JOURNAL OF NEUROTRAUMA 30:67–75 (January 15, 2013) ª Mary Ann Liebert, Inc. DOI: 10.1089/neu.2012.2605
Original Articles
Causes and Trends in Traumatic Brain Injury for United States Adolescents Anthony O. Asemota,1,2 Benjamin P. George,1–3 Steven M. Bowman,4 Adil H. Haider,1,2 and Eric B. Schneider1
Abstract
Traumatic brain injury (TBI) is a leading cause of death and disability among United States adolescents. The authors sought to determine causes and trends for TBI-related hospitalizations in the United States adolescent population (10–19 years). The authors identified common causes and trends of adolescent TBI, overall and within 2-year age categories, using hospitalization data from 2005 to 2009 in the Nationwide Inpatient Sample. The leading cause of adolescent TBI overall was motor vehicle occupant accidents (35%), which are also the leading cause in the 14–15, 16–17, and 18–19 year age groups. Falls were the cause of most TBI in the 10–11 year (23%) and 12–13 year (20%) age groups. For both unintentional and intentional mechanisms of injury, there was evidence of increasing hospitalizations with increasing age. From 2005 to 2009, the overall annual incidence of adolescent TBI hospitalizations decreased 21% from an estimated 75.5–59.3 per 100,000 ( p < 0.001). These rates declined for mild, moderate, and severe TBI, and decreased for 2-year age groups, except for the 18–19 year-old group. For TBI attributable to motor vehicle occupants, rates declined 27% from 27.6 to 20.2 per 100,000 ( p < 0.001). Motor vehicle occupant injuries account for 42% of in-hospital mortality from adolescent TBI; however, firearms are the most lethal mechanism with 46% proportional mortality among victims of firearm-related TBI. Rates of adolescent TBI-related hospitalizations have decreased overall. Motor vehicle accidents and firearms were identified as leading causes of injury and mortality for adolescent TBI, and represent potential targets for intervention. Key words: epidemiology; head trauma; pediatric brain injury; TBI
Introduction
Adolescence is a particularly vulnerable period for intentional and unintentional injuries, as it is characterized by risk-taking behavior.8,9 Furthermore, adolescent susceptibility to TBI may be heightened because of exposure to high school sports, assault, and motor vehicle injury.10,11 TBI in children and adolescents is potentially fatal, but may also lead to long-term disability.12 For adolescents, TBI could greatly impair quality of life at an early stage creating significant health consequences and escalating the burden of care for families and caregivers.13 Given the vulnerability of adolescents to TBI and the possible shortand long-term consequences, it is important to understand the trends and patterns of occurrence to increase the effectiveness of injury prevention strategies. To date, most studies have focused on older adults and younger children, largely restricted to 5-year age groups.10,14,15 This study examines common causes and trends in adolescent TBIrelated hospitalizations and deaths in the United States from 2005 to 2009, exploring hospitalization rates in 2-year age categories.
T
raumatic brain injury (TBI) is a significant problem confronting young persons in the United States.1 Each year in the United States, > 1,000,000 new cases of TBI are diagnosed in the general population with *50,000 cases resulting in death.1–3 TBI accounts for one-third of all injury related deaths in the United States with high incidence rates in younger age groups.1,4 The World Health Organization projects that TBI will be among the leading causes of morbidity and mortality by 2020,5 and the economic costs of TBI in the United States is estimated to be $60 billion annually.6 In 2000, there were *50,000 TBI-associated hospitalizations in children and adolescents £ 17 years of age, which corresponds to more than $1 billion in acute care costs.7 Despite the growing importance of TBI, there is little known about the specific causes and trends among adolescent age groups (10–19 years of age).
1
Center for Surgical Trials and Outcomes Research, Department of Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland. Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland. 3 University of Rochester School of Medicine and Dentistry, Rochester, New York. 4 Department of Community Health, National University Technology and Health Sciences Center, San Diego, California. 2
67
68 Methods Data source We analyzed discharge data from the Nationwide Inpatient Sample (NIS) of the Healthcare Cost and Utilization Project.16 The NIS dataset is a cross-sectional, all-payer, inpatient care dataset in the United States, consolidated on an annual basis, containing information on *8,000,000 hospitalizations annually from 1,050 hospitals in 44 states. It is the only national hospital database that includes persons covered by Medicare, Medicaid, and private insurance, as well as uninsured patients, and represents a 20% stratified sample of all non-federated community hospitals. The sampling frame embodied 95% of all United States hospital discharges in 2009. Discharge data provided in the NIS includes patient demographic information as well as information on diagnosis, geographic location, payer status, hospital charges, length of stay, discharge disposition, and in-hospital death. Information on hospital characteristics, such as teaching status and bed size, can be matched to individual hospitalizations. The Johns Hopkins Institutional Review Board approved the study.
ASEMOTA ET AL. such as the abdomen. Information on hospital teaching status, bed size (small, medium, and large), region (Northeast, Midwest, South, and West), and urban/rural location were obtained from the hospital characteristics dataset. Bed size classification varies based on region and urban/rural location.16 Hospitalization rates To generate national estimates of hospitalizations for each year studied, the frequencies obtained from the NIS were scaled using discharge weights provided by the Healthcare Cost and Utilization Project (HCUP). National estimates of hospitalizations obtained by this method are comparable across years, despite the varying numbers of states participating in the dataset each year. As recommended by the HCUP Methods Series for population denominator use with HCUP databases,22 we used the United States Census Bureau American Community Survey from an Integrated Public Use Microdata Series to estimate the national civilian population.23 We used age and year specific adolescent population estimates to calculate TBI hospitalization rates from 2005 to 2009 by mechanism of injury.
Inclusion criteria
Statistical analysis
We used the International Classification of Disease, ninth revision, Clinical Modification (ICD-9-CM) diagnostic codes to identify hospitalized cases 10–19 years of age with a primary or secondary diagnosis of TBI (800.0–801.9, 803.0–804.9, and 850.0– 854.1). The TBI case definition is consistent with Centers for Disease Control and Prevention recommendations.17 The NIS contains no unique patient identifiers; therefore, hospitalizations resulting in patient transfers to another hospital were excluded from the analysis to avoid double counting.18 Because of the nature of the sample, this study excludes adolescents with TBI discharged directly from the emergency department, treated exclusively in outpatient settings, and those who did not report their injury.
Analyses were performed with the appropriate weighted, stratified, sample design, using the survey command options within Stata version 12.0. (Stata, College Station, TX). Demographics, hospital characteristics, and outcomes were reported by year using descriptive statistics. Hospitalization rates were calculated by mechanism of injury within each age subgroup over time. We compared hospitalization rates and outcomes in 2005 versus 2009 using adjusted Wald tests. For categorical variables, comparisons were made using v2 analysis.
Patient characteristics For a more detailed perspective by age, we used reported patient age for each hospitalization subdivided into five 2-year age groups (10–11, 12–13, 14–15, 16–17, and 18–19 years of age). Mechanism of injury was determined using external causes of injury codes (Ecodes). For persons with more than one E-code, the primary code was used. External cause of injury was identified in 89% of all hospitalizations studied from 2005 to 2009. Mechanism of injury was categorized based on injury and intent according to the Centers for Disease Control and Prevention recommended framework for injury mechanisms (http://www.cdc.gov/injury/wisqars/ecode_ matrix.html). The Abbreviated Injury Scale (AIS) score, a valid and widely used measure, was employed to stratify injury severity among adolescent TBI admissions.14,19,20 AIS scores were calculated from ICD-9-CM diagnosis and procedure codes using ICDMAP-90 software.21 The injury severity scores range from 1 to 6 (least to most severe, where 6 represents an unsurvivable injury) and are calculated individually for each of six body regions. For the purposes of this study, brain injuries with a score of 1 or 2 were categorized as mild, those with a score of 3 were categorized as moderate, and those with a score of 4, 5 or 6 were categorized as severe. To examine brain injury among all hospital admissions, all individuals with brain injury of any severity were included for descriptive study. Proportional mortality by injury mechanism was examined in the entire group of patients admitted with head trauma, some of whom may have had injuries to other body regions, which could have contributed to their risk of mortality. A separate analysis of proportional mortality was also performed to examine cases with primary/isolated head trauma in the subset of patients who did not have a moderate-to-severe injury to any non-head body region,
Sensitivity analysis Three states (Maine from 2007–2009, Texas from 2005–2009, and California in some records from 2005–2009) restrict reporting on age by assigning individual hospitalizations to the midpoint of their respective 5-year age groups.16 Therefore, individual records may be incorrectly categorized within our reported 2-year age groups. We found that 18% of the United States adolescent TBI population is found within these three states; therefore, we conducted a sensitivity analysis excluding Maine, Texas, and California populations to determine the overall effect of potential age miscategorization. Results A total of 139,798 adolescent TBI hospitalizations were observed, accounting for *10% of all TBI hospitalizations between 2005 and 2009. Patient and hospital characteristics are presented in Table 1. During the study period, there was an overall incidence of 66.8 TBI-related adolescent hospitalizations per 100,000. Males accounted for 71% of hospitalizations, and individuals ‡ 16 years of age accounted for 63% of cases over the study period. In the subgroup of individuals for whom race data were available, 66% were identified as being of white race, 12% were identified as black, 15% Hispanic, and 7% other (e.g., Native American, Asian, or Pacific Islander). Most patients were treated at teaching hospitals (76%) and hospitals in urban areas (95%). The proportion of TBI-related hospitalizations attributable to external causes of injury by each 2-year age group can be seen in Figure 1. Throughout the study time frame, 35% of adolescent TBI hospitalizations were caused by motor vehicle occupant injuries and 14% by falls, and 12% occurred as a result of being struck, cut, or pierced by an object/person. Motor vehicle occupant accidents
CAUSES AND TRENDS IN US ADOLESCENT TBI
69
Table 1. National Trends in the Incidence of Adolescent TBI-Related Hospitalizations by Demographics, Hospital Characteristics, and Injury Severity, 2005–2009 TBI hospitalizations (% of overall) Patient characteristics Overall Sex Male Female Race White Black Hispanic Other Missing Mean age (SD) Age category 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Injury Severity Mild Moderate Severe Hospital characteristics Teaching status Teaching hospital Bed size Small Medium Large Region Northeast Midwest South West Urban/rural location Urban
2005
2006
2007
2008
2009
Total
p value
30,467 (100)
31,237 (100)
28,610 (100)
24,458 (100)
25,026 (100)
139,798 (100)
21,131 (69) 9,148 (30)
22,040 (71) 9,072 (29)
20,831 (73) 7,703 (27)
17,472 (71) 6,892 (28)
17,573 (70) 7,340 (29)
99,047 (71) 40,155 (29)
13,873 2,067 2,846 1,645 10,036 15.6
(46) (7) (9) (5) (33) (2.7)
15,051 2,602 3,015 1,605 8,965 16.0
(48) (8) (10) (5) (29) (2.5)
12,645 2,510 3,653 1,257 8,544 16.0
(44) (9) (13) (4) (30) (2.5)
12,328 2,294 2,856 1,600 5,380 16.1
(50) (9) (12) (7) (22) (2.5)
14,090 2,532 3,105 1,599 3,702 16.0
(56) (10) (12) (6) (15) (2.5)
67,987 12,004 15,474 7,705 36,628 15.9
(49) (9) (11) (6) (26) (2.6)
< 0.0001
2,694 4,848 5,339 8,654 8,932
(9) (16) (18) (28) (29)
1,959 4,053 5,016 9,556 10,653
(6) (13) (16) (31) (34)
2,003 3,455 4,648 8,720 9,784
(7) (12) (16) (30) (34)
1,511 2,635 3,910 7,599 8,803
(6) (11) (16) (31) (36)
1,669 3,096 4,305 7,368 8,588
(7) (12) (17) (29) (34)
9,836 18,087 23,218 41,897 46,760
(7) (13) (17) (30) (33)
< 0.0001
0.0019
< 0.0001
13,635 (45) 12,126 (40) 4,705 (15)
14,556 (47) 11,436 (37) 5,247 (17)
12,429 (43) 11,096 (39) 5,084 (18)
11,675 (48) 8,955 (37) 3,827 (16)
11,548 (46) 9,509 (38) 3,970 (16)
63,844 (46) 53,122 (38) 22,833 (16)
< 0.0001
21,099 (69)
24,318 (78)
23,104 (81)
18,397 (75)
19,082 (76)
105,697 (76)
< 0.0001
3,150 (10) 7,802 (26) 19,514 (64)
2,061 (7) 6,655 (21) 22,522 (72)
2,146 (8) 4,819 (17) 21,645 (76)
1,056 (4) 4,187 (17) 19,215 (79)
1,576 (6) 5,104 (20) 17,653 (71)
9,960 (7) 28,486 (20) 100,259 (72)
< 0.0001
7,618 6,802 10,861 5,957
4,717 6,362 12,034 5,496
5,534 8,234 9,833 6,865
(18) (27) (32) (23)
29,033 (95)
(24) (22) (35) (19)
29,736 (95)
(16) (22) (42) (19)
27,151 (95)
5,590 4,975 8,420 5,473
(23) (20) (34) (22)
6,307 (25) 4,338(17) 8,281 (33) 6,101 (24)
23,250 (95)
23,377 (93)
(21) (22) (35) (21)
< 0.0001
132,167 (95)
0.0576
29,684 30,620 49,285 29,809
TBI, traumatic brain injury.
FIG. 1. External cause of traumatic brain injury by 2-year age groups, 2005–2009. External cause of injury (mechanism of injury) was identified using primary external cause of injury codes (E-codes) provided in the Nationwide Inpatient Sample.
70
ASEMOTA ET AL. Table 2. National Trends in Incidence of Adolescent TBI-Related Hospitalizations by Mechanism and 2-Year Age Groups, 2005–2009 TBI hospitalization rate per 100,000
Injury mechanism
2005
2006
2007
2008
2009
Total
% Change, 2005–2009
All mechanisms Motor vehicle occupantsa Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Motorcycles Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Bicycles Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Pedestrians Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Other transportb Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Falls Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Firearms Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Struck, cut, or pierced Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years
75.5
73.7
67.7
57.9
59.3
66.8
- 21*
27.6 6.8 9.1 16.4 48.0 63.6
25.8 3.7 7.1 13.6 45.5 56.4
22.5 4.6 6.1 11.8 40.6 46.1
20.2 3.5 4.4 10.0 35.5 44.0
20.2 3.3 5.4 11.1 34.2 43.9
23.2 4.4 6.4 12.6 40.7 50.2
- 27* - 52* - 41* - 32* - 29* - 31*
1.7 0.4 0.9 1.2 1.9 4.6
1.9 0.2 0.5 1.6 2.6 4.8
2.0 0.3 0.6 1.2 2.8 4.6
1.8 0.1 0.8 1.1 2.5 4.3
1.5 0.2 0.7 1.1 1.6 3.8
1.8 0.2 0.7 1.2 2.3 4.4
- 11 - 56 - 19 -6 - 17 - 17
5.7 4.9 10.1 7.2 3.5 2.2
4.6 4.1 6.8 5.5 4.0 2.4
4.5 4.2 6.9 5.7 3.8 2.3
3.8 3.2 4.5 5.4 3.4 2.6
4.4 3.6 5.9 5.7 3.8 3.0
4.6 4.0 6.8 5.9 3.7 2.5
- 23* - 27 - 42* - 21 9 36*
4.0 3.1 4.6 4.1 3.8 4.2
4.3 2.2 4.7 5.0 5.4 4.2
3.5 2.2 3.5 3.6 3.8 4.3
3.6 2.3 3.9 4.5 3.8 3.4
3.6 2.2 3.8 3.6 4.2 4.0
3.8 2.4 4.1 4.2 4.2 4.0
-9 - 29 - 16 - 11 11 -5
6.3 3.1 7.5 7.5 7.5 5.7
5.9 2.9 5.4 7.3 7.9 6.0
5.6 2.3 5.7 6.0 7.4 6.2
5.2 2.1 4.3 5.4 8.0 6.1
5.1 1.8 5.0 6.9 6.7 4.9
5.6 2.4 5.6 6.7 7.5 5.8
- 20* - 42* - 34* -8 - 11 - 14
9.7 7.0 9.8 9.6 11.1 11.2
9.7 5.8 10.2 8.5 11.6 12.4
8.5 5.1 7.2 8.8 10.5 10.7
8.6 3.9 7.5 7.9 11.8 11.3
9.9 5.9 8.8 9.7 12.8 12.0
9.3 5.5 8.7 8.9 11.6 11.5
2 - 16 - 10 2 15 8*
NA NA 0.5 1.1 2.5 3.1
1.6 0.2 0.6 1.4 1.9 3.6
NA NA 0.4 0.9 2.9 3.7
NA NA 0.2 0.6 1.7 2.9
NA NA 0.5 0.6 1.9 2.6
NA NA 0.4 0.9 2.2 3.2
NA NA 18 - 50 - 23 - 15
8.8 3.3 8.2 7.6 12.8 12.5
8.1 2.5 6.2 7.1 13.1 11.4
7.6 2.5 4.9 7.8 11.3 10.7
8.0 2.4 4.0 8.2 12.6 12.2
8.2 2.8 4.6 9.1 12.8 11.3
8.1 2.7 5.6 7.9 12.5 11.6
-7 - 17 - 44* 19 - 0.3 -9 (continued)
CAUSES AND TRENDS IN US ADOLESCENT TBI
71
Table 2. (Continued) TBI hospitalization rate per 100,000 Injury mechanism Other injury Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years Missing injury codesc Overall 10–11 years 12–13 years 14–15 years 16–17 years 18–19 years
2005
2006
2007
2008
2009
Total
% Change, 2005–2009
2.9 0.8 1.4 2.5 3.7 6.4
3.1 0.4 2.0 2.6 5.4 5.1
3.8 0.8 2.3 3.7 4.9 7.0
2.7 0.7 1.0 1.8 4.5 5.1
2.5 0.5 1.0 2.0 4.1 4.8
3.0 0.6 1.5 2.5 4.5 5.7
- 11 - 33* - 29* - 22* 11* - 25*
7.6 3.9 5.6 5.2 9.8 14.2
8.6 2.3 5.3 5.6 13.6 15.4
8.1 3.0 4.4 5.4 12.1 14.7
2.7 0.8 1.5 2.1 4.1 4.7
2.8 0.4 2.1 1.9 4.8 4.5
5.9 2.1 3.8 4.1 8.9 10.5
- 63* - 89* - 63* - 63* - 51* - 68*
*Statistically significant, p < 0.05. b Motor vehicle occupants category includes unspecified motor vehicle injuries. c Other transport includes off-road vehicles, all-terrain vehicles, and others. d Missing injury codes account for *11% of the total population from 2005 to 2009. NA, not available because of suppression of observations £ 10 in compliance with the Agency for Healthcare Research and Quality confidentiality guidelines for Healthcare Cost and Utilization Project data series. TBI, traumatic brain injury.
FIG. 2. Traumatic brain injury (TBI)-related hospitalization rates in 2-year age groups for (A) unintentional and (B) intentional mechanisms of injury, 2005–2009. Intentional injury includes mechanisms classified as self-harm and assault by the Centers for Disease Control and Prevention.
72
ASEMOTA ET AL.
are the leading cause of injury in older age groups accounting for 23% in those ages 14–15 years, 42% in those ages 16–17 years, and 46% in those ages18–19 years. Falls are the greatest external cause of TBI in younger age categories (10–11, 12–13 years), accounting for > 20% of cases for each subgroup. Motor vehicle occupant accidents (16%) and bicycle-related accidents (16%) are also leading causes of TBI in these younger age groups. Overall, incidence rates for TBI hospitalizations decreased 21% from an estimated 75.5 to 59.3 per 100,000 from 2005 to 2009 ( p < 0.001). Hospitalization rates of mild TBI decreased 19% from 33.8 to 27.4 per 100,000 ( p < 0.001). Rates of moderate TBI declined 25% from 30.1 to 22.5 per 100,000 over the 5-year study period, and severe TBI declined 11% from 11.7 to 9.4 per 100,000. TBI hospitalization rates decreased over time for most 2-year age groups. The decrease in the rate of TBI hospitalizations from 2005 to 2009 differed among the various age groups, with a > 35%
decline among adolescents 10–11and 12–13 years of age, and a > 14% decline for those 14–15 and 16–17 years of age. Rates for adolescents 18–19 years of age decreased by 4%, although this change was not significant ( p = 0.243). TBI-related hospitalization rates by mechanism of injury for 2year age groups over time can be seen in Table 2. For the majority of injury mechanisms, TBI hospitalizations either decreased or did not change significantly over the 5-year period. For example, TBI hospitalization rates in adolescents attributable to motor vehicle occupant injuries declined 27% from 27.6 to 20.2 per 100,000 from 2005 to 2009. However, both bicycle and fall-related TBI hospitalizations increased for the 18–19 year age group by 75% ( p = 0.012) and 40% ( p = 0.001), respectively.TBI hospitalizations caused by falls increased 18% for the 16–17 year age group, although this trend was not significant ( p = 0.063). Of the total adolescent TBI-related hospitalizations caused by falls, 28% were categorized as sports related by external cause of injury codes. A
Table 3. Outcomes for Adolescent TBI-Related Hospitalizations Stratified by Injury Severity, 2005–2009 TBI hospitalizations (% of overall) Outcomes Mild injury Overall Disposition Routine discharge Other transfers Home health care Othera Fatality Non-fatal Fatal Median length of stayb Median total charges (USD)b Moderate injury Overall Disposition Routine discharge Other transfers Home health care Other** Fatality Non-fatal Fatal Median length of stayb Median total charges (USD)b Severe injury Overall Disposition Routine discharge Other transfers Home health care Othera Fatality Non-fatal Fatal Median Length of Stayb Median Total Charges (USD)b
2005
2009
Total, 2005–2009
% Change, 2005–2009
13,635 (100)
11,548 (100)
63,844 (100)
- 15*
12,608 (92) 465 (3) 374 (3) 85 (1)
10,649 (92) 513 (4) 279 (2) 57 (0)
58,837 (92) 2,541 (4) 1,697 (3) 427 (1)
- 16* 10 - 25 - 33
13,532 (99.2) 25 (0.2) 2 14118.00
11,489 (99.5) 16 (0.1) 2 21858.00
63,493 (99.5) 114 (0.2) 2 17398.50
- 15* - 36 0 55*
12,126 (100)
9,509 (100)
53,122 (100)
- 5*
9,356 (77) 1,715 (14) 295 (2) 88 (1)
7,254 (76) 1,549 (16) 232 (2) 69 (1)
40,915 (77) 7,651 (14) 1,486 (3) 377 (1)
- 22* - 10 - 21 - 22
11,444 (94) 597 (5) 3 24530.00
9,089 (96) 345 (4) 3 34765.00
50,384 (95) 2,417 (5) 3 28931.00
- 21* - 42* 0 42*
4,705 (100)
3,970 (100)
22,833 (100)
- 16*
3,088 (66) 742 (16) 102 (2) 50 (1)
2,586 (65) 783 (20) 73 (2) 15 (0)
14,679 (64) 3,952 (17) 668 (3) 147 (1)
- 16* 6 - 28 - 70*
3,982 (85) 688 (15) 3 29313.00
3,452 (87) 493 (12) 3 40793.00
16,557 (73) 2,764 (12) 3 35385.50
- 13* - 28* 0 39*
S * tatistically significant, p < 0.05. a Other discharge includes against medical advice, unknown, or missing. b Median length of stay and total charges are based upon unweighted data and total charges represent unadjusted hospital charges from each year. For example, 2005 charges are reported in 2005 US dollars and 2009 charges are reported in 2009 US dollars. TBI, traumatic brain injury; USD, United States Dollars
CAUSES AND TRENDS IN US ADOLESCENT TBI
73
similar proportion of struck, cut, or piercing injuries were also sports related (25%). There was an increase in incidence of TBI-related hospitalizations with increasing age for both unintentional and intentional (i.e., assault and self-harm) mechanisms of injury. Comparing the youngest (10–11 years of age) with the oldest adolescent age group (18–19 years of age), there was a 4-fold increase in rates of unintentional injury (Fig. 2A) and a 40-fold increase for intentional injury (Fig. 2B). After excluding TBI hospitalizations within states that restrict reporting of age to the midpoint of 5-year age groups, TBI-related hospitalization rates across 2-year age groups from 2005 to 2009 did not change significantly. Forty-six percent of all TBI hospitalizations were categorized as mild, 38% as moderate, and 16% as severe. Of those with mild and moderate brain injury, 23% had a moderate or severe injury to another body region. Table 3 displays outcomes (e.g., discharge disposition, death) for adolescent TBI hospitalizations. The proportion of hospitalizations with moderate TBI that resulted in fatality decreased from 5% in 2005 to 4% in 2009 ( p = 0.037). In addition, the total number of fatalities for moderate and severe TBI significantly declined during the study period. Overall, 4% of TBI-related hospitalizations in adolescents were fatal. The leading cause of fatalities in the entire group admitted with brain injury was motor vehicle occupant injury, accounting for 42% of in-hospital mortality (Fig. 3a). Whereas firearms were linked to 2% of adolescent TBI hospitalizations, firearm injuries were associated with 21% of in-hospital TBI mortality in the entire study group. However, firearm injury accounted for 39% of inhospital deaths in the subset of patients admitted with primary/ isolated head trauma (i.e., no moderate or severe injury to any nonhead body region) (Fig. 3b). Again, excluding individuals with moderate-to-severe injury to body regions other than the head (e.g., the abdomen), 46% of adolescent TBI hospitalizations caused by firearms resulted in fatality (Fig. 4). Discussion TBI continues to be a major public health issue among United States adolescents, with 67 adolescents per 100,000 having experienced a TBI-related hospitalization between 2005 and 2009. To the knowledge of the authors, few studies have focused in detail on the incidence and trends of hospitalizations in the adolescent population caused by TBI.3,14 Our analysis differs from prior studies in its focus on the adolescent population and the examination of population-based rates within 2-year age categories. Our findings suggest an overall temporal trend toward lower incidence in hospitalizations for adolescent TBI. Over the 5 years studied, the annual incidence of adolescent TBI hospitalizations decreased by *20%. These trends are consistent with that observed in previous studies, and may suggest the continued success of injury prevention.3,14 The leading mechanism of TBI in adolescents was motor vehicle occupant injury. Consistent with TBI surveillance studies,1 we found that these accidents were particularly troublesome in the older age groups, causing more than one-third of injuries for adolescents 16–19 years of age. Whereas motor vehicle accidents are the predominant cause of TBI in the entire adolescent population, there appears to be a reduction in TBI hospitalization rates because of motor vehicle occupant injuries over time. This may, in part, be because of a decrease in the number of vehicle miles driven during the time period of the study (0.3% decrease).24 Whereas the exact cause of the trend is uncertain, decline in motor vehicle occupant
FIG. 3. In-hospital fatalities for adolescent traumatic brain injury (TBI)-related hospitalizations by mechanism of injury, 2005– 2009. (A) Not excluding (n = 5,825) and (B) excluding (n = 2,697) individuals with moderate-to-severe injury to body regions other than head (e.g., abdomen). injury appears to be one of the major drivers behind the overall decrease in incidence of adolescent TBI hospitalizations across time observed in this study. Falls and striking, cutting, or piercing injuries were another leading cause of TBI, linked to 10–25% of hospitalizations depending upon the injury and adolescent age group. Our data suggest that fall-related injuries are increasing in 18–19 year olds, and that a substantial proportion of these injuries are associated with sports. However, our data are limited to injuries resulting in inpatient admissions, and, therefore, may not be representative of all sportsrelated brain injuries, many of which are mild and may not require admission to inpatient care. Further study in trends for sportsrelated TBI hospitalizations may be warranted.25
74
ASEMOTA ET AL.
FIG. 4. Crude mortality for adolescent traumatic brain injury (TBI) hospitalizations by mechanism of injury (n = 2,697), excluding individuals with moderate-to-severe injury to body regions other than the head (e.g., abdomen). Proportion of TBI hospitalizations resulting in fatalities was calculated as percent fatal within each mechanism of injury group, and therefore, values do not sum to 100% across mechanisms.
Motor vehicle occupant injury accounts for one third of adolescent TBI hospitalizations and *40% of in-hospital mortality; however, firearm injuries make up only 2% of hospitalizations, but account for *20% of in-hospital mortality. TBIs linked to firearms are also exceptionally lethal in adolescents; nearly half of those admitted after sustaining an injury die within the hospital. Although this likelihood of fatality is unadjusted for other factors such as severity of injury, the degree of physiologic injury, and patient signs and symptoms (e.g., blood pressure), the magnitude of the difference between fatality rates for firearm injuries and those for other mechanisms is compelling. In addition, other studies have found gunshots to be a major predictor of mortality in pediatric trauma patients following adjustment for other patient risk factors.26 Given that TBIs caused byfirearms have not changed substantially over time, they represent a potentially high impact target for intervention and prevention strategies. Limitations A major limitation of the study is the inability to correctly classify adolescents within 3 out of the 44 states represented in the sample to the appropriate 2-year age categories. Given that these states restrict the reporting of age to the midpoint of each 5-year age group, this may overestimate rates for individuals in the 12–13 and 16–17 year age categories and underestimate rates within other categories. However, sensitivity analysis showed that the results are not significantly impacted by the exclusion of individuals from these states. We were also limited in the scope of the analysis, in that our study was confined to hospitalizations for injuries resulting in inpatient admission. Historically, acute care inpatient hospitals have been the most common place of death for TBI patients.1
Despite these limitations, our data provide a reasonable estimate of trends in the incidence of adolescent TBI hospitalizations from a national sample with rates calculated using age- and year-specific total population estimates. The study was not designed to examine predictors of mortality, and is primarily a descriptive analysis of adolescents with a primary or secondary diagnosis of brain injury; however, mechanism-related differences in proportional mortality warrant further exploration, as opportunities may exist for highyield mortality-prevention interventions. Conclusion The number of adolescents hospitalized for TBI has decreased by > 20% from 2005 to 2009. Motor vehicle crashes represent the leading cause of brain injury among adolescents, and are responsible for most of the deaths among all adolescents admitted with TBI. However, injuries resulting from firearms are proportionally the most lethal. Greater understanding of risk factors and causes of TBI and related deaths in adolescents may help in developing effective prevention strategies to promote further injury decline in this vulnerable group. Acknowledgments Dr. Asemota had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Drs. Asemota, George, and Schneider were responsible for the study concept and design. Dr. Schneider was responsible for the acquisition of data. Drs. Asemota, George, and Schneider were responsible for the analysis and interpretation of data. Drs. Asemota and George were responsible for the drafting of
CAUSES AND TRENDS IN US ADOLESCENT TBI the manuscript. Drs. Asemota, George, Bowman, Haider, and Schneider were responsible for the critical revision of the manuscript for important intellectual content. Statistical expertise was provided by Drs. Asemota, George, and Schneider. Administrative, technical, or material support was provided by Drs. Asemota, George, Bowman, Haider, and Schneider. Study supervision was provided by Drs. Bowman, Haider, and Schneider.
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Address correspondence to: Anthony O. Asemota, MBBS, MPH Johns Hopkins University School of Medicine, Department of Surgery Center for Surgical Trials and Outcomes Research 600 N. Wolfe Street, Blalock 618 Baltimore, MD 21287 E-mail:
[email protected]
