Vol. 19, No. 1 Printed in Great Britain
International Journal of Epidemiology ©International Epidemiological Association 1990
The Epidemiology of Head Trauma in Aquitaine (France), 1986: A Community-Based Study of Hospital Admissions and Deaths LAURENCE TIRET*. ELIZABETH HAUSHERR**, MICHEL THICOIPEt, BERTRAND GARROS*. PIERRE MAURETTEt, JEAN-PIERRE CASTEL5 AND FRANCOISE HATTON**
In the past decade, several epidemiological studies on head trauma have been reported,1" showing the magnitude of this major public health problem both in terms of mortality and morbidity. However, all these studies were conducted in Anglo-Saxon countries, whereas Latin countries may have different patterns of incidence and causes owing to different environmental or behavioural factors. Moreover, previous studies generally focused on the problem of head trauma alone, whereas most head-injured patients have
multiple injuries, all of them likely to influence the outcome.12 During 1986, a population-based study was conducted in France, including all injuries serious enough either to result in death prior to hospitalization or to require hospitalization.13 Results reported here concern the incidence and causes of head trauma, the associated injuries and the overall injury severity of head-injured patients measured by the Injury Severity Score (ISS), and lastly the outcome within eight days.
* Institut National de la Santfi et de la Recherche Medicale (INSERM), Unite1 258, Hopital Broussais, 96 rue Didot, 75674 Paris Ce'dex 14, France. "Institut National de la Santl et de la Recherche Medicale (INSERM), UnitiS 164, 16 Avenue Paul Vaillant-Couturier, 94807 Villejuif Ce'dex, France. tD^partement d'Anesth£sie-R£animation, Centre Hospitalier Regional, 33076 Bordeaux, France. iObservatoire Regional de la Santl d'Aquitaine, 58 Rue de Marseille, 33000 Bordeaux, France. §Service de Neurochirurgie, Centre Hospitalier Regional, 33076 Bordeaux, France.
METHODS The study was carried out prospectively during a oneyear period (1986) in a defined geographical region of France, the Aquitaine (2.7 million people, 4.9% of the whole population of France), containing both urban and rural areas. Data Collection Injuries included in the current study were those likely to produce a head trauma, namely physical injuries 133
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Tiret L (Institut National de la Sante et de la Recherche Medicale (INSERM), Unite 258, Hopital Broussais, 96 rue Didot, 75674 Paris Cedex 14, France), Hausherr E, Thicoipe M, Garros B, Maurette P, Castel J P and Hatton F. The epidemiology of head trauma in Aquitaine (France), 1986: A community-based study of hospital admissions and deaths. International Journal of Epidemiology 1990, 19: 133-140. This paper reports the findings of a study of head trauma conducted over a one-year period within a defined region with a population of 2.7 million (Aquitaine, France). It includes cases resulting in death prior to hospitalization or requiring hospitalization. During the one-year period, 391 deaths and 8549 hospital admissions due to head trauma occu rred, yielding an annual estimate of 8940 head-inju red people. The immediate case-fatality rate was 4.4%. Among non-fatal cases, 80% were mild, 11 % moderate and 9% severe. The overall annual incidence was 281/100 000 in both sexes (384 and 185/100 000 in males and females respectively). The annual death rate was 22/100 000 (33 and 12, respectively). Patterns of incidence by age and sex were in general agreement with earlier studies. The main causes of head trauma were traffic accidents (60%) and falls (33%). One-third of hospitalized patients had no injury other than the head trauma. The most frequently associated injuries were those involving extremities, whereas the most severe were those involving the abdomen. The Injury Severity Score (ISS) ranged from 4 to 66, with a mean of 9 and a median of 5. At the eighth day following injury, 25% of hospital-treated patients were still hospitalized and 2% had died. The outcome correlated well with the ISS.
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
Data Collected For each inpatient, the medical staff of the institution completed a questionnaire within 24 hours of admission. Outcome within eight days was added later. The clinical nature of injuries was coded according to a classification into 180 codes specially devised for this study. The purpose of this classification was to provide an automatic computation of the Abbreviated Injury Scale (AIS)14 and the Injury Severity Score (ISS),15 which is the most widely used score for rating severity of multiple injuries.* According to the 1980-AIS manual, head injuries are described in terms of anatomical lesions as well as level of consciousness. 'For the computation of the ISS, six areas of the body are defined. An AIS score ranging from one (minor) to six (fatal) is attributed to each injury within the different body areas. The ISS is then the sum of the squares of the highest AIS scores in each of the three most severely injured body areas.
For the purposes of the current study, head trauma was defined as contusions, lacerations, skull fractures or brain injuries, and/or loss of consciousness after a relevant injury. Facial injuries without loss of consciousness were not included in this definition. Head trauma resulting in hospitalization was classified into three groups according to severity: (1) severe, including brain injuries or coma greater than six hours; (2) moderate, including skull fractures without diagnosed brain injury, or loss of consciousness greater than 15 minutes up to six hours; (3) mild, including contusions without loss of consciousness or with a loss of consciousness not exceeding 15 minutes. Analysis In the event of transfer, only the first hospital admission for the episode was considered. Data concerning hospital admissions were extrapolated from the sample to an annual basis. The coefficient of extrapolation, which adjusted for the missing cases in hospitals which had not participated, was 4.04. Data concerning immediate deaths were added to provide an estimate of the annual number of cases. Incidences were assessed among residents of Aquitaine. The 1986 reference population was estimated from the 1982 census. Tables concerning associated injuries and the ISS were derived only from the admission sample, since this information was not available for cases dead prior to hospitalization. Mortality Statistics In order to compare our figures to those of previous studies, annual death rates from head trauma were calculated. These rates were derived from the 1986 routine mortality statistics for Aquitaine. They included all deaths from head trauma and were not limited to immediate deaths. RESULTS Fifty-nine of the 64 hospitals selected participated in the study, performing 98% of the total traumatological activity of the region. During the one-year period, 891 immediate deaths from injury were registered and 7281 hospital admissions were observed during the sampling periods, yielding an annual estimate of 30 310 injured people (Table 1). Among all injured patients, 30% sustained a head trauma. This proportion was higher among fatal cases (44%) than among admitted cases (29%). The immediate case-fatality rate was higher in patients with head trauma (1/23) than in the whole injured population (1/34). According to our classification of severity, 9% of non-fatal head trauma was severe, 11% moderate and 80% mild.
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caused by an external (mechanical) force, either resulting in death before reaching hospital or requiring hospital admission. Injuries to residents and non-residents of the region were both recorded. Data collection was performed using the two following sources: 1. Injured cases requiring hospital admission were studied on a representative sample basis. All public and private hospitals regularly involved in the treatment of injuries, because of their geographical position or the presence of a trauma specialist, were included in the study. Among other private hospitals, one out of two was randomly selected. In each institution, the survey lasted 13 weeks spread over the whole year. • the teaching hospital was investigated every fourth week; • non-teaching and private hospitals of thefirstcategory were divided into four groups, each being investigated during three periods (four weeks, four weeks and five weeks). The survey was initiated successively in each group with an interval of four weeks, the whole year therefore being covered by the study; • private hospitals of the second category were divided into two groups, each being successively investigated during a 13-week period. This scheme provided a sample representative by time of the day, day of the week and season. The presence of a referral teaching hospital in the region reduced the possibility of treatment outside the region. 2. Injured cases resulting in death prior to hospitalization were recorded from death certificates on an exhaustive annual basis. All cases registered in the region during the one-year period were included, except for those that were registered in a public or private hospital.
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EPIDEMIOLOGY OF HEAD TRAUMA TABLE 1 Proportion of patients with head trauma among all injured patients Proportion of All injured Patients with patients with head trauma head trauma patients Immediate deaths* Hospital admissions'* Estimated annual number of injured peoplet Immediate deaths/total injured
891 7281
391 2116
43.9% 29.1%
30310
8940
29.5%
1/34
1/23
* During a one-year period ** During the 13-week sample periods. t (Sampled admissions X4.04) + immediate deaths.
External Cause Traffic accidents were the most frequent cause of head trauma. They produced 60% of all cases and nearly 70% of fatal cases. Falls were the second leading cause, resulting more often in moderate or mild cases. Firearms injuries caused 13% of fatal cases, but were involved in less than 0.5% of non-fatal cases (Table 2). Age- and sex-specific incidence rates of head trauma from traffic accidents and falls are shown in Figures 3 and 4. Patterns of incidence were quite different according to the cause. For traffic accidents, the highest risk concerned the 15-24 year age group, whereas for falls, groups at risk were at both extremes of life. For both causes, male rates exceeded female ones at almost all ages, except underfiveyears of age for traffic accidents, and over 75 years for falls. Associated Injuries One-third of hospitalized patients had no injury other
Rate per 100 000 800
T
700 - -
600 • -
Males
Age
-f0
10
20
30
40
50
60
70
80
FIGURE 1 Annual incidence of head trauma per 100000 population (immediate deaths + admissions); by age and sex, Aquitaine, France. 1986.
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Incidence The overall annual incidence of head trauma was 281 per 100 000 population. It was higher in males (384 per 100 000) than in females (185 per 100 000), the sex ratio of incidence being 2.1. In both sexes, three peaks of incidence occurred (Figure 1). The first one at under five years of age, the second in the 15-24 years age group (substantially more marked in males), and the last one at over 75 years. At any age, male rates were higher than female ones. The sex ratio of incidence increased with age to reach a maximum in the 25-34 year age group (3.2) and then declined gradually.
Mortality The annual death rate from head trauma was 22 per 100 000 population. It was nearly three times higher in males than in females (33 versus 12 per 100000). The peak of incidence in the 15-24 year age group was still marked, but the highest rates were observed in the elderly (Figure 2). The proportion of immediate deaths occurring before admission was 54.8%.
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY Rate per 100 000 100 -r
0
10
Males
20
30
40
SO
60
70
80
than the head trauma. This proportion was higher among moderate head traumas (45%). Except for external injuries, the most frequently associated injuries were those involving extremities, whatever the severity of head trauma. Injuries of the face were also often observed, whereas injuries of the neck, the chest or the abdomen were less frequent, being mostly associated with severe head trauma. According to the AIS mean, abdominal injuries were the most severe (Table 3). Injury Severity Score (ISS) Among all patients hospitalized with head trauma, the ISS ranged from 4 to 66 with a mean of 9. The minimum score of 4 corresponded to mild head trauma or simple skull fractures without associated injury. As expected, the ISS mean increased dramatically with the severity of head trauma. In the severe group, the median was 25 and the third quartile 34, indicating that most patients in this group had sustained severe multiple injuries. The different quartiles were much lower in the moderate and mild groups. Nevertheless, some high values of ISS were also observed in these groups, since head trauma could be associated with severe injuries involving other body areas (Table 4). TABLE 2
The overall severity varied with the external cause of injury, traffic and firearms' accidents leading to the highest ISS values (Table 4). Outcomes of Patients Admitted to Hospital At the eighth day following accident, 73% of patients had been discharged, 20% were still hospitalized, 5% had been transferred and 2% had died (Table 5). The length of hospitalization increased with the severity of head trauma. Whereas hospital mortality within eight days was very low in both the mild and moderate groups, it was higher than 20% in the severe group. Rate per 100 000 600 -r
Distribution of head trauma by external cause of injury
Traffic accidents Falls Struck by object Firearms Others
All head trauma (%)
Fatal
Severe
Moderate
%
%
%
59.6 32.5 6.1 0.9
68.7 14.1
0.9
1.6
64.3 26.8 5.8 2.6 0.5
51.3 44.2 3.3 0.4 0.8
59.7 32.5 6.8 0.1 0.9
100.0
100.O
100.0
100.0
100.0
2.1
13.5
Mild %
Age
FIGURE 3 Annual incidence of head trauma from traffic accidents per 100 000 population (immediate deaths + admissions), by age and sex, Aquitaine, France, 1986.
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FIGURE 2 Annual death rale from head trauma per 100 000 population (all deaths), by age and sex, Aquitaine, France, 1986.
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EPIDEMIOLOGY OF HEAD TRAUMA Rate per 100 000 350 -r
FIGURE 4 Annual incidence of head trauma from falls per 100000 population (immediate deaths + admissions), by age and sex, Aquilaine, France, 1986.
The outcome within eight days correlated well with the ISS, mortality and length of hospitalization both increasing with the score (Table 5). DISCUSSION Methodological Aspects All previous epidemiological reports on head trauma TABLE 3
Associated AIS body areas injured in hospitalized patients with head trauma
AIS body area Face Neck Chest Abdomen Extremities External No associated injury
All head trauma %* AIS mean**
Severe Moderate
AIS mean % AIS mean
12.9 1.4 6.2 2.3 9.1 2.0
°/
5.6
AIS mean % AIS mean % AIS mean
3.0 25.5 2.1 42.3 1.1
17.9 1.4 15.3 2.2 14.7 3.0 12.1 3.5 35.2 2.6 37.9 1.2
%
33.8
31.1
0/
14.5 1.6 5.8 2.1 7.8
Mild
20.7 2.3 32.6 1.2
12.2 1.4 5.3 2.4 8.6 1.8 5.0 2.8 25.1 2.0 44.2 1.1
45.0
32.5
2.2 4.1
2.8
* Per cent is calculated successively among all, severe, moderate and mild head trauma. It represents the percentage of patients with an injury of the area in the given category of head trauma. * * AIS mean is calculated among patients having at least one injury in the AIS body area concerned.
TABLE 4 Injury Severity Score (ISS) of hospitalized patients with head trauma, according to the severity of head trauma and to the external cause of injury ISS
Range
Mean
Ql
Median
Q3
Severity of head trauma severe 9-66 moderate 4^»1 mild 4-50
26.8 10.6 6.8
17 4 4
25 9 5
34 16 8
External cause of injury traffic accident falls struck by object firearms others
4-66 4-36 4-^tl 5-25 4-42
10.4 6.9 6.5 18.1 8.2
5 4 4 9 4
6 5 5 22 5
13 8 6 25 7
All head trauma
4-66
9.0
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Age
have emphasized the lack of a common clear definition of head trauma. Some studies included all head trauma,5'8'" others excluded bruises and gunshot wounds.9 Some were restricted to presumed brain injuries, excluding10 or not2 skull fractures. We defined head trauma in the broadest sense, including one or more of the following criteria: blow to the head, loss of consciousness, skull fracture or brain injury. As with most studies, our survey was based on cases severe enough either to result in death before hospitalization or to require hospital admission. As already stated,8'6 criterion of admission is questionable, since it depends on the hospital policy and the access to health care. Moreover, studying a specific injuiry by screening hospitalized patients may introduce a bias, since in the case of multiple injuries, the hospitalization may be due to other injuries than the injury of interest. However, Fife12 showed that when the injury of interest was the head injury, this problem was relatively mild because the head injury accounted for most of the overall injury severity. Similarly in our survey, head trauma accounted for 75% of the overall injury severity measured by the ISS (unpublished data). The possible sources of bias in this survey have already been discussed in a previous report concerning all injuries.13 The main bias consists of a likely underestimation of deaths before admission, since in the case of 'suspect' cause of death, some certificates are sent directly to the legal authorities. This problem, presumably concerning suicides and homicides, minimizes the weight of firearm injuries in the current study, but it is less likely to affect traffic accidents and falls, which are the main causes of head trauma.25-8-I° Some hospitalized cases may also have been missed because of failure to identify brain injury. This could occur either because lesions appeared with delay and were not reported in the questionnaire, or because of a
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY TABLE 5
Outcome at the eighth day following accident of hospitalized patients, according to the severity of head trauma and to ISS Discharged
Still hospitalized
Transferred
Died
Total
Severity of head trauma severe moderate mild
17.7 55.2 81.7
46.5 30.7 15.1
13.9 13.7 2.9
21.9 0.4 0.3
100.0 100.0 100.0
ISS Class 4-9 10-19 5*20
87.3 40.5 10.7
9.4 49.4 53.3
3.1 8.9 15.7
0.2 1.2 20.3
100.0 100.0 100.0
All head trauma
72.9
19.7
5.2
2.2
100.0
The Findings This is thefirstpopulation-based study of head trauma in France. As already stated the comparison of our results with those of studies carried out in other countries is difficult, since many differences exist in
definition and case ascertainment, time and place of study and analysis. We selected three studies which seemed comparable to ours in definition and case ascertainment and were confined to a defined geographical area (San Diego County9 and Olmsted County2 in the United States) or to a whole country (Great Britain).8 As shown in Table 6, the 1986 incidence rate in Aquitaine of 281/100 000 is similar to that reported in San Diego, intermediate between those of England and Scotland (not including deaths) and higher than that of Olmsted County. Klauber9 explained the higher rates in San Diego than in Olmsted County by a more complete case ascertainment in the prospective California study, compared to the retrospective study of Olmsted County. As our study was also prospective, it could explain the higher rates in Aquitaine. Actually, the mortality rates from head trauma, which are less likely to be affected by the problem of ascertainment, are similar between the three studies (Table 6). Mortality rates in Great Britain are substantially lower, but the proportion of deaths attributable to accidents is lower in Great Britain than in most other countries.8 This is partly related to the lower incidence of deaths from traffic accidents.19 The proportion of mild head trauma (80% of hospitalized cases) was similar to that reported in Scotland" and higher than that in Olmsted County (65%).2 A likely explanation is tnat fewer patients with mild injuries are admitted to hospitals in the United States than in France and Great Britain.8 Although these trauma generally require only a few days of hospitalization, the workload involved in their care is important given their large number. Patterns of incidence by age and sex, and male to female incidence ratio are in general agreement with findings from earlier studies.2-5'8"10 While the greatest peak of incidence is always reported between 15 and 24 years of age, due to traffic accidents, children and the elderly also appear to be at higher risk because of falls
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lack of appropriate diagnostic facilities in some hospitals. Another point deserving mention is the classification of head traumas into three groups of increasing severity: mild, moderate and severe. Several studies have adopted such a classification, but there is lack of uniformity in the definition of groups. Whitman" and Annegers2 used a classification combining the level of consciousness and the type of lesions. We adopted a similar classification, but with different bounds of level of consciousness. In particular, our class of severe, including comas longer than six hours, is larger than in Whitman's" and Annegers's2 studies (both included comas longer than 24 hours). The limit of six hours was adopted here to relate to the Glasgow Coma Scale (GCS), which is assessed over the sixth hour. Kraus10 and Miller" applied the GCS but not with the same bounds of classes. The GCS18 is now widely used to assess the severity of head injury. Although there are a number of limitations in its application,10 this grading system undoubtedly constitutes a useful tool for clinical and epidemiological purposes. However, our study focused initially on all injuries, and for that reason, we adopted the AIS, which is a general classification of injury severity, at the expense of scales concerning more specific problems. However, comparing our classification of severity with the GCS, we can say that our class of mild head trauma roughly corresponds to the 'mild' GCS class (score = 13 or more), whereas our class of severe is broader than the 'severe' GCS class (score = 8 or less), since it also includes brain injuries not necessarily associated with a coma at the sixth hour.
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EPIDEMIOLOGY OF HEAD TRAUMA TABLE 6
Incidence rales of head trauma from four selected studies
Population
Field of study
Sex
Aquilaine France 1986
Hospital admissions and immediate deaths
Both Male Female
281 384 184
22.3* 33.4* 11.9*
San Diego USA 1978
Hospital admissions and all deaths
Both Male Female
295
22.3 31.8 12.1
Great Britain 1974
Hospital admissions
Both Both
270 (England) 313 (Scotland)
Olmsted County USA 1935-74
Hospital admissions and all deaths
Male Female
274 116
Incidence rate/100000
Death rate/100000
9.2* 9.3* 35.0 10.0
experienced at these ages. The rate in 15-24 year agegroup males is similar in Aquitaine (750/100 000) to that reported in San Diego.9 In actual fact, mortality from traffic accidents is nearly the same in both countries." As in previous studies, mortality from head trauma increased with age.2'8'10 In our study, 4.4% of head trauma was immediately fatal. This proportion is similar to that in San Diego (4.8%).9 The case-fatality rate of patients admitted to hospital in Aquitaine was 2.2% within eight days. We assessed, on the basis of routine mortality statistics,20 that the total case-fatality rate (not limited to eight days) of hospitalized patients would be about 3.8%. This value is intermediate between those reported in other studies5910 which ranged from 3% to 6%. This implies that about 60% of hospital deaths would occur within eight days of admission. Uniquely this report describes the epidemiology of head trauma-associated injuries and the assessment of overall severity of head-injured patients, using the ISS. This global approach to the head-injured patient is relevant, since most of them sustain multiple injuries, as shown in Table 3. The treatment of injuries other than head trauma add considerably to the workload of services involved in their care, and they contribute to prolonging the hospital stay of many cases with mild head trauma. As expected, the ISS was predictive of the outcome within eight days. In the group of patients having an ISS above 20, in-hospital mortality was very high (20%). With regard to the length of hospitalization, there was a frontier between scores under and above ten. In the former group, only 10% of patients were still hospitalized at the eighth day, whereas this proportion was 50% in the latter group. In conclusion, this study shows that the problem of head trauma is of similar magnitude in France and in
Anglo-Saxon countries, despite likely differences in environmental and cultural factors, prevention policies and organization of health care systems. Further improvements must be accomplished in the prevention of head trauma, especially in the 15-24 year age group. Besides severe head trauma, which often leads to death or serious impairment, the great number of mild head trauma, which may have neurological and behavioural sequellae1016 constitute a major matter of concern for public health. ACKNOWLEDGEMENTS This study was supported by the 'Direction Regionale des Affaires Sanitaires et Sociales d'Aquitaine', the 'Conseil Regional d'Aquitaine', the 'Caisse Regionale d'Assurance Maladie d'Aquitaine', the 'Ministere de l'Equipement, du Logement, de PAmenagement du Territoire et des Transports (Securite Routiere)' and the 'Ministere de l'lnterieur (Securite Civile)'. The authors gratefully acknowledge the cooperation given by the institutions who participated in the study. They also wish to thank E Michel and V Lambert for computer programming, C Cretaz for collecting death certificates and B Mrabet and D Rebeyrol for supervising the data collection in institutions. REFERENCES ' Anderson D W. Miller J D. Kalsbeek W D. Findings from a major US survey of persons hospitalized with head injuries. Pub Hlth Rep 1983; 98: 475-8. 2 Annegers J F, Grabow J D, Kurland L T, Laws E R. The incidence, causes and secular trends of head trauma in Olmsted County, Minnesota, 1935-1974. Neurology 1980; 30: 912-9. ' Cooper K D, Tabaddor K, Hauser W A, Shulman K, Feiner C, Factor P R. The epidemiology of head injury in the Bronx. Neuroepidemiol 1983; 2: 70-88. ' Edna T H, Cappelen J. Hospital admitted head injury. A prospective study in Trondelag, Norway, 1979-80. ScandJSoc Med 1984; 12: 7-14.
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•Rates drawn from mortality statistics, including all deaths.
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Tiret L, Garros B, Maurette P, etal. Incidence, causes and severity of injuries in Aquitaine (France). A community-based study of hospital admissions and deaths. Am J Publ Health 1989; 79: 316-21. 14 Committee on Injury Scaling: The Abbreviated Injury Scale (AIS), 1980 revision. American Association for Automotive Medicine, Morton Grove, IL, 1980. 15 Baker S P, O'Neill B, Haddon W, Long W B. The Injury Severity Score: A method for describing patients with multiple injuries and evaluating emergency care. J Trauma 1974; 14: 187-96. 16 Fife D. Head injury with and without hospital admission: Comparisons of incidence and short-term disability. Am J Pub Hlth 1987; 77: 810-2. "Miller J D, Jones P A. The workload of a regional head injury service. Lancet 1985; 1: 1141^1. '8Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet 1974; 2: 81—4. "World Health Organization. World Health Statistics Annual. Geneve: 1987. 20 Statistiques des causes medicales de deces, Aquitaine, 1986. INSERM (unpublished data).
(Revised version received June 1989)
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Fife D, Faich G, Hollinshead W, Boyton W. Incidence and outcome of hospital-treated head injury in Rhode Island. Am J Pub Hlth 1986; 76: 773-8. * Frankowski R F. Descriptive epidemiologic studies of head injury in the United States: 1974-1984. Adv Psychosom Med 1986; 16: 153-72. 7 Galbraith S, Murray W R, Patel A R. Head injury admissions to a teaching hospital. Scot MedJ 1977; 22: 129-32. 8 Jennett B, Mac Millan R. Epidemiology of head injury. Br Med J 1981; 282: lOl^J. ' Klauber M R, Barret-Connor E, Marshall L F, Bowers S A. The epidemiology of head injury. A prospective study of an entire community—San Diego County, California 1978. Am J Epidemiol 1981; 113:500-9. 10 Kraus J F, Black M A, Hessol N, et al. The incidence of acute brain injury and serious impairment in a defined population. Am J Epidemiol 1984; 119: 186-201. " Whitman S, Coonley-Hoganson R, Desai B T. Comparative head trauma experiences in two socioeconomicalfy different Chicago-area communities: A population study. Am J Epidemiol 1984; 119: 570-80. 12 Fife D, Jagger J. The contribution of brain injury to the overall injury severity of brain-injured patients. J Neurosurg 1984; 60: 697-9.
International Journal of Epidemiology ©International Epidemiological Association 1990
The Epidemiology of Head Trauma in Aquitaine (France), 1986: A Community-Based Study of Hospital Admissions and Deaths LAURENCE TIRET*. ELIZABETH HAUSHERR**, MICHEL THICOIPEt, BERTRAND GARROS*. PIERRE MAURETTEt, JEAN-PIERRE CASTEL5 AND FRANCOISE HATTON**
In the past decade, several epidemiological studies on head trauma have been reported,1" showing the magnitude of this major public health problem both in terms of mortality and morbidity. However, all these studies were conducted in Anglo-Saxon countries, whereas Latin countries may have different patterns of incidence and causes owing to different environmental or behavioural factors. Moreover, previous studies generally focused on the problem of head trauma alone, whereas most head-injured patients have
multiple injuries, all of them likely to influence the outcome.12 During 1986, a population-based study was conducted in France, including all injuries serious enough either to result in death prior to hospitalization or to require hospitalization.13 Results reported here concern the incidence and causes of head trauma, the associated injuries and the overall injury severity of head-injured patients measured by the Injury Severity Score (ISS), and lastly the outcome within eight days.
* Institut National de la Santfi et de la Recherche Medicale (INSERM), Unite1 258, Hopital Broussais, 96 rue Didot, 75674 Paris Ce'dex 14, France. "Institut National de la Santl et de la Recherche Medicale (INSERM), UnitiS 164, 16 Avenue Paul Vaillant-Couturier, 94807 Villejuif Ce'dex, France. tD^partement d'Anesth£sie-R£animation, Centre Hospitalier Regional, 33076 Bordeaux, France. iObservatoire Regional de la Santl d'Aquitaine, 58 Rue de Marseille, 33000 Bordeaux, France. §Service de Neurochirurgie, Centre Hospitalier Regional, 33076 Bordeaux, France.
METHODS The study was carried out prospectively during a oneyear period (1986) in a defined geographical region of France, the Aquitaine (2.7 million people, 4.9% of the whole population of France), containing both urban and rural areas. Data Collection Injuries included in the current study were those likely to produce a head trauma, namely physical injuries 133
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Tiret L (Institut National de la Sante et de la Recherche Medicale (INSERM), Unite 258, Hopital Broussais, 96 rue Didot, 75674 Paris Cedex 14, France), Hausherr E, Thicoipe M, Garros B, Maurette P, Castel J P and Hatton F. The epidemiology of head trauma in Aquitaine (France), 1986: A community-based study of hospital admissions and deaths. International Journal of Epidemiology 1990, 19: 133-140. This paper reports the findings of a study of head trauma conducted over a one-year period within a defined region with a population of 2.7 million (Aquitaine, France). It includes cases resulting in death prior to hospitalization or requiring hospitalization. During the one-year period, 391 deaths and 8549 hospital admissions due to head trauma occu rred, yielding an annual estimate of 8940 head-inju red people. The immediate case-fatality rate was 4.4%. Among non-fatal cases, 80% were mild, 11 % moderate and 9% severe. The overall annual incidence was 281/100 000 in both sexes (384 and 185/100 000 in males and females respectively). The annual death rate was 22/100 000 (33 and 12, respectively). Patterns of incidence by age and sex were in general agreement with earlier studies. The main causes of head trauma were traffic accidents (60%) and falls (33%). One-third of hospitalized patients had no injury other than the head trauma. The most frequently associated injuries were those involving extremities, whereas the most severe were those involving the abdomen. The Injury Severity Score (ISS) ranged from 4 to 66, with a mean of 9 and a median of 5. At the eighth day following injury, 25% of hospital-treated patients were still hospitalized and 2% had died. The outcome correlated well with the ISS.
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
Data Collected For each inpatient, the medical staff of the institution completed a questionnaire within 24 hours of admission. Outcome within eight days was added later. The clinical nature of injuries was coded according to a classification into 180 codes specially devised for this study. The purpose of this classification was to provide an automatic computation of the Abbreviated Injury Scale (AIS)14 and the Injury Severity Score (ISS),15 which is the most widely used score for rating severity of multiple injuries.* According to the 1980-AIS manual, head injuries are described in terms of anatomical lesions as well as level of consciousness. 'For the computation of the ISS, six areas of the body are defined. An AIS score ranging from one (minor) to six (fatal) is attributed to each injury within the different body areas. The ISS is then the sum of the squares of the highest AIS scores in each of the three most severely injured body areas.
For the purposes of the current study, head trauma was defined as contusions, lacerations, skull fractures or brain injuries, and/or loss of consciousness after a relevant injury. Facial injuries without loss of consciousness were not included in this definition. Head trauma resulting in hospitalization was classified into three groups according to severity: (1) severe, including brain injuries or coma greater than six hours; (2) moderate, including skull fractures without diagnosed brain injury, or loss of consciousness greater than 15 minutes up to six hours; (3) mild, including contusions without loss of consciousness or with a loss of consciousness not exceeding 15 minutes. Analysis In the event of transfer, only the first hospital admission for the episode was considered. Data concerning hospital admissions were extrapolated from the sample to an annual basis. The coefficient of extrapolation, which adjusted for the missing cases in hospitals which had not participated, was 4.04. Data concerning immediate deaths were added to provide an estimate of the annual number of cases. Incidences were assessed among residents of Aquitaine. The 1986 reference population was estimated from the 1982 census. Tables concerning associated injuries and the ISS were derived only from the admission sample, since this information was not available for cases dead prior to hospitalization. Mortality Statistics In order to compare our figures to those of previous studies, annual death rates from head trauma were calculated. These rates were derived from the 1986 routine mortality statistics for Aquitaine. They included all deaths from head trauma and were not limited to immediate deaths. RESULTS Fifty-nine of the 64 hospitals selected participated in the study, performing 98% of the total traumatological activity of the region. During the one-year period, 891 immediate deaths from injury were registered and 7281 hospital admissions were observed during the sampling periods, yielding an annual estimate of 30 310 injured people (Table 1). Among all injured patients, 30% sustained a head trauma. This proportion was higher among fatal cases (44%) than among admitted cases (29%). The immediate case-fatality rate was higher in patients with head trauma (1/23) than in the whole injured population (1/34). According to our classification of severity, 9% of non-fatal head trauma was severe, 11% moderate and 80% mild.
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caused by an external (mechanical) force, either resulting in death before reaching hospital or requiring hospital admission. Injuries to residents and non-residents of the region were both recorded. Data collection was performed using the two following sources: 1. Injured cases requiring hospital admission were studied on a representative sample basis. All public and private hospitals regularly involved in the treatment of injuries, because of their geographical position or the presence of a trauma specialist, were included in the study. Among other private hospitals, one out of two was randomly selected. In each institution, the survey lasted 13 weeks spread over the whole year. • the teaching hospital was investigated every fourth week; • non-teaching and private hospitals of thefirstcategory were divided into four groups, each being investigated during three periods (four weeks, four weeks and five weeks). The survey was initiated successively in each group with an interval of four weeks, the whole year therefore being covered by the study; • private hospitals of the second category were divided into two groups, each being successively investigated during a 13-week period. This scheme provided a sample representative by time of the day, day of the week and season. The presence of a referral teaching hospital in the region reduced the possibility of treatment outside the region. 2. Injured cases resulting in death prior to hospitalization were recorded from death certificates on an exhaustive annual basis. All cases registered in the region during the one-year period were included, except for those that were registered in a public or private hospital.
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EPIDEMIOLOGY OF HEAD TRAUMA TABLE 1 Proportion of patients with head trauma among all injured patients Proportion of All injured Patients with patients with head trauma head trauma patients Immediate deaths* Hospital admissions'* Estimated annual number of injured peoplet Immediate deaths/total injured
891 7281
391 2116
43.9% 29.1%
30310
8940
29.5%
1/34
1/23
* During a one-year period ** During the 13-week sample periods. t (Sampled admissions X4.04) + immediate deaths.
External Cause Traffic accidents were the most frequent cause of head trauma. They produced 60% of all cases and nearly 70% of fatal cases. Falls were the second leading cause, resulting more often in moderate or mild cases. Firearms injuries caused 13% of fatal cases, but were involved in less than 0.5% of non-fatal cases (Table 2). Age- and sex-specific incidence rates of head trauma from traffic accidents and falls are shown in Figures 3 and 4. Patterns of incidence were quite different according to the cause. For traffic accidents, the highest risk concerned the 15-24 year age group, whereas for falls, groups at risk were at both extremes of life. For both causes, male rates exceeded female ones at almost all ages, except underfiveyears of age for traffic accidents, and over 75 years for falls. Associated Injuries One-third of hospitalized patients had no injury other
Rate per 100 000 800
T
700 - -
600 • -
Males
Age
-f0
10
20
30
40
50
60
70
80
FIGURE 1 Annual incidence of head trauma per 100000 population (immediate deaths + admissions); by age and sex, Aquitaine, France. 1986.
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Incidence The overall annual incidence of head trauma was 281 per 100 000 population. It was higher in males (384 per 100 000) than in females (185 per 100 000), the sex ratio of incidence being 2.1. In both sexes, three peaks of incidence occurred (Figure 1). The first one at under five years of age, the second in the 15-24 years age group (substantially more marked in males), and the last one at over 75 years. At any age, male rates were higher than female ones. The sex ratio of incidence increased with age to reach a maximum in the 25-34 year age group (3.2) and then declined gradually.
Mortality The annual death rate from head trauma was 22 per 100 000 population. It was nearly three times higher in males than in females (33 versus 12 per 100000). The peak of incidence in the 15-24 year age group was still marked, but the highest rates were observed in the elderly (Figure 2). The proportion of immediate deaths occurring before admission was 54.8%.
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY Rate per 100 000 100 -r
0
10
Males
20
30
40
SO
60
70
80
than the head trauma. This proportion was higher among moderate head traumas (45%). Except for external injuries, the most frequently associated injuries were those involving extremities, whatever the severity of head trauma. Injuries of the face were also often observed, whereas injuries of the neck, the chest or the abdomen were less frequent, being mostly associated with severe head trauma. According to the AIS mean, abdominal injuries were the most severe (Table 3). Injury Severity Score (ISS) Among all patients hospitalized with head trauma, the ISS ranged from 4 to 66 with a mean of 9. The minimum score of 4 corresponded to mild head trauma or simple skull fractures without associated injury. As expected, the ISS mean increased dramatically with the severity of head trauma. In the severe group, the median was 25 and the third quartile 34, indicating that most patients in this group had sustained severe multiple injuries. The different quartiles were much lower in the moderate and mild groups. Nevertheless, some high values of ISS were also observed in these groups, since head trauma could be associated with severe injuries involving other body areas (Table 4). TABLE 2
The overall severity varied with the external cause of injury, traffic and firearms' accidents leading to the highest ISS values (Table 4). Outcomes of Patients Admitted to Hospital At the eighth day following accident, 73% of patients had been discharged, 20% were still hospitalized, 5% had been transferred and 2% had died (Table 5). The length of hospitalization increased with the severity of head trauma. Whereas hospital mortality within eight days was very low in both the mild and moderate groups, it was higher than 20% in the severe group. Rate per 100 000 600 -r
Distribution of head trauma by external cause of injury
Traffic accidents Falls Struck by object Firearms Others
All head trauma (%)
Fatal
Severe
Moderate
%
%
%
59.6 32.5 6.1 0.9
68.7 14.1
0.9
1.6
64.3 26.8 5.8 2.6 0.5
51.3 44.2 3.3 0.4 0.8
59.7 32.5 6.8 0.1 0.9
100.0
100.O
100.0
100.0
100.0
2.1
13.5
Mild %
Age
FIGURE 3 Annual incidence of head trauma from traffic accidents per 100 000 population (immediate deaths + admissions), by age and sex, Aquitaine, France, 1986.
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FIGURE 2 Annual death rale from head trauma per 100 000 population (all deaths), by age and sex, Aquitaine, France, 1986.
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EPIDEMIOLOGY OF HEAD TRAUMA Rate per 100 000 350 -r
FIGURE 4 Annual incidence of head trauma from falls per 100000 population (immediate deaths + admissions), by age and sex, Aquilaine, France, 1986.
The outcome within eight days correlated well with the ISS, mortality and length of hospitalization both increasing with the score (Table 5). DISCUSSION Methodological Aspects All previous epidemiological reports on head trauma TABLE 3
Associated AIS body areas injured in hospitalized patients with head trauma
AIS body area Face Neck Chest Abdomen Extremities External No associated injury
All head trauma %* AIS mean**
Severe Moderate
AIS mean % AIS mean
12.9 1.4 6.2 2.3 9.1 2.0
°/
5.6
AIS mean % AIS mean % AIS mean
3.0 25.5 2.1 42.3 1.1
17.9 1.4 15.3 2.2 14.7 3.0 12.1 3.5 35.2 2.6 37.9 1.2
%
33.8
31.1
0/
14.5 1.6 5.8 2.1 7.8
Mild
20.7 2.3 32.6 1.2
12.2 1.4 5.3 2.4 8.6 1.8 5.0 2.8 25.1 2.0 44.2 1.1
45.0
32.5
2.2 4.1
2.8
* Per cent is calculated successively among all, severe, moderate and mild head trauma. It represents the percentage of patients with an injury of the area in the given category of head trauma. * * AIS mean is calculated among patients having at least one injury in the AIS body area concerned.
TABLE 4 Injury Severity Score (ISS) of hospitalized patients with head trauma, according to the severity of head trauma and to the external cause of injury ISS
Range
Mean
Ql
Median
Q3
Severity of head trauma severe 9-66 moderate 4^»1 mild 4-50
26.8 10.6 6.8
17 4 4
25 9 5
34 16 8
External cause of injury traffic accident falls struck by object firearms others
4-66 4-36 4-^tl 5-25 4-42
10.4 6.9 6.5 18.1 8.2
5 4 4 9 4
6 5 5 22 5
13 8 6 25 7
All head trauma
4-66
9.0
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Age
have emphasized the lack of a common clear definition of head trauma. Some studies included all head trauma,5'8'" others excluded bruises and gunshot wounds.9 Some were restricted to presumed brain injuries, excluding10 or not2 skull fractures. We defined head trauma in the broadest sense, including one or more of the following criteria: blow to the head, loss of consciousness, skull fracture or brain injury. As with most studies, our survey was based on cases severe enough either to result in death before hospitalization or to require hospital admission. As already stated,8'6 criterion of admission is questionable, since it depends on the hospital policy and the access to health care. Moreover, studying a specific injuiry by screening hospitalized patients may introduce a bias, since in the case of multiple injuries, the hospitalization may be due to other injuries than the injury of interest. However, Fife12 showed that when the injury of interest was the head injury, this problem was relatively mild because the head injury accounted for most of the overall injury severity. Similarly in our survey, head trauma accounted for 75% of the overall injury severity measured by the ISS (unpublished data). The possible sources of bias in this survey have already been discussed in a previous report concerning all injuries.13 The main bias consists of a likely underestimation of deaths before admission, since in the case of 'suspect' cause of death, some certificates are sent directly to the legal authorities. This problem, presumably concerning suicides and homicides, minimizes the weight of firearm injuries in the current study, but it is less likely to affect traffic accidents and falls, which are the main causes of head trauma.25-8-I° Some hospitalized cases may also have been missed because of failure to identify brain injury. This could occur either because lesions appeared with delay and were not reported in the questionnaire, or because of a
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INTERNATIONAL JOURNAL OF EPIDEMIOLOGY TABLE 5
Outcome at the eighth day following accident of hospitalized patients, according to the severity of head trauma and to ISS Discharged
Still hospitalized
Transferred
Died
Total
Severity of head trauma severe moderate mild
17.7 55.2 81.7
46.5 30.7 15.1
13.9 13.7 2.9
21.9 0.4 0.3
100.0 100.0 100.0
ISS Class 4-9 10-19 5*20
87.3 40.5 10.7
9.4 49.4 53.3
3.1 8.9 15.7
0.2 1.2 20.3
100.0 100.0 100.0
All head trauma
72.9
19.7
5.2
2.2
100.0
The Findings This is thefirstpopulation-based study of head trauma in France. As already stated the comparison of our results with those of studies carried out in other countries is difficult, since many differences exist in
definition and case ascertainment, time and place of study and analysis. We selected three studies which seemed comparable to ours in definition and case ascertainment and were confined to a defined geographical area (San Diego County9 and Olmsted County2 in the United States) or to a whole country (Great Britain).8 As shown in Table 6, the 1986 incidence rate in Aquitaine of 281/100 000 is similar to that reported in San Diego, intermediate between those of England and Scotland (not including deaths) and higher than that of Olmsted County. Klauber9 explained the higher rates in San Diego than in Olmsted County by a more complete case ascertainment in the prospective California study, compared to the retrospective study of Olmsted County. As our study was also prospective, it could explain the higher rates in Aquitaine. Actually, the mortality rates from head trauma, which are less likely to be affected by the problem of ascertainment, are similar between the three studies (Table 6). Mortality rates in Great Britain are substantially lower, but the proportion of deaths attributable to accidents is lower in Great Britain than in most other countries.8 This is partly related to the lower incidence of deaths from traffic accidents.19 The proportion of mild head trauma (80% of hospitalized cases) was similar to that reported in Scotland" and higher than that in Olmsted County (65%).2 A likely explanation is tnat fewer patients with mild injuries are admitted to hospitals in the United States than in France and Great Britain.8 Although these trauma generally require only a few days of hospitalization, the workload involved in their care is important given their large number. Patterns of incidence by age and sex, and male to female incidence ratio are in general agreement with findings from earlier studies.2-5'8"10 While the greatest peak of incidence is always reported between 15 and 24 years of age, due to traffic accidents, children and the elderly also appear to be at higher risk because of falls
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lack of appropriate diagnostic facilities in some hospitals. Another point deserving mention is the classification of head traumas into three groups of increasing severity: mild, moderate and severe. Several studies have adopted such a classification, but there is lack of uniformity in the definition of groups. Whitman" and Annegers2 used a classification combining the level of consciousness and the type of lesions. We adopted a similar classification, but with different bounds of level of consciousness. In particular, our class of severe, including comas longer than six hours, is larger than in Whitman's" and Annegers's2 studies (both included comas longer than 24 hours). The limit of six hours was adopted here to relate to the Glasgow Coma Scale (GCS), which is assessed over the sixth hour. Kraus10 and Miller" applied the GCS but not with the same bounds of classes. The GCS18 is now widely used to assess the severity of head injury. Although there are a number of limitations in its application,10 this grading system undoubtedly constitutes a useful tool for clinical and epidemiological purposes. However, our study focused initially on all injuries, and for that reason, we adopted the AIS, which is a general classification of injury severity, at the expense of scales concerning more specific problems. However, comparing our classification of severity with the GCS, we can say that our class of mild head trauma roughly corresponds to the 'mild' GCS class (score = 13 or more), whereas our class of severe is broader than the 'severe' GCS class (score = 8 or less), since it also includes brain injuries not necessarily associated with a coma at the sixth hour.
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EPIDEMIOLOGY OF HEAD TRAUMA TABLE 6
Incidence rales of head trauma from four selected studies
Population
Field of study
Sex
Aquilaine France 1986
Hospital admissions and immediate deaths
Both Male Female
281 384 184
22.3* 33.4* 11.9*
San Diego USA 1978
Hospital admissions and all deaths
Both Male Female
295
22.3 31.8 12.1
Great Britain 1974
Hospital admissions
Both Both
270 (England) 313 (Scotland)
Olmsted County USA 1935-74
Hospital admissions and all deaths
Male Female
274 116
Incidence rate/100000
Death rate/100000
9.2* 9.3* 35.0 10.0
experienced at these ages. The rate in 15-24 year agegroup males is similar in Aquitaine (750/100 000) to that reported in San Diego.9 In actual fact, mortality from traffic accidents is nearly the same in both countries." As in previous studies, mortality from head trauma increased with age.2'8'10 In our study, 4.4% of head trauma was immediately fatal. This proportion is similar to that in San Diego (4.8%).9 The case-fatality rate of patients admitted to hospital in Aquitaine was 2.2% within eight days. We assessed, on the basis of routine mortality statistics,20 that the total case-fatality rate (not limited to eight days) of hospitalized patients would be about 3.8%. This value is intermediate between those reported in other studies5910 which ranged from 3% to 6%. This implies that about 60% of hospital deaths would occur within eight days of admission. Uniquely this report describes the epidemiology of head trauma-associated injuries and the assessment of overall severity of head-injured patients, using the ISS. This global approach to the head-injured patient is relevant, since most of them sustain multiple injuries, as shown in Table 3. The treatment of injuries other than head trauma add considerably to the workload of services involved in their care, and they contribute to prolonging the hospital stay of many cases with mild head trauma. As expected, the ISS was predictive of the outcome within eight days. In the group of patients having an ISS above 20, in-hospital mortality was very high (20%). With regard to the length of hospitalization, there was a frontier between scores under and above ten. In the former group, only 10% of patients were still hospitalized at the eighth day, whereas this proportion was 50% in the latter group. In conclusion, this study shows that the problem of head trauma is of similar magnitude in France and in
Anglo-Saxon countries, despite likely differences in environmental and cultural factors, prevention policies and organization of health care systems. Further improvements must be accomplished in the prevention of head trauma, especially in the 15-24 year age group. Besides severe head trauma, which often leads to death or serious impairment, the great number of mild head trauma, which may have neurological and behavioural sequellae1016 constitute a major matter of concern for public health. ACKNOWLEDGEMENTS This study was supported by the 'Direction Regionale des Affaires Sanitaires et Sociales d'Aquitaine', the 'Conseil Regional d'Aquitaine', the 'Caisse Regionale d'Assurance Maladie d'Aquitaine', the 'Ministere de l'Equipement, du Logement, de PAmenagement du Territoire et des Transports (Securite Routiere)' and the 'Ministere de l'lnterieur (Securite Civile)'. The authors gratefully acknowledge the cooperation given by the institutions who participated in the study. They also wish to thank E Michel and V Lambert for computer programming, C Cretaz for collecting death certificates and B Mrabet and D Rebeyrol for supervising the data collection in institutions. REFERENCES ' Anderson D W. Miller J D. Kalsbeek W D. Findings from a major US survey of persons hospitalized with head injuries. Pub Hlth Rep 1983; 98: 475-8. 2 Annegers J F, Grabow J D, Kurland L T, Laws E R. The incidence, causes and secular trends of head trauma in Olmsted County, Minnesota, 1935-1974. Neurology 1980; 30: 912-9. ' Cooper K D, Tabaddor K, Hauser W A, Shulman K, Feiner C, Factor P R. The epidemiology of head injury in the Bronx. Neuroepidemiol 1983; 2: 70-88. ' Edna T H, Cappelen J. Hospital admitted head injury. A prospective study in Trondelag, Norway, 1979-80. ScandJSoc Med 1984; 12: 7-14.
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•Rates drawn from mortality statistics, including all deaths.
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Tiret L, Garros B, Maurette P, etal. Incidence, causes and severity of injuries in Aquitaine (France). A community-based study of hospital admissions and deaths. Am J Publ Health 1989; 79: 316-21. 14 Committee on Injury Scaling: The Abbreviated Injury Scale (AIS), 1980 revision. American Association for Automotive Medicine, Morton Grove, IL, 1980. 15 Baker S P, O'Neill B, Haddon W, Long W B. The Injury Severity Score: A method for describing patients with multiple injuries and evaluating emergency care. J Trauma 1974; 14: 187-96. 16 Fife D. Head injury with and without hospital admission: Comparisons of incidence and short-term disability. Am J Pub Hlth 1987; 77: 810-2. "Miller J D, Jones P A. The workload of a regional head injury service. Lancet 1985; 1: 1141^1. '8Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet 1974; 2: 81—4. "World Health Organization. World Health Statistics Annual. Geneve: 1987. 20 Statistiques des causes medicales de deces, Aquitaine, 1986. INSERM (unpublished data).
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Fife D, Faich G, Hollinshead W, Boyton W. Incidence and outcome of hospital-treated head injury in Rhode Island. Am J Pub Hlth 1986; 76: 773-8. * Frankowski R F. Descriptive epidemiologic studies of head injury in the United States: 1974-1984. Adv Psychosom Med 1986; 16: 153-72. 7 Galbraith S, Murray W R, Patel A R. Head injury admissions to a teaching hospital. Scot MedJ 1977; 22: 129-32. 8 Jennett B, Mac Millan R. Epidemiology of head injury. Br Med J 1981; 282: lOl^J. ' Klauber M R, Barret-Connor E, Marshall L F, Bowers S A. The epidemiology of head injury. A prospective study of an entire community—San Diego County, California 1978. Am J Epidemiol 1981; 113:500-9. 10 Kraus J F, Black M A, Hessol N, et al. The incidence of acute brain injury and serious impairment in a defined population. Am J Epidemiol 1984; 119: 186-201. " Whitman S, Coonley-Hoganson R, Desai B T. Comparative head trauma experiences in two socioeconomicalfy different Chicago-area communities: A population study. Am J Epidemiol 1984; 119: 570-80. 12 Fife D, Jagger J. The contribution of brain injury to the overall injury severity of brain-injured patients. J Neurosurg 1984; 60: 697-9.
