Ten-Year Trends of Adult Trauma Patients in Denmark from 2010 to 2019: A Retrospective Cohort Study

doi:10.21203/rs.3.rs-871619/v1

Background: Trauma causes a considerable economic and societal burden and the trauma patient population and its prognosis changes over time. The aim of this study is to analyze ten-year trends of trauma patients at a major trauma center in Denmark.

Methods: 5366 patients aged ≥ 16 years with Injury Severity Score (ISS) > 0 admitted by trauma team activation at Aarhus University Hospital Trauma Center between January 1, 2010 and December 31, 2019 were included. Descriptive statistics, incidence rate calculation, parametric and non-parametric test were used. An annual percent change with 95% confidence interval was used to estimate trend in mechanism of injuries. Multiple logistic regression with mortality as outcome were adjusted for age, sex and ISS.

Results: The median age increased from 37 in 2010 to 49 in 2019 and the proportion of patients aged ≥ 65 doubled. The incidence of minor injuries (ISS 1-15) decreased from 181.3/10⁵ inhabitants in 2010 to 112.7/10⁵in 2019 corresponding to an incidence rate ratio between 2019 and 2010 of 0.62 (95% CI: 0.54 to 0.72). Severe injuries (ISS > 15) increased from 10.1/10⁵ inhabitants in 2010 to 13.6/10⁵ in 2019 corresponding to an incidence rate ratio between 2019 and 2010 of 1.35 (95% CI: 1.04 to 1.76). The proportion of patients with ISS > 15 increased from 18.1% in 2010 to 31.1% in 2019. Multivariable logistic regression showed lower 30-day mortality for all trauma patients with ISS > 0 over the study period when adjusting for age, sex and ISS (Odds ratio: 0.94, 95% CI: 0.90 to 0.99). The 30-day mortality for severely injured patients with ISS > 15 decreased during the study period when adjusting for age, sex and ISS (Odds ratio: 0.92, 95% CI: 0.87 to 0.97). Fall injuries increased with an annual percent change of 4.1% (95% CI: 2.3% to 6.1%).

Conclusions: Ten-year trends of trauma patients in Central Denmark Region show an increasing median age, injury severity and number of fall injuries. The 30-day mortality of trauma patients decreased for both minor injuries and severe injuries when adjusting for age, sex and injury severity.

Trial registration: Not applicable.

Critical Care & Emergency Medicine

Trauma

Injury

Denmark

Trend

Severe Injury

Scandinavia

Mechanism

Epidemiology.

Injuries and trauma account for 8% of global mortality and cause considerable loss of quality of life.(1–4) Trauma is the leading cause of death among young people and creates a substantial economic and societal burden related to subsequent disabilities and loss of potential years of life.(2, 5) The pattern of injuries in Scandinavia are predominantly traffic related, fall injuries, and blunt trauma and differ from other countries by having lower rates of gunshot wounds and penetrating injuries.(6–8) In 2018, trauma patients caused 2405 admissions to major Danish trauma centers of whom 6.8% died within 30 days.(3) Frequent causes of death in Denmark among trauma patients was found to be damage to the central nervous system, exsanguination and multiple organ failure.(8, 9) Characterizing and analyzing trauma patients in terms of epidemiology, patient demographics, interventions and outcome consecutively can enhance trauma care, identify preventable injuries and describe tendencies through time.(6) To date, several studies have investigated long-term trauma trends in USA, Japan and UK.(10–12) The changes in mechanism of injury, mortality and demographics were highlighted in previous studies and particularly a rise in fall injuries and increasing age were among the compelling findings.(11, 12) Moreover, it is now well established that trauma mortality is changing due to demographic alterations and the increasing proportion of elderly trauma patients and their higher mortality.(6, 13) The impact of long-term changes in the Danish trauma population have not been investigated in recent years. Trauma registries hold the potential for analysis and comparison of injury prevention measures and benchmarking across regions and countries.(6) We have registered trauma patients for many years at Aarhus University Hospital Trauma Center. Hence, the aim of this study is to benchmark and analyze ten-year trends of trauma patients in Central Denmark Region with focus on epidemiology, severity, mortality and the mechanism of injury (MOI). We will further investigate the subgroup of patients with severe injuries (Injury Severity Score [ISS] > 15).

This study is a retrospective cohort study in a ten-year period from 2010 to 2019 at a major trauma center in Denmark. The study complied to the STROBE guidelines.(14)

Setting and data collection

The Aarhus University Hospital Trauma Registry (AUH-TR) is the trauma registry of Aarhus University Hospital Trauma Center (AUH-TC). AUH-TC is a tertiary trauma center with highly specialized surgery and critical care. The catchment area for minor injuries covers Aarhus municipality (population 350,000) along with major trauma patients from Central Denmark Region (population 1.3 million).(15) Exact population count for incidence calculations were collected retrospectively at the public accessible Danish Statistics website.(16) The annual number of trauma team activations (TTA) at AUH-TC is approximately 600 and more than 150 of these patients are severely injured (ISS > 15).(3) AUH-TC is the referral trauma center for 4 regional acute-care hospitals in Central Denmark Region. Minor injuries without TTA treated in the Emergency Department (ED) and at acute-care hospitals are not included in AUH-TR. The pre-hospital emergency medical service in Central Denmark Region contains 69 ambulances (staffed by a paramedic and an emergency medical technician) and 10 rapid response vehicles (staffed by a paramedic and an anesthesiologist). The national helicopter service consists of four helicopter emergency medical service (HEMS) bases staffed with 24 h per day anesthesiologist and paramedic. The prehospital unit requests TTA according to predefined criteria (Table S1 in the supplementary material). TTA involve a minimum of 10 professionals including an anesthesiologist, orthopedic surgeon, emergency physician, nurse anesthetist, trauma nurse, medical laboratory technologist, radiographer, medical secretary, supporting staff and physicians or surgeons from relevant medical specialties. Data collection for AUH-TR is performed by hospital administrative staff during treatment of the patient. Data in AUH-TR includes patient demographics, injury description, timeline, ISS, and MOI. MOI is categorized by road traffic collision, scooter, motorcycle, bicycle, fall, horse, pedestrian, violence, stabbing, self-harm, gunshot, and other mechanism such as animal-related injuries, crushing, struck by object, machinery accidents, sports injuries or other miscellaneous injuries. Fall injuries include falls from all heights.

Outcome

Danish trauma centers use Abbreviated Injury Scale (AIS) to score each injury sustained by trauma patients.(17, 18) The ISS is calculated based on the assigned AIS scores done by AIS certified physicians and medical students. To avoid interpersonal discrepancy between AIS scores assigned, the coding team regularly discussed cases and reviewed the process of assigning codes to assure consistency. Severe injury was defined as ISS > 15. Data for 30-day mortality was retrieved from patient’s medical record using the Danish Civil Registration number (CRS). The Danish Civil Registration system contains vital status for all Danish citizens along with non-citizens who reside in Denmark.(19)

Patients

Trauma patients admitted to AUH-TC with ISS > 0 and aged ≥ 16 were included in the analyses. Figure 1 shows patient inclusion and exclusion for the study. Patients with major trauma initially admitted to an acute-care hospital with secondary transfer to AUH-TC within 24 hours were also included.

Statistics

Descriptive data were reported as numbers and percentages. Continuous data were reported as mean and standard deviation for normally distributed data, and median and interquartile range (IQR) for non-normal distributed data. Comparison of groups for normally distributed data was performed by t-test and for non-normal distributed data utilizing the Mann-Whitney U-test. Non-parametric comparison over time for ISS and age were performed by Kruskal-Wallis test. A Chi-square test was used to compare distribution of categorical variables. Incidence rates were calculated using catchment area population count separately for Aarhus Municipality (ISS 1–15) and Central Denmark Region (ISS > 15).(16) An average linear trend in the change of MOI proportions during the ten-year study period was calculated by logistic regression with year as a continuous independent variable. This computed the estimated annual percent change (APC) of MOI with 95% confidence interval. Logistic regression with 30-day mortality as outcome adjusted for age, sex and ISS were calculated. STATA version STATA/IC 17.0 (StataCorp. 2019. Texas, USA) was used for all statistical analyses. A two-sided P-value of < 0.05 was considered statistically significant.

Ethics and approvals

This study was a registry study and exempted from trial registration according to Danish law due to the anonymity of the data. The hospital board of directors approved the study.

During the study period, 5366 adult trauma patients aged ≥ 16 with ISS > 0 between January 1, 2010 and December 31, 2019 were included (Fig. 1). Patient characteristics and outcomes are seen in Table 1. Median age increased significantly from 37 years in 2010 to 49 years in 2019 (Fig. 2). Fig. 2 provides visualization of how the age distribution changed in 2010, 2015 and 2019. The proportion of patients aged ≥ 65 increased significantly from 11.7% (n = 65) in 2010 to 23.5% (n = 111) in 2019 (Table 1).

Table 1: Patient characteristics and outcomes from 2010-2019.

	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	p-value
Patients, n	558	542	537	492	605	468	532	601	559	472
Male, n (%)	375 (67.2)	373 (69.0)	352 (65.7)	334 (68.0)	392 (65.3)	298 (65.2)	355 (67.0)	398 (66.8)	408 (73.0)	319 (67.7)	0.239 ^a
ISS, n > 15 (%)	101 (18.1)	137 (25.4)	95 (17.7)	101 (20.5)	139 (23.0)	138 (29.5)	148 (27.8)	163 (27.1)	169 (30.2)	147 (31.1)	< 0.01 ^a
ISS, Median	5	8	5	5	5	9	8	8	9	9	< 0.01 ^b
ISS > 15, Median	22	24	22	25	24	24	22	25	25	24	0.353 ^b
Age, Median (IQR)	37 (24 to 53)	39 (25 to 52.5)	38 (25 to 54)	42 (26 to 57)	41 (25 to 55)	42 (26 to 57)	43 (25 to 59)	41 (25 to 58)	45 (27 to 61)	49 (27 to 63)	< 0.01 ^b
Age, n 16-34 (%)	244 (44.0)	228 (42.2)	235 (43.9)	195 (39.7)	248 (41.3)	183 (39.4)	200 (37.7)	244 (40.8)	199 (35.6)	159 (33.7)	< 0.01 ^a
Age, n 35-64 (%)	246 (44.3)	233 (43.2)	225 (42.1)	224 (45.6)	270 (44.9)	207 (44.5)	230 (43.3)	239 (40.0)	234 (41.9)	202 (42.8)
Age, n ≥ 65 (%)	65 (11.7)	79 (14.6)	75 (14.0)	72 (14.7)	83 (13.8)	75 (16.1)	101 (19.0)	115 (19.2)	126 (22.5)	111 (23.5)
30-day mortality, n (%)	20 (3.6)	37 (7.0)	30 (5.8)	31 (6.4)	29 (4.9)	33 (7.2)	23 (4.4)	27 (4.6)	36 (6.7)	34 (7.4)	0.065 ^a
30-day mortality ISS > 15, n (%)	16 (15.8)	32 (23.5)	24 (25.5)	27 (27.0)	25 (18.5)	26 (19.1)	18 (12.3)	24 (15.1)	26 (16.1)	28 (19.6)	0.093 ^a
30-day mortality age 16-64, n (%)	10 (2.1)	15 (3.4)	18 (4.1)	20 (4.8)	18 (3.5)	18 (4.7)	9 (2.1)	8 (1.7)	18 (4.3)	12 (3.4)	0.080 ^a
30-day mortality age ≥ 65, n (%)	10 (15.4)	22 (28.2)	11 (15.1)	11 (15.3)	10 (12.2)	15 (20.0)	14 (14.0)	19 (16.7)	18 (14.8)	22 (20.0)	0.277 ^a
CT scan, n (%)	Missing					367 (89.3)	459 (86.4)	531 (88.7)	501 (90.0)	425 (90.4)	0.279 ^a
CT scan ISS > 15, n (%)	Missing					102 (85.7)	121 (82.3)	133 (81.6)	150 (89.8)	130 (89.0)	0.122 ^a
ISS = Injury Severity Score. CT = Computed Tomography imaging. ^a Chi-square test. ^b Kruskal-Wallis test. Missing Danish Civil Registration number in 2010 (n = 4), 2011 (n = 16), 2012 (n = 19), 2013 (n = 4), 2014 (n = 11), 2015 (n = 12), 2016 (n = 6), 2017 (n = 12), 2018 (n = 18), 2019 (n = 11). Missing CT-scan in 2015 (n = 57), 2016 (n = 1), 2017 (n = 2), 2018 (n = 2), 2019 (n = 2).

The incidence of minor injuries (ISS 1-15) decreased from 181.3/10⁵ inhabitants (95% CI: 165.1 to 198.7) in 2010 to 112.7/10⁵ (95% CI: 100.8 to 125.6) in 2019 (Table S2). The incidence rate ratio of minor injuries between 2019 and 2010 were 0.62 (95% CI: 0.54 to 0.72). The incidence of severe injuries (ISS > 15) increased from 10.1/10⁵ (95% CI: 8.2 to 12.3) in 2010 to 13.6/10⁵ (95% CI: 11.5 to 16.0) in 2019 (Table S2). The incidence rate ratio of severe injuries between 2019 and 2010 were 1.35 (95% CI: 1.04 to 1.76). The severity of the trauma patient population at AUH-TC changed as the proportion of patients with ISS > 15 increased significantly from 18.1% in 2010 to 31.1% in 2019 (Table 1, Fig. 3, Fig. S1). AIS distribution from 2014-2019 is available in Table S3.

Mortality

The 30-day mortality of all patients were 3.6% in 2010 and 7.4% in 2019 (Table 1). The 30-day mortality of patients with ISS > 15 were 15.8% in 2010 and 19.6% in 2019 (Table 1). In multivariate regression analyses (Table 2, Table S4), the 30-day mortality for all patients decreased from 2010 to 2019 when adjusting for age, sex and ISS (Odds ratio: 0.94, 95% CI: 0.90 to 0.99). Additionally, the 30-day mortality for patients with ISS > 15 decreased from 2010 to 2019 when adjusting for age, sex and ISS (Odds ratio: 0.92, 95% CI: 0.87 to 0.97). The odds ratio for 30-day mortality were 8.92 for patients aged ≥ 65 (95% CI: 6.36 to 12.50) compared to patients aged 16-34.

Table 2: Multivariable logistic regression analysis for 30-day mortality of trauma patients.

	All patients, n = 5253		Patients with ISS > 15, n = 1312
	OR (95% CI)	p-value	OR (95% CI)	p-value
Age	1.05 (1.04 to 1.06)	< 0.01	1.03 (1.03 to 1.04)	< 0.01
16-34	Reference		Reference
35-64	1.98 (1.39 to 2.81)	< 0.01	1.35 (0.90 to 2.01)	0.142
≥ 65	8.92 (6.36 to 12.50)	< 0.01	4.00 (2.72 to 5.89)	< 0.01
Sex, male	1.05 (0.82 to 1.36)	0.683	0.78 (0.58 to 1.05)	0.106
ISS	1.11 (1.10 to 1.12)	< 0.01	1.07 (1.06 to 1.09)	< 0.01
Year (2010-2019)	1.02 (0.98 to 1.07)	0.267	0.95 (0.91 to 1.00)	0.059
Year adjusted for age	0.98 (0.94 to 1.02)	0.328	0.93 (0.89 to 0.98)	0.007
Year adjusted for sex	1.02 (0.98 to 1.06)	0.281	0.95 (0.91 to 1.00)	0.050
Year adjusted for ISS	0.97 (0.93 to 1.02)	0.266	0.94 (0.89 to 0.99)	0.026
Year adjusted for age, sex and ISS	0.94 (0.90 to 0.99)	0.012	0.92 (0.87 to 0.97)	0.002
OR = Odds ratio. ISS = Injury Severity Score. CI = Confidence Interval. Missing Civil Registration number in 2010 (n = 4), 2011 (n = 16), 2012 (n = 19), 2013 (n = 4), 2014 (n =11), 2015 (n = 12), 2016 (n = 6), 2017 (n = 12), 2018 (n =18), 2019 (n = 11).

Mechanism of injury

Proportions of MOI changed during the ten-year study period (Table 3). The 95% CI indicate significant increases in the annual percent change (APC) in fall injuries of 4.1% (95% CI: 2.3% to 6.1%). Contrary, we found significant APC decreases in pedestrian injuries by -4.7% (95% CI: -8.6% to -0.7%) and violence -14.0 (95% CI: -18.7% to -8.9%).

Table 3: Trends in mechanism of injury from 2010-2019.

	2010, n (%)	2011, n (%)	2012, n (%)	2013, n (%)	2014, n (%)	2015, n (%)	2016, n (%)	2017, n (%)	2018, n (%)	2019, n (%)	APC ^a (95% CI)
Road traffic collision	181 (37.8)	157 (30.5)	171 (33.0)	118 (24.6)	167 (27.6)	151 (32.6)	191 (35.9)	189 (31.5)	167 (29.9)	143 (30.3)	-0.7 (-2.1 to 0.7)
Motorcycle	23 (4.8)	33 (6.4)	19 (3.7)	29 (6.1)	41 (6.8)	23 (4.9)	31 (5.8)	27 (4.5)	35 (6.3)	27 (5.7)	-0.9 (-3.0 to 5.0)
Scooter	32 (6.7)	23 (4.5)	23 (4.4)	26 (5.4)	29 (4.8)	27 (5.8)	24 (4.5)	28 (4.7)	13 (2.3)	15 (3.2)	-6.0 (-10.0 to -1.8)
Bicycle	50 (10.4)	71 (13.8)	77 (14.8)	93 (19.4)	117 (19.3)	61 (13.0)	59 (11.1)	81 (13.5)	75 (13.4)	79 (16.7)	0.4 (-1.9 to 2.8)
Fall	86 (18.0)	103 (20.0)	97 (18.7)	90 (18.8)	126 (20.8)	94 (20.1)	126 (23.7)	139 (23.1)	150 (26.8)	116 (24.)	4.1 (2.3 to 6.1)
Horse	12 (2.5)	20 (3.9)	22 (4.2)	23 (4.8)	21 (3.5)	14 (3.0)	12 (2.3)	24 (4.0)	17 (3.0)	12 (2.5)	-2.6 (-7.4 to 2.5)
Pedestrian	23 (4.8)	27 (5.3)	45 (8.7)	27 (5.6)	30 (5.0)	15 (3.2)	27 (5.1)	32 (5.3)	28 (5.0)	12 (2.5)	-4.7 (-8.6 to -0.7)
Violence	31 (6.5)	29 (5.6)	8 (1.5)	18 (3.8)	15 (2.5)	15 (3.2)	16 (3.0)	12 (2.0)	9 (1.6)	6 (1.3)	-14.0 (-18.7 to -8.9)
Stabbing	11 (2.3)	15 (2.9)	14 (2.7)	18 (3.8)	14 (2.3)	18 (3.9)	14 (2.6)	24 (4.0)	24 (4.3)	22 (4.7)	6.8 (1.4 to 12.5)
Gunshot	4 (0.8)	1 (0.2)	1 (0.2)	1 (0.2)	2 (0.3)	4 (0.9)	2 (0.4)	6 (1.0)	3 (0.5)	7 (1.5)	15.0 (0.9 to 31.1)
Self-harm	8 (1.7)	7 (1.4)	6 (1.2)	8 (1.7)	7 (1.2)	13 (2.8)	6 (1.1)	9 (1.5)	7 (1.3)	7 (1.5)	-0.3 (-7.8 to 7.7)
Other mechanism^b	18 (3.8)	28 (5.5)	36 (6.9)	28 (5.9)	36 (6.0)	33 (7.1)	24 (4.5)	30 (5.0)	31 (5.6)	27 (5.7)	0.0 (-3.5 to 4.4)
^aAverage annual percent change. ^bOther mechanism of injuries includes crushing, struck by object or sports injuries. Mechanism of injury were missing in 2010 (n = 79), 2011 (n = 28), 2012 (n = 18), 2013 (n = 13).

The 30-day mortality in each of the MOI categories for all years are seen in Table S5. The largest change in MOI over the years were fall injures and fall injuries accounted for the highest number of fatalities and had a 30-day mortality of 9.7% (n = 106), Table S5.

Transport

Transport and admission data were available from 2015-2019. The proportion of trauma patients transferred from other hospitals decreased numerically from 11.3% (n = 53) in 2015 to 7.6% (n = 36) in 2019 (Table S6). The proportion of patients admitted directly from surrounding municipalities increased numerically from 43.4% (n = 165) in 2015 to 51.2% (n = 233) in 2019. The proportion of patients with ISS > 15 admitted directly from surrounding municipalities were 65.4% (n = 70) in 2015 and increased numerically to 78.0% (n = 110) in 2019. The proportion of patients admitted by HEMS increased numerically from 10.3% (n = 48) in 2015 to 13.4% (n = 63) in 2019.

This study investigates ten-year trends of demographics, injury severity, 30-day mortality and MOI among trauma patients in Central Denmark Region. We found an increase in the median age and the proportion of patients aged ≥ 65 doubled. The incidence and proportion of severely injured patients (ISS > 15) increased as well as the median ISS throughout the study period. The crude 30-day mortality of all patients and patients with severe injuries did not change despite an increase in injury severity but did, however, decrease when adjusting for age, sex and ISS. Long-term trends in mechanism of injuries displayed a significant increase in fall injuries.

Changing demographics

We found the median age of adult trauma patients admitted at AUH-TC to peak at 49 years in 2019. Furthermore, we found an increase in the proportion of patients aged ≥ 65. Ageing of the trauma patient population corroborate with numerous previous trauma studies worldwide.(10–12) In a previous study from AUH-TC, the median age of all trauma patients increased from 29 to 32 in the timeframe from 2000–2008.(20) These results suggest an accelerated aging of the trauma patient population in Central Denmark Region. Kehoe et al. studied major trauma from 1990 to 2013 in the UK and described how the mean age of major trauma patients have ascended from 36.1 to 53.8 and the proportion of patients aged ≥ 75 increased from 8.1–26.9%.(12) Pre-existing medical conditions as diabetes mellitus, obesity, heart disease and hypertension are more frequent and contribute to morbidity in elderly trauma patients.(21) In Norway, Cuecas-Østrem et al. studied geriatric trauma patients nationwide from 2015–2018. They included adult trauma patients with New Injury Severity Score ≥ 9 and older than 16 and compared to patients aged ≥ 65 years. Geriatric trauma patients in that study had a 30-day mortality of 13.6% compared to 2.6% of patients aged between 16–64 years. A study from Germany found increased mortality independent of ISS from age ≥ 56 in severely injured elderly trauma patients.(22) A nationwide study of the causes of death in Sweden reported a decline in mortality by injury in the group of working age but an increase among elderly patients.(13) Collectively, these studies highlight the frailty and excess mortality of elderly trauma patients and the need for an increased focus on this age group.(13, 23)

Injury severity

We found an increasing injury severity and the proportion of severely injured patients with ISS > 15 climbed from 18.1% in 2010 to a maximum of 31.1% in 2019. The median ISS of severely injured patients (ISS > 15) was 24 in 2019 at AUH-TC. The proportion of patients with ISS > 15 were 33.9% at a major trauma center in Norway and 21.1% at a major trauma center in Sweden in the period from 2009–2011.(24) When compared with other major trauma centers, the median ISS of trauma patients with ISS > 15 were 17 in Spain, 24 in Hong Kong and between 22 and 25 in TraumaRegister DGU® (TR-DGU).(25, 26)

Mortality

In 2019, we observed a 7.4% crude 30-day mortality of patients aged ≥ 16 years with ISS > 0. We did identify a survival benefit in the time between 2010 and 2019 when adjusting for age, sex and ISS. We calculated an odds ratio for 30-day mortality of 8.92 among patients aged ≥ 65 compared to patients aged 16–34. When focusing on Central Denmark Region, Mikkelsen et. al studied trauma patients admitted to AUH-TC from 2000–2011 and found a 4.4% mortality and no improved survival during the study period.(27) However, they did not specify an ISS inclusion or exclusion criteria of patients with missing CRS.(27) An initial objective of the present study was to benchmark and compare trauma care at AUH-TC to other major trauma centers. An obstacle is the inconsistency of inclusion and exclusion criteria in the research of trauma patients. In a Scandinavian study of trauma patients with ISS > 0 and older than 15 years they observed a 30-day mortality of 5.6% in Norway and 3.2% in Sweden.(24) Additionally, a Swedish study from 2013–2017 found a 4.6% 30-day mortality among trauma patients with ISS > 0 of all ages treated at major trauma centers.(28) In a Japanese nationwide trauma registry study from 2004–2013. The adjusted in-hospital mortality of adult trauma patients with ISS > 3 decreased annually during the study period.(11) In terms of severe injuries, we found a 19.6% crude 30-day mortality of patients aged ≥ 16 years with ISS > 15. Several European studies(7, 25, 29) and a study from Hong Kong(26) have showed a 30-day mortality of trauma patients with ISS > 15 varying between 14.9% and 22.4%. In Japan, the in-hospital mortality of adult trauma patients with ISS ≥ 16 decreased from 28.5% in 2004 to 15.7% in 2013.(11) The crude 30-day mortality varies substantially between major trauma centers although our crude 30-day mortality is comparable to the before mentioned studies.

Mechanism of injury

We found a significant APC increase in fall injuries of 4.1%. We found a decreasing APC in pedestrian injuries of -4.7% and in scooter injuries of -6.0%. Large numbers of studies have also reported increasing numbers of falls and especially in patients aged ≥ 65.(10–12, 30) In UK, the proportion of fall injuries < 2 m among severely injured patients increased from 4.7% from 1990 to 39.1% in 2013.(12) Ten-year trends from 2005–2014 in a statewide trauma registry in Oklahoma, USA, found the APC of fall injuries to increase by 4.0% (95% CI: 3.1–4.9%) and the number of fall injuries among patients ≥ 65 more than doubled. Furthermore, the APC of pedestrian injuries decreased by -1.5% during the ten-year study period in that trauma patient population.(10) We found APC increases in stabbings of 6.8% and gunshot of 15.0% but decreases in violence of -14.0%. Twenty-year trends of trauma patients in the UK found the proportion of gunshot and stabbing combined to increase from 0.2% in 1990 to 1.9% in 2013.(12)

Centralization of trauma care

In this study, a greater part of severely injured patients was admitted directly from surrounding municipalities and less patients were transferred in the timeframe from 2015 to 2019. The increasing injury severity and proportion of patients with ISS > 15 during the study period suggests that more severely injured trauma patients are admitted directly to AUH-TC from other parts of Central Denmark Region. An explanation for the growth in proportions of severe injuries at AUH-TC could be centralized trauma care, enhanced transport and improved triage, meaning that severely injured patients are transported directly to the highest level of expertise at the major trauma center. Moreover, the national HEMS were introduced in 2014 and contributed to an extension of the catchment area. In accordance with the present results, Brink et al. found that the percentage of transferred patients to AUH-TC increased from 3.9% in 2000 to 13.4% in 2008.(20) In Sweden, Candefjord et al. found a survival benefit for severely injured patients treated at trauma centers compared with non-trauma centers. The mortality risk decreased 41% for trauma patients with ISS > 0 and 70% for the most critical injured patients (ISS ≥ 50).(28) This finding is consistent with a study from Japan, that found reduced in-hospital mortality of severe trauma patients in high volume trauma centers (≥ 100 annual patients with ISS > 15) compared to low volume trauma centers (1–49 annual patients with ISS > 15).(31) The centralization of major trauma may contribute to the improvement of trauma care by a higher volume strategy and a higher degree of specialization.

Strengths and limitations

We included long-term trends in mortality. The percentage of missing patients is low and most major trauma patients in Central Denmark Region (22% of the Danish population) are admitted to AUH-TC.(16) Our study however has potential limitations that affect the interpretation. The limited numbers of trauma patients in Denmark challenges comparison to other major trauma centers. We did detect significant changes in MOI, but the number of patients in each category of MOI were limited thus complicating the identification of long-term trends. Studies have shown inter-rater discrepancies in AIS scores, however it is rare that these discrepancies affect the ISS.(32) Even though the TTA criteria remained the same, the emergency physician’s threshold to activate the trauma team could have changed during the study period. The implementation of national HEMS in 2014 and centralization may have enlarged the catchment area. In 2018, Weile et al. found heterogenous composition of the trauma team and TTA criteria at trauma facilities in Denmark(33) and some major trauma patients are still treated at acute-care hospitals in Central Denmark Region. A national benchmark study including the entire Danish trauma patient population is warranted.

Investigating and using long-term trends is necessary to benchmark trauma care and adapt to the aging trauma patient population. In this single center ten-year retrospective cohort study, we observed an increasing injury severity and proportion of elderly but unchanged crude 30-day mortality. The incidence of minor injuries decreased contrary to a rise in incidence of severe injuries. Age, sex and injury severity adjusted survival improved from 2010 to 2019. Fall injuries are significantly increasing and trauma team activations with patients aged ≥ 65 doubled from 2010–2019.

AIS: Abbreviated Injury Scale

APC: Annual percent change

AUH: Aarhus University Hospital

AUH-TR: Aarhus University Hospital Trauma Registry

AUH-TC: Aarhus University Hospital Trauma Center

CRS: Danish Civil Registration

GCS: Glasgow Coma Scale

HEMS: Helicopter emergency services

ISS: Injury Severity Score

MOI: Mechanism of Injury

RTC: Road traffic collision

TR-DGU: TraumaRegister DGU^®

TTA: Trauma team activation

Ethics approval: Not applicable.

Consent for publication: Not applicable.

Availability of data and materials: Not applicable.

Competing interest: The authors declare that they have no competing interests.

Funding: Department funding only.

Author contributions: FT, HK, JF, NR, AR and RS designed this study. FT, HK, JF and RS contributed to data collection. FT, HK and JF performed the data analysis and interpretation of data. FT wrote the manuscript. HK, JF, NR, AR, RS critically revised the manuscript. All authors approved the final manuscript.

Acknowledgements: We thank all personnel at Aarhus University Hospital Trauma Center who collected the data to Aarhus University Hospital Trauma Registry. We thank Jens Aage Kølsen Petersen for commenting the manuscript.

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STROBEchecklisttenyeartrends.docx
figuresS1.pdf
Figure S1: The 30-day mortality of all patients from 2010 to 2019 and the proportion of patients with ISS > 15. CI = Confidence interval. ISS = Injury Severity Score.
Supplementarytable.docx

Ten-Year Trends of Adult Trauma Patients in Denmark from 2010 to 2019: A Retrospective Cohort Study

Status:

Version 1

Abstract

Figures

Introduction

Methods

Setting and data collection

Outcome

Patients

Statistics

Ethics and approvals

Results

Discussion

Changing demographics

Injury severity

Mortality

Mechanism of injury

Centralization of trauma care

Strengths and limitations

Conclusion

Abbreviations

Declarations

References

Supplementary Files

Status:

Version 1