. M. C ardenas et al. Table 2. Trends in age-adjusted rates of hospital stays of epilepsy-related diagnoses in the US, 1996–2010 Discharge Diagnosis
Joinpoints
Time period (segments)
Annual percent change
Epilepsy as principal (ICD-9-CM 345.XX)
2
Unspecified epilepsy as principal (ICD-9-CM 345.9)
2
Seizures NOS as principal (ICD-9-CM 780.39)
1
Any mention of epilepsy (ICD-9-CM 345.XX)
2
Any mention of unspecified epilepsy (ICD-9-CM 345.9)
2
Any mention of seizures NOS (ICD-9-CM 780.39)
1
1996–2005 2005–2008 2008–2010 1996–2005 2005–2008 2008–2010 1996–2004 2004–2010 1996–2005 2005–2008 2008–2010 1996–2005 2005–2008 2008–2010 1996–2006 2006–2010
0.4 48.0a 5.1 3.8 105.3a 3.6 2.1 31.0a 1.8 83.4a 5.0 1.1 137.1a 1.9 0.6 25.4a
a
95% CI 2.5, 1.8 17.2, 86.9 16.8, 32.8 3.8, 3.0 41.3, 198.4 28.7, 50.6 8.3, 4.5 28.0, 11.7 3.6, 0.0 50.4, 123.8 13.9, 28.1 4.0, 1.9 71.5, 227.7 26.3, 40.8 1.2, 2.4 30.6, 19.7
p < 0.05.Source: CDC NCHS, NHDS Public Use files 1996–2010.
Figure 2. Age-specific rates of hospitalization with epilepsy as principal discharge diagnosis between 1996–2005 and 2006–2010. Epilepsia ILAE
Figure 1. Estimates of age-adjusted hospitalization rates with discharge diagnoses of epilepsy and seizure disorders in 1996–2010, United States of America. (A) Principal discharge diagnosis. (B) Any discharge diagnosis. Epilepsia ILAE Epilepsia, 55(9):1347–1354, 2014 doi: 10.1111/epi.12719
(ICD-9-CM 780.39) in any of the discharge diagnoses decreased by two thirds from around 300 discharges per 100,000 to 100 per 100,000, whereas the rates of hospital stays with any type of epilepsy (ICD-9-CM 345.XX) in any of the discharge diagnoses increased from
