ORIGINAL SCIENTIFIC ARTICLES

Mortality Risk after Head InjuryIncreases at 30 YearsColin Harris, BA, Stephen DiRusso, MD, PhD, FACS, Tom Sullivan, BS, Deborah L Benzil, MD

BACKGROUND: Age has long been recognized as a critical factor in predicting outcomes after head injury, withindividuals older than 60 years predicted to have a worse outcome than those younger than 60.The object of this study was to determine the effect of age by decade of life beginning at birthin patients with head injuries of all levels of severity.

STUDY DESIGN: The New York State Trauma Registry was searched for head injuries from January 1, 1994 toDecember 31, 1995; the 13,908 cases found were placed into age groups by decade. Data weresought for each patient on demographics, Glasgow Coma Score, ICD-9 injury code, NewInjury Severity Score (NISS), and mechanism of injury. These data were analyzed with chi-square and one-way ANOVA tests, with significance set at p � 0.05.

RESULTS: The risk of dying was significantly increased in patients beginning at 30 years of age comparedwith those in the younger age groups, with the greatest increases occurring after age 60(p � 0.001). For the population with available Glasgow Coma Score data (n � 12,844), themortality rate for patients ages 0 to 30 was 10.9%, and for patients ages 31 to 50 was 12.4%.The mean Glasgow Coma Score for nonsurvivors ages 0 to 20 (3.9) and for nonsurvivors ages31 to 50 (5.1) were significantly different, with a risk ratio of 1.3 (p � 0.001).

CONCLUSIONS: The risk of dying for patients suffering head injuries increases as early as 30 years of age, makingit necessary for health-care providers to consider increased monitoring and treatment for pa-tients in this younger age group. ( J Am Coll Surg 2003;197:711–716. © 2003 by the AmericanCollege of Surgeons)

Traumatic brain injury (TBI) is a significant publichealth issue in the United States. More than half of thedeaths and most of the disability stemming from traumaare related to head injury.1,2 Basic guidelines have beenestablished for treating TBI3 to help improve survivaland function in this large group of patients. Optimalimplementation of these guidelines is dependent on afull understanding of the many factors that can influ-ence outcomes.

Factors known to impact TBI prognosis include Glas-gow Coma Score (GCS), a standardized grading of neu-rologic function after head injury that includes a motor,verbal, and eye assessment score;4 associated injuries, of-ten measured by the New Injury Severity Score (NISS),

a global scale with points assigned according to severityand number of systems injured;5,6 treatment;7,8 andage.9-14 The independent effect of age on outcomes afterTBI has been documented but is not fully explained byprevious research. This lack is from the nature of theinformation needed to perform a comprehensive studyof head injuries, specifically, a large database collectedprospectively and uniformly over a short time interval tominimize the impact of changes in diagnostics and treat-ment over time.

It has been well documented that the risk of adverseoutcomes increases with age and that this effect is inde-pendent of other variables.9,11 Previous studies have fo-cused on documenting differences between the youngestand oldest patients, but they have not compared theeffect of age on patients across all age groups.9,11,12 Inaddition, previous studies of age as a prognosticator haveincluded patients with only mild or severe injuries, buthave not compared outcomes across these groups.14 Inthis study, we have used the large New York StateTrauma Registry (NYSTR) to assess the total effect ofage on the risk of dying after TBI.

No competing interests declared.

Presented in part in poster format at the Annual Meeting of the AmericanAssociation of Neurological Surgeons, Chicago, IL, April 2002.

Received March 15, 2003; Revised June 10, 2003; Accepted June 10, 2003.From the Departments of Neurosurgery (Harris, Benzil) and Surgery (Di-Russo, Sullivan), New York Medical College, Valhalla and New York, NY.Correspondence address: Deborah L Benzil, MD, Department of Neurosur-gery, New York Medical College, Munger Pavilion, Valhalla, NY 10595.

711© 2003 by the American College of Surgeons ISSN 1072-7515/03/$21.00Published by Elsevier Inc. doi:10.1016/S1072-7515(03)00729-4

METHODSPatient populationPatient information was extracted from the NYSTR, acomprehensive database established by the New YorkState Department of Health in 1992. Seven regions,each with a New York State designated Level I traumacenter, were established, with New York City treatedseparately. Data are included from all seven trauma cen-ters and community hospitals in each of these regions.15

Data collection methods, definitions, and statistical va-lidity have been described previously.16-18

All patients entered in the NYSTR between January1, 1994, and December 31, 1995 (excluding thosetreated in the New York City region because data in thatregion are collected using a different method), were in-cluded in the database for this study. Of the 45,982patients seen in this 2-year period (the most recent2-year period with complete data available to us),13,908 were identified as having head injuries by usingthe International Classification of Diseases (ICD-9) di-agnosis codes. Postresuscitation GCS data, the pivotalanalysis point, were available for 12,844 patients (92%).The demographics of this slightly smaller group did notdiffer significantly from those of the total TBI group(data not shown).

Patients were separated into age groups by decade andwere grouped by GCS, outcomes (survivors versus non-survivors), NISS (n � 12,844), and mechanism of in-jury based on ICD-9 E-codes (n � 13,506). Patients ofall ages were included in the study; the age group 0 to 10included children younger than 1 year.

The recently developed Relative Head Injury SeverityScale (RHISS)19 was also used. The RHISS classifiespatients into one of four groups according to head injuryseverity (none, mild, moderate, and severe) on the basisof anatomic injuries reported by ICD-9 code.

Statistical analysisGCS and mortality by age group were compared in twodifferent ways. GCS was treated both as a continuous

variable and as a discrete variable in separate statisticalanalyses using standard GCS ranges of 3 to 5, 6 to 8, 9 to12, and 13 to 15.

In addition, age groups were compared with eachother in terms of overall mortality rates and NISS. Fre-quencies of mechanism of injury were determined foreach age group. Injury mechanisms were determinedthrough ICD-9 E-codes and then grouped into majorcategories to facilitate comparison between age groups.The null hypothesis of no association with age was testedwith the one-way ANOVA test for continuous data.Groups were assessed for differences with the chi-squaretest, with a small p value indicating a positive associationwith age. Significance was set at p � 0.05 for all analysesunless otherwise stated.

RESULTSPatient demographics and overall mortality rateOf the 12,844 patients identified with head injuries andhaving available GCS, 8,985 (70%) were males and3,859 (30%) were females. As shown in Table 1, theoverall mortality rate for all age groups was 14.7%(range, 5.6% to 30.2%). The mortality rate generallyincreased with age, particularly after age 71 (Fig. 1). Themortality rate for ages 0 to 30 was 10.9%, for ages 31 to50 was 12.4%, and for all patients older than 50 was21.3%. The lowest mortality rate was in the 0-to-10 agegroup (5.6%).

Glasgow Coma Score and outcomesThe GCS of nonsurvivors (n � 1,885) was analyzed as acontinuous variable (Fig. 2). The mean GCS of nonsur-vivors increased significantly first in the 31-to-40 agegroup and in each age group after the 61-to-70 group.

Abbreviations and Acronyms

GCS � Glasgow Coma ScoreNISS � New Injury Severity ScoreNYSTR� New York State Trauma RegistryRHISS � Relative Head Injury Severity ScaleTBI � Traumatic brain injury

Table 1. Mortality Rates by Age Group (n � 12,844)

Age, y nMortalityRate (%)

Mean GlasgowComa Score

0–10 1,276 5.6 3.911–20 2,016 11.9 4.021–30 2,127 13.2 4.231–40 1,883 10.9 4.941–50 1,362 14.4 5.451–60 899 14.5 5.861–70 1,001 16.2 7.271–80 1,147 24.2 8.281–90 921 27.9 9.3

�90 212 30.2 10.6Total 12,844 14.7

712 Harris et al Effect of Age on Outcomes after Head Injury J Am Coll Surg

The mean GCS for nonsurvivors aged 0 to 20 (3.9) andthat for nonsurvivors aged 31 to 50 (5.1) were also sig-nificantly different (p � 0.001).

The distribution of nonsurvivors among standardGCS groups was analyzed for differences between pa-tient age groups. Statistically significant distribution dif-ferences were found first in the 31-to-40 age group andthen in the 41-to-50 age group. After this age group, theGCS distributions did not vary significantly until the71-to-80 age group was reached, with the final signifi-cant difference occurring in the 81-to-90 age group. Themost significant difference was between the 61-to-70and the 71-to-80 age groups. (Figs. 3 and 4).

Mechanism of injuryThe five most common mechanisms of injury were an-alyzed separately; all other mechanisms of injury wereanalyzed together. In this study population, falls werethe most common cause of injury, followed by motorvehicle accidents (32% versus 25%). Falls predominatedas the mechanism of injury in the 0-to-10 age group andall age groups older than 41. Motor vehicle accidentsfollowed by assaults predominated in the other agegroups (ages 11 to 40) (Fig. 5).

New Injury Severity ScoreThe overall New Injury Severity Score (NISS)5 remainedrelatively constant across the age groups (data not

Figure 2. Mean Glasgow Coma Score (GCS) (� SD) of nonsurvivingpatients with head injury analyzed as a continuous variable(n � 1,885). The first significant rise in mean GCS occurs in the31-to-40 age group. The mean GCS then rises significantly again ineach decade after age 60.

Figure 3. Glasgow Coma Score (GCS) groups for nonsurvivors. Bythe 31-to-40 age group, death from head injury occurred in patientswith higher GCS group distributions. This correlation became evenmore pronounced after age 71.

Figure 1. Overall mortality rates for patients identified with trau-matic brain injury and having Glasgow Coma Scores (n � 12,844).The rate climbs relatively steadily with increasing age, albeit withsome degree of a plateau in the middle decades. The increase in themortality rate from the 31-to-40 age group to the 41-to-50 age groupis statistically significant (*).

Figure 4. Mortality by age groups for Glasgow Coma Score (GCS)groups 6 to 8 and 9 to 12. The extreme GCS groups of 3 to 5 and13 to 15 were not plotted.

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shown). But the NISS of nonsurvivors correlated in-versely with age (Fig. 6), indicating that the differencesin survival are not related to associated injuries. TheNISS of nonsurvivors was highest in the 11-to-20 agegroup, followed by the 0-to-10 age group. After age 20the NISS decreased steadily with increasing age. Themean NISS for the 0-to-10 age group (36.9 � 1.8 SEM)and that for the 61-to-70 age group (30.7 � 1.3 SEM)were significantly different, indicating that younger pa-tients suffered more severe initial injuries than theirolder counterparts.

Relative Head Injury Severity ScaleThe newly developed RHISS based on anatomic criteriaof ICD-9 codes closely predicted the effect of age onoutcomes for patients with RHISS of 3 (severe headinjury) (Fig. 7). In fact, the RHISS 3 curve more closelyreflects the age-specific mortality curve than any otherindex or scale. But even in the RHISS 1 and 2 groups(mild and moderate head injury), significant differenceswere seen in mortality after age 61.

DISCUSSIONTraumatic brain injury is a major public health issue inthe United States. Understanding the epidemiology andoutcomes associated with it is essential for institutingappropriate measures for prevention, predicting re-sources and needs with changing population demo-graphics, assessing treatments, and analyzing qualityimprovement.

The adverse effect of increasing age on the risk ofdeath from head injury is most pronounced in patientsmore than 65 years of age; that effect is shown mostclearly in mild or moderately injured patients becausethe most severely injured patients do poorly regardless ofage.20,21 But most studies have focused only on severehead injuries or compared outcomes between patientsyounger than 65 years and those older than 65 years.The progressive increase in adverse outcomes rates be-ginning at 35 years has been demonstrated only in pa-tients with severe head injury.9

Figure 6. Mean New Injury Severity Score (NISS) (� SD) of nonsur-viving patients with head injuries. The mean NISS decreased afterage 20, indicating that older patients actually died with less severesystemic injuries.

Figure 7. Relative Head Injury Severity Scale (RHISS) by age groups.RHISS closely predicts age-specific mortality risk in the RHISS 3group and shows significant age-related increased mortality riskeven with RHISS 1 and 2 (mild and moderate head injury) after age61.

Figure 5. Mechanism of injury by age group. Falls were the mostcommon cause of head injury in the 0-to-10 age group and in allages greater than 41. Motor vehicle accidents (MVAs) accounted forthe highest number of injuries in teens and young adults. Overall,falls accounted for more head injuries than motor vehicle accidents.

714 Harris et al Effect of Age on Outcomes after Head Injury J Am Coll Surg

Our study indicates that the impact of age beginsmuch earlier than previously described.9,20,21 Analysis ofthe mean GCS on admission for patients who did notsurvive demonstrates that the increasing impact of ageon trauma deaths begins in the third decade of life, withpatients in the 31-to-40 age group doing significantlyworse than patients in the 21-to-30 age group (Figs. 2and 3). Our study also reinforces the previously docu-mented increase in the effect of age on traumatic headinjury deaths in the older age groups (in our study, thisdifference was most significant between the 61-to-70and 71-to-80 age groups) (Fig. 1 and Table 1).

The significantly higher GCS of nonsurvivors in the31-to-40 age group shows that these patients presentedwith better prognosis as measured by GCS but had ahigher mortality rate than those patients in the youngerage groups. There is also a much greater likelihood ofdying from mild to moderate head injuries beginning atage 31, and this likelihood accelerates at age 71. In ad-dition, the nearly constant NISS across all age groupsindicates that the difference in mortality rates betweenage groups in our study is independent of the severity ofextracranial injuries (Fig. 5). These results agree with thefindings of others that mortality is dependent on theseverity of intracranial pathology, not on multiple sys-tem trauma as expressed by NISS.1,2

Parallel reports on the impact of age on survival aftermajor trauma have led to changes in the way geriatrictrauma patients are assessed and managed and in themanner in which their families are counseled.22-30 Thesestudies also show increases in ICU lengths of stay, overalllengths of stay, and costs for geriatric trauma patients.Although most studies focus on the impact of age greaterthan 65, at least one study showed a sharp rise in mor-tality between ages 45 and 55 and an increased death ratefrom complications.28 Early invasive monitoring is nowadvocated for older patients after blunt trauma.31 Inthese patients, the sustained effect of significantly re-duced 5-year survival has been identified, well beyondthe immediate postinjury period.29 Our findings specificto patients with TBI suggest similar implications forquality improvement issues and head injury treatmentprotocols. Patients who present with head injuries intheir 30s with relatively high GCS scores (�9) may be athigher risk for serious or fatal complications than wasonce thought. Clinicians must be aware that patients inyounger age groups are already showing the adverse ef-

fects of age on the brain’s ability to repair itself aftertraumatic head injury.

Author ContributionsStudy conception and design: Benzil, DiRussoAcquisition of data: Harris, SullivanAnalysis and interpretation of data: Harris, Sullivan,

BenzilDrafting of manuscript: Harris, BenzilCritical revision: BenzilStatistical expertise: Sullivan, DiRussoSupervision: Benzil, DiRusso

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